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  • 151.
    Khayamyan, Shervin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gustavsson, Håkan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Transition from laminar to turbulent flow in porous media2011Conference paper (Refereed)
  • 152.
    Khayamyan, Shervin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lycksam, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hellström, Gunnar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Transitional and Turbulent Flow in a Bed of Spheres as Measured with Stereoscopic Particle Image Velocimetry2017In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 117, no 1, p. 45-67Article in journal (Refereed)
    Abstract [en]

    Stereoscopic particle image velocimetry has been used to investigate inertia dominated, transitional and turbulent flow in a randomly packed bed of monosized PMMA spheres. By using an index-matched fluid, the bed is optically transparent and measurements can be performed in an arbitrary position within the porous bed. The velocity field observations are carried out for particle Reynolds numbers, (Formula presented.), between 20 and 3220, and the sampling is done at a frequency of 75 Hz. Results show that, in porous media, the dynamics of the flow can vary significantly from pore to pore. At (Formula presented.) around 400 the spatially averaged time fluctuations of total velocity reach a maximum and the spatial variation of the time-averaged total velocity, (Formula presented.) increases up to about the same (Formula presented.) and then it decreases. Also in the studied planes, a considerable amount of the fluid moves in the perpendicular directions to the main flow direction and the time-averaged magnitude of the velocity in the main direction, (Formula presented.), has an averaged minimum of 40% of the magnitude of (Formula presented.) at (Formula presented.) about 400. For (Formula presented.), this ratio is nearly constant and (Formula presented.) is on average a little bit less than 50% of (Formula presented.). The importance of the results for longitudinal and transverse dispersion is discussed.

  • 153.
    Khayamyan, Shervin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hellström, Gunnar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lycksam, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Measurements of Transitional and Turbulent Flow in a Randomly Packed Bed of Spheres with Particle Image Velocimetry2017In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 116, no 1, p. 413-431Article in journal (Refereed)
    Abstract [en]

    Particle image velocimetry (PIV) has been used to investigate transitional and turbulent flow in a randomly packed bed of mono-sized transparent spheres at particle Reynolds number, (Formula presented.). The refractive index of the liquid is matched with the spheres to provide optical access to the flow within the bed without distortions. Integrated pressure drop data yield that Darcy law is valid at (Formula presented.). The PIV measurements show that the velocity fluctuations increase and that the time-averaged velocity distribution start to change at lower (Formula presented.). The probability for relatively low and high velocities decreases with (Formula presented.) and recirculation zones that appear in inertia dominated flows are suppressed by the turbulent flow at higher (Formula presented.). Hence there is a maximum of recirculation at about (Formula presented.). Finally, statistical analysis of the spatial distribution of time-averaged velocities shows that the velocity distribution is clearly and weakly self-similar with respect to (Formula presented.) for turbulent and laminar flow, respectively

  • 154. Khayamyan, Shervin
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lycksam, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hellström, Gunnar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    PIV measurements within a randomly packed bed of spheres2016Conference paper (Refereed)
  • 155.
    Khayamyan, Shervin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Interaction between the flow in two nearby pores within a porous material during transitional and turbulent flow2015In: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 8, no 2, p. 281-290, article id 21446Article in journal (Refereed)
    Abstract [en]

    The transition from laminar to turbulent flow in porous media is studied with a pore doublet model consisting of pipes with different diameter. The pressure drop over all pipes is recorded by pressure transducers for different flow rates. Results show that the flow in the parallel pipes is redistributed when turbulent slugs pass through one of them and six different flow zones were identified by studying the difference between the Re in the parallel pipes. Each flow zone starts when the flow regime of one of the pipe changes. Transitional flow of each pipe increases the correlation between different pipes pressure drop fluctuations. Frequency analysis of the pressure drops show that the larger pipe makes the system to oscillate by the presence of turbulent patches in its flow. However, when the flow in the smaller pipe enters into the transitional zone the larger pipe starts to follow the fluctuations of the smaller pipe.

  • 156.
    Khayamyan, Shervin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gustavsson, Håkan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Experimental investigation of transitional flow in porous media with usage of a pore doublet model2014In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 101, no 2, p. 333-348Article in journal (Refereed)
    Abstract [en]

    The transition from laminar to turbulent flow in porous media is studied with a new method. To mimic inter-connected pores, a simplified geometry is studied consisting of a pipe with a relatively large diameter that is split into two parallel pipes with different diameters. This is a pore-doublet set-up and the pressure drops over the parallel pipes are recorded by pressure transducers for different flow rates. Results show that the flow in the parallel pipes is redistributed when turbulent slugs pass through one of them. The presence of the slugs is revealed by positive skewness in the pressure signals as well as an increase of the standard deviation of the pressure drops and correlation between the pressure drops of the pipes. A frequency analysis of the pressure drops show that lower band frequency pressure variations in one pipe are communicated to the other pipe while higher band frequencies are filtered out.

  • 157. Kluge, Jimmy
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ljung, Anna-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nyman, Tony
    Saab Aeronautics, SE-582 54 Linköping, SWEDEN.
    An Experimental Study of Temperature Distribution in an Autoclave2016In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 35, no 7, p. 566-578Article in journal (Refereed)
    Abstract [en]

    In this work, the temperature distribution on an industrial mold tool is monitored during autoclave runs with three settings. In one of the settings, the temperature and pressure follow a scheme used in real moldings, while in the other two cases, the temperature is increased as fast as possible with and without an applied pressure. The temperature difference over the tool is relatively large and varies between 29℃ and 76℃ validating a detailed investigation of the temperature at different points. Two results of this are that positions on the up-stream side of the tool are heated faster than positions down-stream and the heating over the tool is symmetric while that within is asymmetric. Roughly estimated heat transfer coefficients reveal that the temperature ramping has no significant effect on the local heat transfer coefficients while the applied pressure more than doubled them. In addition flow field measurements with particle image velocimetry are performed, revealing a very slow flow near the roof of the autoclave and a velocity peak near the floor of it, indicating that the flow profile within the autoclave and variation in heat transfer coefficients should be considered in autoclave simulations.

  • 158. Kluge, Jimmy
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nyman, Tony
    Saab Aeronautics, SE-582 54 Linköping, SWEDEN.
    Modelling Heat Transfer Inside an Autoclave: Effect of Radiation2016In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 35, no 14, p. 1126-1142Article in journal (Refereed)
    Abstract [en]

    In this work, computational fluid dynamics simulations are performed to predict the temperature distribution on a part during an autoclave run. Data from an experimental study are used as input to the simulations and also for comparison with the numerical results. A conjugate heat transfer approach was used for the simulations, where best agreement with experiments was obtained from the simulation that included thermal radiation and utilized an experimentally obtained velocity profile as inlet velocity. A yet more detailed inlet velocity profile and more advanced turbulent model could result in an even better agreement.

  • 159. Kluge, Jimmy
    et al.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Olofsson, Kurt
    Swerea SICOMP AB.
    Compression moulding of sheet moulding compound: Modelling with computational fluid dynamics and validation2015In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 34, no 6, p. 479-492Article in journal (Refereed)
    Abstract [en]

    Compression moulding experiments of sheet moulding compound, visual observations of a vacuum test with prepregs and numerical models with two main approaches for computational fluid dynamics simulations of the mould filling phase are presented. One assumes that there are layers near the mould surfaces with much less viscosity and the other only use one viscosity model. The numerical experiments showed that the pressure could be accurately predicted with both approaches. The property necessary to predict correct pressure with altered mould closing velocities was that the bulk material had to obey shear-thinning effects. Preheating effects before compression were neglected, but altering the heating time until the prepreg was assumed to start flow had a significant effect. The experiments confirmed that the pressure is predominantly affected by the mould closing velocity. Regardless of the considered process settings, a first pressure top always appeared approximately at the logarithmic strain 0.25. A second top was associated with a slowdown of the press. The location of this was affected by the velocity and the vacuum, the latter indicating that vacuum assistance prevents a build-up of back pressure. Furthermore, heated prepreg above a critical temperature is observed to swell immediately as vacuum assistance is applied.

  • 160.
    Knutsson, Sven
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Hellström, Gunnar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Project: Internal erosion in embankment dams2010Other (Other (popular science, discussion, etc.))
    Abstract [en]

    Since older embankment dams have a tendency to gradually display an increased degree of leakage it is interesting to find out if this phenomenon can be captured by an inverse modelling approach. Numerical tests with a model system will hopefully lead to a better understanding of the decomposition of material in dams and enhance the knowledge about the long term effects in order to forsee potential problems in the future.These embankment dams typically consist of a central core of moraine that is surrounded by a filter, a transition layer and a fill material. Ideally the seepage through the dam is relatively small and the effect on the dam from the flow is negligible. However, in reality there are several situations that promote a fatal failure of the dam including overtopping at high flood discharges, internal erosion and seepage problems in the embankment and the foundation. The status of embankment dams are generally examined by in-situ measurement of one or several of the following quantities: pore pressure, inclination and settlement, temperature, resistivity, self-potential, seepage rate, turbidity of the seepage water, ground penetration radar and bore hole tomography. These indirect and/or discrete methods give indication of the condition of the dam leaving the real situation for the imagination. Hence, when there are alterations to measured values great efforts are often spent on reinforcing dams in order to keep a high safety level. An increased knowledge of the composition of material in dams would enable the usage of focused measures reducing the costs and increasing the safety.

  • 161.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Granström, Reine
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    PIV analysis of merging flow in a simplified model of a rotary kiln2012Conference paper (Refereed)
  • 162.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Granström, Reine
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    PIV analysis of merging flow in a simplified model of a rotary kiln2012In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 53, no 2, p. 545-560Article in journal (Refereed)
    Abstract [en]

    Rotary kilns are used in a variety of industrial applications. The focus in this work is on characterizing the non-reacting, isothermal flow field in a rotary kiln used for iron ore pelletization. A downscaled, simplified model of the kiln is experimentally investigated using particle image velocimetry. Five different momentum flux ratios of the two inlet ducts to the kiln are investigated in order to evaluate its effect on the flow field in general and the recirculation zone in particular. Time-averaged and phase-averaged analyses are reported, and it is found that the flow field resembles that of two parallel merging jets, with the same characteristic flow zones. The back plate separating the inlet ducts acts as a bluff body to the flow and creates a region of reversed flow behind it. Due to the semicircular cross-section of the jets, the wake is elongated along the walls. Conclusions are that the flow field shows a dependence on momentum flux ratio of the jets; as the momentum flux ratio approaches unity, there is an increasing presence of von Kármán-type coherent structures with a Strouhal number of between 0.16 and 0.18. These large-scale structures enhance the mixing of the jets and also affect the size of the recirculation zone. It is also shown that the inclination of the upper inlet duct leads to a decrease in length of the recirculation zone in certain cases.

  • 163.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Johansson, Simon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    PIV/PLIF experiments of jet mixing in a model of a rotary kiln2015In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 56, no 5, article id 111Article in journal (Refereed)
  • 164. Larsson, Sofia
    et al.
    Lindmark, Elianne
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    Töyrä, Simon
    LKAB.
    Kiln aerodynamics: visualisation of merging flow by usage of PIV and CFD2009In: Proceedings from Seventh International Conference on Computational Fluid Dynamics in Minerals and Process Industries: CSIRO, Melbourne, Australia, 2009Conference paper (Refereed)
    Abstract [en]

    One way to upgrade iron ore is to process it into pellets. Such a process includes several stages involving complex fluid dynamics. In this work the focus is on the grate-kiln pelletizing process and especially on the rotary kiln, with the objective to get a deeper understanding of itsthe aerodynamics. A down-scaled, simplified model of a full-scale kiln is created and both a numerical and an experimental analysis of the flow field are performed. Conclusions are that steady state simulations can be used to get an overview over the main features of the flow field. Precautions should though be taken when analysing the recirculation zone since the steady state simulations do not capture the transient, oscillating behaviour of the flow seen in the validation experiments, which affects the size of the recirculation zone.

  • 165. Larsson, Sofia
    et al.
    Lindmark, Elianne
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    Töyrä, Simon
    LKAB.
    Visualization of merging flow by usage of PIV and CFD with application to grate-kiln induration machines2012In: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 5, no 4, p. 81-89Article in journal (Refereed)
    Abstract [en]

    One way to upgrade iron ore is to process it into pellets. Such a process includes several stages involving complex fluid dynamics. In this work, focus is on the grate-kiln pelletizing process and especially on the rotary kiln, with the objective to get a deeper understanding of the aerodynamics in order to improve the combustion. A down-scaled, simplified model of the real kiln is created and both numerical and experimental analyses of the flow field are performed. Conclusions are that steady state simulations can be used to get an overview over the main features of the flow field. Precautions should though be taken when analyzing the recirculation zone since steady state simulations do not capture the transient, oscillating behavior of the flow seen in the physical experiment. These oscillations will under certain conditions considerably affect the size of the recirculation zone.

  • 166.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lindmark, Elianne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nathan, Graham
    University of Adelaide.
    Secondary flow in semi-circular ducts2011In: Proceedings of the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics / [ed] J.P. Meyer, 2011, p. 725-732Conference paper (Refereed)
  • 167.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lindmark, Elianne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nathan, Graham
    University of Adelaide.
    Secondary flow in semi-circular ducts2011In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 133, no 10, article id 101206Article in journal (Refereed)
    Abstract [en]

    Turbulent secondary flows are motions in the transverse plane, perpendicular to a main, axial flow. They are encountered in non-circular ducts and can, although the velocity is only of the order of 1–3% of the streamwise bulk velocity, affect the characteristics of the mean flow and the turbulent structure. In this work, the focus is on secondary flow in semi-circular ducts which has previously not been reported. Both numerical and experimental analyses are carried out with high accuracy. It is found that the secondary flow in semi-circular ducts consists of two pairs of counter rotating corner vortices, with a velocity in the range reported previously for related configurations. Agreement between simulation and experimental results are excellent when using a second moment closure turbulence model, and when taking the experimental and numerical uncertainty into account. New and unique results of the secondary flow in semi-circular ducts have been derived from verified simulations and validating laser-based experiments.

  • 168. Larsson, Sofia
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Kilnaerodynamik2009In: Svenska mekanikdagarna: Södertälje 2009, Stockholm: Svenska nationalkommittén för mekanik , 2009, p. 105-Conference paper (Other academic)
  • 169.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lycksam, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Tomographic PIV of flow through ordered thin porous media2018In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 59, no 6, article id 96Article in journal (Refereed)
    Abstract [en]

    Pressure-driven flow in a model of a thin porous medium is investigated using tomographic particle image velocimetry. The solid parts of the porous medium have the shape of vertical cylinders placed on equal interspatial distance from each other. The array of cylinders is confined between two parallel plates, meaning that the permeability is a function of the diameter and height of the cylinders, as well as their interspatial distance. Refractive index matching is applied to enable measurements without optical distortion and a dummy cell is used for the calibration of the measurements. The results reveal that the averaged flow field changes substantially as Reynolds number increases, and that the wakes formed downstream the cylinders contain complex, three-dimensional vortex structures hard to visualize with only planar measurements. An interesting observation is that the time-averaged velocity maximum changes position as Reynolds number increases. For low Reynolds number flow, the maximum is in the middle of the channel, while, for the higher Reynolds numbers investigated, two maxima appear closer to each bounding lower and upper wall.

  • 170.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Turbulent sekundärflöde i semicirkulära kanaler2011Conference paper (Refereed)
  • 171.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    Calculation of Kiln Aerodynamics with two RANS turbulence models and by DDES2015In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 94, no 4, p. 859-878Article in journal (Refereed)
    Abstract [en]

    Rotary kilns are large, cylindrical, rotating ovens with a burner in one end that are used in various industrial processes to heat up materials to high temperatures. The kiln burners are characterized by long diffusion flames where the combustion process is largely controlled by the turbulent diffusion mixing between the burner fuel jet and the surrounding combustion air. The combustion air flow patterns have a significant effect on the mixing and hence the combustion efficiency, motivating a systematic study of the kiln aerodynamics. The objective of this work is to compare turbulence models when modeling the kiln aerodynamics of an iron ore pelletizing rotary kiln. Simulations of the non-reacting isothermal flow using three different ω-based turbulence models are performed on a simplified, down-scaled model of the kiln. Some of the results are validated against particle image velocimetry (PIV) experiments. The turbulence models used are the two-equation shear stress transport (SST) model, the Reynolds stress baseline (RSM-BSL) model and the delayed detached eddy simulation (DDES) turbulence model based on the SST formulation. It is found that the turbulence models produce quite different results yielding various predictions of the flow field. The SST model fails to capture the unsteady behavior of the flow field and the DDES model performs poorly on the grid applied. The Reynolds stress model agrees best when compared with the experimental data and provides a good trade-off between details captured and computational effort.

  • 172.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    Comparison of three turbulence models in the modeling of kiln aerodynamics2014Conference paper (Refereed)
  • 173.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    The Flow Field in a Virtual Model of a Rotary Kiln as a Function of Inlet Geometry and Momentum Flux Ratio2015In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 137, no 10, article id 101102Article in journal (Refereed)
    Abstract [en]

    The rotary kiln is the middle part of a grate-kiln iron ore pelletizing process and consists of a large, cylindrical rotating oven with a burner in one end. The flame is the heart of the process, delivering the necessary heat. The combustion process is largely controlled by the turbulent diffusion mixing between the primary fuel jet and the combustion air, called the secondary air, which is mostly induced through the kiln hood. The relatively high momentum of the secondary air implies that the resulting flow field has a significant impact on the combustion process, justifying a systematic study of the factors influencing the dynamics of the secondary air flow field, by neglecting the primary fuel jet and the combustion. The objective of this work is thus to investigate how the geometry and the momentum flux ratio of the inlets affect the flow field in the kiln. Down-scaled models of the kiln are investigated numerically. It is found that the resulting flow field is highly affected by both the geometry and momentum flux ratio of the inlet flows, including effects from pressure driven secondary flow occurring in the semicircular inlet ducts. The dynamics of the flow is further investigated using proper orthogonal decomposition (POD) resulting in a deeper understanding of the forming, interaction and convection of the vortical structures

  • 174.
    Larsson, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Simulation of the flow field in an iron ore pelletizing kiln2016In: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 33, no 3, p. 144-148Article in journal (Refereed)
    Abstract [en]

    The flow field in a rotary kiln, used in an iron ore pelletizing process, was investigated using a three-dimensional computational fluid dynamics model. The model is isothermal, downscaled and simplified. The objective was to examine the possibility of capturing the unsteady motion of the flame seen in the real kiln. The results from the simulations were compared with recorded images of the real process. The results demonstrate the possibility of quickly getting an overview of the flow field in the kiln. The main, unsteady behavior of the flame was captured. The model may be used as a tool in the ongoing work of improving and optimizing the pelletizing process.

  • 175.
    Li, Jinxia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Green, Torbjörn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Baart, Pieter
    µPIV measurement of grease velocity profiles in channels with two different types of flow restrictions2012In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 54, p. 94-99Article in journal (Refereed)
    Abstract [en]

    Grease is commonly used to lubricate various machine components such as rolling bearings and seals. In this paper the flow of lubricating grease passing restrictions is described. Such flow occurs in rolling bearings during relubrication events where the grease is flowing in the transverse (axial) direction through the bearing and is hindered by guide rings, flanges et cetera, as well as in seals where transverse flow occurs, for example during so-called breathing caused by temperature fluctuations in the bearing. This study uses a 2D flow model geometry consisting of a wide channel with rectangular cross-section and two different types of restrictions to measure the grease velocity vector field, using the method of Micro Particle Image Velocimetry. In the case of a single restriction, the horizontal distance required for the velocity profile to fully develop is approximately the same as the height of the channel. In the corner before and after the restriction, the velocities are very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving. This condition particularly applies to the cases with a low-pressure drop and where high consistency grease is used. In practice this means that grease is not replaced in such “corners” and that some aged/contaminated grease will remain in seal pockets.

  • 176.
    Li, Jinxia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Green, Torbjörn
    Lundström, Staffan
    Lugt, Piet
    Baart, Pieter
    Measurements of grease flow in channels with restrictions using μPIV2010In: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Conference paper (Refereed)
    Abstract [en]

    Grease is commonly used to lubricate various machine components such as rolling element bearings, open gears etc. Better understanding of the flow properties of grease will contribute to understanding the lubrication mechanism in bearings and flow in lubrication systems. In an earlier paper Micro Particle Image Velocimetry (μPIV) techniques were used to study the flow in a rectangular channel. The present paper is an extension of this work where restrictions were applied in such a channel, which creates a much more complex velocity field. The grease is seeded with fluorescent particles, which are illuminated by a double-pulsed laser. The test geometries that are used in this study are a channel with one flat restriction and one with two flow restrictions in a similar channel. The stationary grease mass-flow and the two dimensional velocity fields have been monitored for different pressure drops. For the channel with one flat restriction, the flow was measured to be symmetric at the inlet and outlet, and the distance for the flow to fully develop is comparable with the height of the channel; Slow motion was followed near the step corner at the inlet. For the channel with two flow restrictions, the vector profiles show that the maximum velocity appears at the restrictions; In-between the two restrictions, a part of the grease is not moving. This particularly applies to cases with low-pressure drop and where high consistency grease was used.

  • 177.
    Li, Jinxia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Design of test rig for visualizations of cylindrical shear and pressure driven Couette flow using μPIV2014Conference paper (Refereed)
    Abstract [en]

    Couette flow is often encountered in concentric cylinder application such as rheometers etc. Being able to visualize such flows is of interest both from a fundamental point of view to understand the dynamics of complex fluids, but also in specific applications such as lubricants flowing through seal geometries. In this study a concentric cylinder test rig has been designed to visualize Couette flow in both radial and axial direction using micro Particle Image Velocimetry. The rig allows for control of the flow motion; the rotating inner cylinder creates a peripheral flow and an applied pressure in the axial direction creates a pressure driven flow. Thus, a single flow direction or a combination of directions can be analyzed. To demonstrate the technique a flow of a non-Newtonian shear thinning fluid in the form of lubricating grease was investigated and discussed. It is found that it is possible to capture the yield behavior of the grease, with regions of fully and partially yielded flow visible. The influence of temperature creep flow is also presented. Grease with both high and low yield stress are measured and compared could be measured and compared in a pocket with variable size. Furthermore, non-homogeneous effects such as shear banding and wall slip can be visualized. The test rig has thus a high potential to investigate the influence of wall material and wettability between fluids and the housing on the flow and wall slip behavior as long as the fluid is optically transparent.

  • 178.
    Li, Jinxia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Grease free surface flow on a rotating plate2014Conference paper (Refereed)
    Abstract [en]

    In order to improve the understanding of grease flow in various applications such as gears, seals and rolling element bearings, free surface flow of different greases under different running conditions has been investigated. A rotating disc has been used to study grease flow as the grease is subjected to a centrifugal force. The adhesion and mass loss was detected for greases with different rheology on different surfaces and surface textures. It is shown that the speed at which grease starts to move is mostly determined by grease type, yield stress and bleeding properties rather than surface material. Also, the surface adhesion is shown to be influenced both by the rheology of the grease and the surface material.

  • 179.
    Li, Jinxia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Baart, Pieter
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Lubricating grease shear flow and boundary layers in a concentric cylinder configuration2013In: Proceedings of the 3rd International Tribology Symposium of IFoMM (International Federation for the Promotion of Mechanism and Machine Science), Luleå, March 19-21, 2013, 2013Conference paper (Refereed)
    Abstract [en]

    Grease is extensively used to lubricate various machine elements such as rollingbearings, seals, and gears. Understanding the flow dynamics of grease is relevant forthe prediction of the grease distribution for optimum lubrication and the migration ofwear- and contaminant particles. In this study grease flow is visualized using themethod of micro Particle Image Velocimetry; the experimental setup comprises aconcentric cylinder with rotating shaft to simulate the grease flow in a DoubleRestriction Seal (DRS) geometry with two different grease pocket heights. It is shownthat grease may be partially yielded in the large grease pocket geometry and fullyyielded in the small grease pocket geometry. For the small grease pocket geometry, itis shown that three distinct grease flow layers are present: a high shear rate regionclose to the stationary wall, a bulk flow layer, and a high shear rate boundary regionnear the rotating shaft. The grease shear thinning behaviour and its wall slip effectshave been detected and discussed.

  • 180.
    Lindberg, Dan-Erik
    et al.
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Studies.
    Leonardsson, Kjell
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Studies.
    Andersson, Anders G.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundqvist, Hans
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Studies.
    Methods for locating the proper position of a planned fishway entrance near a hydropower tailrace2013In: Limnologica, ISSN 0075-9511, E-ISSN 1873-5851, Vol. 43, no 5, p. 339-347Article in journal (Refereed)
    Abstract [en]

    The spatial distribution of upstream migrating Atlantic salmon (Salmo salar) spawners was studied in 2008 and 2009 in the surroundings of the tailrace from a hydropower station in the River Umeälven. This area is problematic because the fish have difficulties finding their way into the original riverbed, which prompted an investigation on the feasibility of adding a fishway in the area. Echo sounding was used in 2008 to investigate the spatial use of fish in the tailrace channel during the time of salmon migration. Presence of other fish species was so low that all echo sounding detections were assumed to be salmon. In 2009, data on wild radio-tagged salmon (n = 94) was collected in the same tailrace by an array of underwater antennas with a detection radius of approximately 10 m, to validate the results from the echo sounding. Both types of surveys showed aggregations of fish in one part of the tailrace. As a final step, Computational Fluid Dynamics (CFD) modeling was performed to analyze hydrodynamics. This CFD modeling showed a coincidence of fish detections in areas with turbulence intensities between 0.6 and 0.8, which may be an indication that the fish are holding in these areas to reduce energy expenditure during migration. A high proportion of the radio-tagged salmon were observed in the tailrace area (a median of 21 days between their first and last detection), indicating that the salmon are delayed in their upstream migration by the attraction to the tailrace in this area. The overall data on fish behavior in the tailrace led us to suggest a location for a new fishway where the fish aggregation was most pronounced. The number of detections from either technology had similar distributions over the tailrace, suggesting that the results are comparable. Thus, the split beam echo sounder can preferably be used to investigate which location is most appropriate for locations of entrances to new fishways since many more individual fishes are covered by this method compared to telemetry. Furthermore, there is no need to handle the fish in the echo sounding studies as is required in telemetry studies

  • 181.
    Lindgren, M.
    et al.
    Luleå tekniska universitet.
    Marjavaara, Daniel
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Automatic design of hydropower flows: the draft tube2002In: Computational technologies for fluid/thermal/structural/chemical systems with industrial applications: presented at the [International Symposium on Computational Technologies for Fluid/Thermal/Chemical/Stress Systems with Industrial Applications], 2002 ASME Pressure Vessels and Piping Conference, Vancouver, British Columbia, Canada, August 5 - 9, 2002 / [ed] C.R. Kleijn, New York: American Society of Mechanical Engineers, Pressure Vessels and Piping Division , 2002, Vol. 448, No. 1, p. 299-307Conference paper (Refereed)
    Abstract [en]

    The focus is set on a redesign of an existing draft tube by usage of an automated optimisation based on CFD calculations. By this method a design can be predicted in terms of a predefined objective function, here the pressure recovery factor. The design parameters used are based on spline-functions that are set under certain restrictions. One is that the new design should fit into the old one. The optimisation is performed with the Response Surface Method (RSM) implemented on the commercial code iSIGHT6.0. The flow simulations are carried out with the commercial code, CFX4, with the standard k-ε turbulence model and with boundary conditions based on detailed experimental data. With this set-up and the chosen parameterisation the highest value is found at the edge of the design space allowing for further improvements.

  • 182. Lindmark, Elianne
    et al.
    Green, Torbjörn
    Gustavsson, Håkan
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Increasing the attraction water velocity at fishway entrances: model and field experiments2008In: Proceedings of the 19th International Symposium on Transport Phenomena (ISTP-19): Reykjavik, Iceland, August 17-21, 2008 / [ed] Sigurdur Brynjolfsson; Olafur Petur Palsson; Jong H. Kim, University of Iceland, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science , 2008Conference paper (Refereed)
    Abstract [en]

    When Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) migrates upstream rivers they encounter obstructions such as hydropower plants. To increase the water velocity at the fish inlet of a fishway an attraction channel is used. The channel increases the velocity without using extra attraction water from the reservoir. Field experiments show that fish use the channel, and lab experiments show that the water velocity out of the channel is 38 % higher than the surrounding velocity and the increased velocity lasts for about 18 water depths down stream.

  • 183.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andersson, Robin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andersson, Anders G.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Eriksson, Mats
    Relitor Engineering AB.
    Modelling the Evaporation Rate in an Impingement Jet Dryer with Multiple Nozzles2017In: International Journal of Chemical Engineering, ISSN 1687-806X, E-ISSN 1687-8078, Vol. 2017, article id 5784627Article in journal (Refereed)
    Abstract [en]

    Impinging jets are often used in industry to dry, cool, or heat items. In this work, a two-dimensional Computational Fluid Dynamics model is created to model an impingement jet dryer with a total of 9 pairs of nozzles that dries sheets of metal. Different methods to model the evaporation rate are studied, as well as the influence of recirculating the outlet air. For the studied conditions, the simulations show that the difference in evaporation rate between single- and two-component treatment of moist air is only around 5%, hence indicating that drying can be predicted with a simplified model where vapor is included as a nonreacting scalar. Furthermore, the humidity of the inlet air, as determined from the degree of recirculating outlet air, has a strong effect on the water evaporation rate. Results show that the metal sheet is dry at the exit if 85% of the air is recirculated, while approximately only 60% of the water has evaporated at a recirculation of 92,5%

  • 184.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Frishfelds, Vilnis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Endimensionell bäddmodell för simulering av torkning av järnmalmspellets2011Conference paper (Refereed)
    Abstract [sv]

    Järnmalmspellets är en högt förädlad produkt utvecklad av gruvindustrin för användning iexempelvis masugnar. För ett bandugnsverk sker pelletsprocessen huvudsakligen i fyra steg då en kontinuerlig bädd av pellets transporteras på rosterband genom torkzon, förvärmningzon,brännzon och kylzon. Genomströmmande luft används för att torka, sintra och kyla materialet ide olika zonerna. Då produktionen av järnmalmspellets är tids- och energikrävande finns deten naturlig drivkraft att förbättra processen så att produktionen kan optimeras medbibehållen produktkvalitet.För att i detalj studera torkzonen har en modell för konvektiv torkning av en enskildpellet tidigare tagits fram. Resultat från simuleringarna visar tydligt fyra torkningsfaser; i)förångning av vätska från pelletens yta, ii) förångning av vätska vid ytan samtidigt som vissinre förångning sker då ytan lokalt är torr, iii) torkning enbart på grund av inre förångningoch iv) kokning av vatten inuti pelleten [1]. Den framtagna torkningsmodellen har ävenapplicerats på en sfärisk geometri med syfte att undersöka hur fukthalten i inloppsluftenpåverkar torkningen [2]. Simuleringar visar att effekten av luftfuktighet främst uppkommeri början av den första torkningsfasen medan skillnaderna minskar i slutet av perioden då ettförlängt stadie av konstant torkhastighet fås vid höga luftfuktigheter.Ovanstående resultat visar att det är av stort intresse att även undersöka hur pellets i enpelletbädd påverkas av omgivande lufttemperatur och luftfuktighet. En endimensionellbäddmodell har därför utvecklats som ett komplement till enkulemodellen för attundersöka hur våttemperatur, pellettemperatur, torkhastighet etc. varierar som funktion avbäddhöjd i den första torkningsfasen. I modellen beräknas förångning från pelletsens ytamed motsvarande fukttransport genom den porösa bädden och det är därmed möjligt attutreda vilka områden i bädden som påverkas av eventuell återkondensation.

  • 185.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Frishfelds, Vilnis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    Discrete and continuous modelling of heat and mass transport in drying of a bed of iron ore pellets2012In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 30, no 7, p. 760-773Article in journal (Refereed)
    Abstract [en]

    Drying of a porous bed of iron ore pellets is here considered by modeling a discrete two-dimensional system of round pellets. As a complement to the two-dimensional model, a continuous one-dimensional model enabling fast calculations is developed. Results from the discrete model show that the temperature front advances faster in areas with large distances between the pellets. In areas with low flow speed, the temperature of the pellets increases with a relatively slow rate. The water inside these pellets will therefore remain for a long time. The continuous model fits the discrete model very well for a regular distribution of equal-sized particles. A discrete model with irregular packing will, compared to the continuous model, show a larger variation in the distribution of temperature and moisture content in the final phase of drying.

  • 186.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lindmark, Elianne M.
    AB Electrolux.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Influence of plate size on the evaporation rate of a heated droplet2015In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 33, no 15-16, p. 1963-1970Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to numerically investigate how the width of a plate influences natural convection around a droplet. Droplets evaporating on hot surfaces has many applications including drying of dishes and paint. Evaporation rate and deposition of particles withheld in the fluid is of great importance in both cases. As a first step to investigate how the drying rate and deposition mechanisms can be controlled, this work aims to investigate how the external flow around a water droplet influences the evaporation rate. Natural convection caused by the hot plate on which the droplet rests is considered and the effect of different widths is examined. Results show that an extension of the plate past the droplet will increase the maximum velocity in the domain due to natural convection while the flow close to the surface is decreased due to the no slip condition and temperature gradient. A decrease of the evaporation rate is therefore observed when the plate is extended past the droplet as compared to the case when the plate and droplet have the same diameter. Simulations furthermore show that the results from the heat and mass transfer analogy only compare well to the results of Fick's law when the droplet and plate has the same width.

  • 187.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lindmark, Elianne M.
    AB Electrolux.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Influence of plate size on the evaporation rate of a heated droplet2014Conference paper (Refereed)
    Abstract [en]

    Droplets evaporating on hot surfaces has many applications including drying of dishes and paint. Evaporation rate and deposition of particles withheld in the fluid is of great importance in both cases. As a first step to investigate how the drying rate and deposition mechanisms can be controlled, this work aims to investigate how the external flow around a droplet influences the evaporation rate. Natural convection of the surrounding fluid caused by heated plates of different widths is considered and the effect of the heat and mass transfer mechanisms on the evaporation rate is investigated.

  • 188.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Heat and mass transfer boundary conditions at the surface of a heated sessile droplet2017In: Heat and Mass Transfer, ISSN 0947-7411, E-ISSN 1432-1181, Vol. 53, no 12, p. 3581-3591Article in journal (Refereed)
    Abstract [en]

    This work numerically investigates how the boundary conditions of a heated sessile water droplet should be defined in order to include effects of both ambient and internal flow. Significance of water vapor, Marangoni convection, separate simulations of the external and internal flow, and influence of contact angle throughout drying is studied. The quasi-steady simulations are carried out with Computational Fluid Dynamics and conduction, natural convection and Marangoni convection are accounted for inside the droplet. For the studied conditions, a noticeable effect of buoyancy due to evaporation is observed. Hence, the inclusion of moisture increases the maximum velocities in the external flow. Marangoni convection will, in its turn, increase the velocity within the droplet with up to three orders of magnitude. Results furthermore show that the internal and ambient flow can be simulated separately for the conditions studied, and the accuracy is improved if the internal temperature gradient is low, e.g. if Marangoni convection is present. Simultaneous simulations of the domains are however preferred at high plate temperatures if both internal and external flows are dominated by buoyancy and natural convection. The importance of a spatially resolved heat and mass transfer boundary condition is, in its turn, increased if the internal velocity is small or if there is a large variation of the transfer coefficients at the surface. Finally, the results indicate that when the internal convective heat transport is small, a rather constant evaporation rate may be obtained throughout the drying at certain conditions.

  • 189. Ljung, Anna-Lena
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Strömningsmekaniken för torkning av järnmalmspellets2007In: Svenska Mekanikdagar 2007: Program och abstracts / [ed] Niklas Davidsson; Elianne Wassvik, Luleå: Luleå tekniska universitet, 2007, p. 80-Conference paper (Other academic)
  • 190.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Sjöström, Ulf
    Swerea MEFOS AB.
    Marjavaara, Daniel
    LKAB.
    Lindblom, Bo
    LKAB.
    Tano, Kent
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Drying of an iron ore pellet: investigation of the influence of surface irregularities and overall geometry2010In: Proceedings of the 3rd International Conference on Porous Media and its Applications in Science and Engineering, ICPM3, 2010Conference paper (Refereed)
    Abstract [en]

    In this paper, simulations of the first drying period of a single iron ore pellet are compared for: i) a scanned pellet from experiments ii) an oval pellet resembling the experimental one with equivalent volume iii) a spherical pellet with equivalent volume. The comparison provides information on how simplifications of an actual geometry might affect the result. The simulations are carried out with the commercial software ANSYS CFX 12.0 and the model is validated against experimental results with good agreement. The results show that the local moisture content at the surface is influenced by both surface irregularities and overall geometry. A smooth surface will decrease the local variation of moisture while a spherical geometry will, compared to an oval, increase the difference.

  • 191.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan T.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Evaporation of a sessile water droplet subjected to forced convection in humid environment2019In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 37, no 1, p. 129-138Article in journal (Refereed)
    Abstract [en]

    The evaporation of a sessile droplet is here investigated numerically with a design of experiment approach. Boundary conditions are chosen based on forced convection in humid air, i.e., mimicking the conditions inside a dishwasher. Computational fluid dynamic simulations of an axisymmetrical droplet placed on a heated plate show that relative humidity, initial contact angle, plate temperature, and temperature difference between plate and air all have significant effect on the initial evaporation rate. For the studied conditions, relative humidity is the most significant factor while the magnitude of the velocity and type of internal flow are insignificant within a 95% confidence interval.

  • 192.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Tano, Kent
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Enkulemodell för torkning av järnmalmspellets2009In: Svenska mekanikdagarna: Södertälje 2009, Stockholm: Svenska nationalkommittén för mekanik , 2009, p. 104-Conference paper (Other academic)
  • 193.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Tano, Kent
    Fluid flow and heat transfer within and around a porous iron ore pellet placed in infinite space2008In: Proceedings of the 19th International Symposium on Transport Phenomena (ISTP-19): Reykjavik, Iceland, August 17-21, 2008 / [ed] Sigurdur Brynjolfsson; Olafur Petur Palsson; Jong H. Kim, University of Iceland, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science , 2008Conference paper (Refereed)
    Abstract [en]

    The forced convective heating of a porous cylinder with properties similar to an iron ore pellet is here numerically investigated. The numerical setup is based on a two dimensional microporous model with surrounding flow field taken into account. The simulations are carried out with special attention directed towards minimizing numerical errors. With interface conditions provided by CFD, simulations show an increased heat transfer rate for the porous cylinder when compared to a solid.

  • 194.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Tano, Kent
    LKAB.
    Heat and mass transfer in a single iron ore pellet during drying2009In: Proceedings of 4th ICAPM: August 10-12, 2009, Istanbul, Turkey, 2009Conference paper (Refereed)
  • 195.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Tano, Kent
    Heat, mass and momentum transfer within an iron ore pellet during drying2008In: Proceedings of CHT-08 ICHMT International Symposium on Advances in Computational Heat Transfer, International Centre for Heat and Mass Transfer , 2008Conference paper (Refereed)
    Abstract [en]

    Iron ore pellets is one of the most refined products for mining industry. Being such, there is a natural driving force to enhance the pelletization in order to optimize production and improve quality especially since the process is time and energy consuming. In order to be successful it is of highest importance that the pelletization process is known in detail. Following this demand, heat and mass transport within a single pellet during drying is modeled with aid of Computational Fluid Dynamics. A two dimensional rectangular domain is chosen to represent the porous media within the pellet and the governing equations are set up for one directional flow through it. Convective transport of water and air through the capillaries of the porous media is computed from Darcy's law being adapted to a two-fluid system. Vaporization by boiling is taken into account and two energy equations are used to calculate the temperature distribution, one for the liquid and solid, and one for the gas. To start with, iteration errors and discretization errors are found to be negligible. Following this a sensitivity analysis shows that it is important to use a realistic value of the convective heat transfer coefficient when the vaporization of water is the dominating drying mechanism while the temperature of the solid and capillary movement of water is not influenced to the same extent. The derived model can be applied to a number of numerical set-ups such as a single pellet in an infinite space.

  • 196.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Tano, Kent
    Simulation of convective drying of a cylindrical iron ore pellet2011In: International journal of numerical methods for heat & fluid flow, ISSN 0961-5539, E-ISSN 1758-6585, Vol. 21, no 6, p. 703-716Article in journal (Refereed)
    Abstract [en]

    Purpose – The purpose of this paper is to numerically model convective drying of a two-dimensional iron ore pellet subjected to turbulent flow.Design/methodology/approach – Simulations of the iron ore pellet drying process are carried out with commercial computational fluid dynamics software. The moisture distribution inside the pellet is calculated from a diffusion equation and drying due to evaporation at the surface is taken into account.Findings – The results show an initial warm up phase with a succeeding constant rate drying period. Constant drying rate will only be achieved if the surface temperature is constant. The falling rate period will subsequently start at the forward stagnation point when the minimum moisture content is reached, while other parts of the surface still provide enough moisture to allow surface evaporation. The phases will thus coexist for a period of time.Research limitations/implications – Owing to the complex physical processes involved in iron ore pellet drying, some parameters in the model are based on estimations. The effective diffusivity should, for example, in the future be investigated more thoroughly. It is also important to extend the model so that the falling rate drying period is also included. The model is at present undergoing further validation.Practical implications – The simulations can provide detailed information on some key fluid dynamics and physical processes that an iron ore pellet undergoes during drying.Originality/value – The simulations enhance the understanding of iron ore pellet drying and the model provides a complement to experimental investigations when optimizing the drying process.

  • 197.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Tano, Kent
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Simulation of heat transfer and fluid flow in a porous bed of iron ore pellets during up-draught drying2006In: Proceedings of the Fifth International Conference on CFD in the Process Industries: Hilton on the Park, Melbourne, Australia, 13-15 December 2006 / [ed] P.J. Witt, Melbourn: CSIRO Publishing, 2006Conference paper (Refereed)
    Abstract [en]

    Iron ore pellets is one of the most refined products for companies such as LKAB and it is therefore a global need for research in the area in order to optimize the production and improve quality. This work aim at modelling and optimizing the drying zone of a travelling grate pelletizing plant and to start with, a model of velocity and temperature distribution in the up-draught drying zone is developed with aid of computational fluid dynamics. The velocity distribution in the porous bed is described by laws of fluid dynamics in porous media. The dominating heat transfer mechanism is convection and two energy equations are required since the porous media region contains both fluid and solid. Result from simulations show a rapid cooling of air due to the high specific surface area in the porous material. Conclusions are that it is possible to simulate convective heat transfer within a porous media in ANSYS CFX 10.0. There are however some limitations when using the diffusive transport equation as the solid phase energy equation that need further investigation. Moisture content and condensation in the bed are not included in the present model and is therefore subject to future work

  • 198.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Influence of sample temperature on drying of individual porous spheres2011Conference paper (Refereed)
    Abstract [en]

    Heat and mass transport within a porous sphere during drying is here modeled and simulations of the surface evaporation period are carried out with aim to investigate the influence of the initial temperature on the drying time. A three dimensional spherical domain is formed and governing equations are set up for the flow past it. The local heat and mass transfer at the surface is determined from simulations of the surrounding fluid flow with aid of Computational Fluid Dynamics. For the studied conditions, the results show that increasing the initial temperature will decrease the drying time in a rather linear manner. There is also a distinct reduction in drying time if the humidity of the surrounding air is lowered. Increasing the initial temperature could thus be an effective way to reduce problems due to condensation and to decrease the drying time.

  • 199.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Modeling evaporation of droplets on a heated plate2014Conference paper (Refereed)
  • 200.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Numerical study of the heat and mass transfer conditions at the surface of a heated droplet2014Conference paper (Refereed)
    Abstract [en]

    This work aims to numerically investigate how the heat and mass transfer boundary conditions at a droplet surface should be presented in order to fully represent the surrounding fluid flow. With aid of Computational Fluid Dynamics, a numerical study is carried out to investigate the validity of the heat and mass transfer analogy at the droplet surface. Natural convection in the air surrounding the droplet, arising from the heated surface below the droplet, is considered. The heat and mass transfer analogy needs to be deliberated when the evaporation is dominated by density differences rather than temperature differences and the numerical results show this transition in detail.

1234567 151 - 200 of 334
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