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  • 1.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Moreno, Sergio
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vacuum infusion of cellulose nanofibre network composites: Influence of porosity on permeability and impregnation2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 95, p. 204-211Article in journal (Refereed)
    Abstract [en]

    Addressing issues around the processing of cellulose nanofibres (CNF) composites is important in establishing their use as sustainable, renewable polymer reinforcements. Here, CNF networks of different porosity were made with the aim of increasing their permeability and suitability for processing by vacuum infusion (VI). The CNF networks were infused with epoxy using two different strategies. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated. Calculated fill-times for CNF networks with 50% porosity were the shortest, but are only less than the gel-time of the epoxy if capillary effects are included. In experiments the CNF networks were clearly wetted. However low transparency indicated that impregnation was incomplete. The modulus and strength of the dry CNF networks increased rapidly with decreasing porosity, but their nanocomposites did not follow this trend, showing instead similar mechanical properties to each other. The results demonstrated that increasing the porosity of the CNF networks to ≈ 50% gives better impregnation resulting in a lower ultimate strength, a higher yield strength and no loss in modulus. Better use of the flow channels in the inherently layered CNF networks could potentially reduce void content in these nanocomposites and thus increase their mechanical properties.

  • 2.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Moreno, Sergio
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vacuum Infusion of Nanocellulose Networks of Different Porosity2015In: 20th International Conference on Composite Materials: Copenhagen, 19-24th July 2015, ICCM , 2015, article id 4109-1Conference paper (Refereed)
    Abstract [en]

    Cellulose nanofibres (CNF) have shown good potential as sustainable, biobased reinforcing materials in polymer composites. Addressing issues around the processing of these composites is an important part of establishing their use in different applications. Here, CNF networks of different porosity are made from nanofibrillated hardwood kraft pulp with the aim of increasing the impregnation of the CNF networks and to allow vacuum infusion to be used. Two different vacuum infusion strategies: in-plane and out of plane were used to infuse the CNF networks with a low viscosity epoxy. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated and compared to a micro-fibre based network. Using the out-of-plane permeability measurements and Darcy’s law, the fill-time was calculated and showed that the CNF network with 40% porosity had the lowest fill-time when an out-of-plane impregnation strategy is used. However this exceeded the gel-time of the epoxy system. In experiments, the resin reached the other side of the network but low transparency indicated that wetting was poor. The dry CNF preforms showed a very strong dependence on the porosity with both modulus and strength increasing rapidly at low porosity. Interestingly, the composite based on the 60% porosity network showed good wetting particularly with the in-plane infusion strategy, exhibiting a much more brittle fracture and a high yield strength. This shows that in CNF composites produced by VI, lowering the fibre volume content of the CNF composites gives better impregnation resulting in a lower ultimate strength but higher yield strength and no loss in modulus.

  • 3.
    Almqvist, Andreas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Fabricius, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Wall, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Flow in thin domains with a microstructure: Lubrication and thin porous media2017In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1798, article id 020172Article in journal (Refereed)
    Abstract [en]

    This paper is devoted to homogenization of different models of flow in thin domains with a microstructure. The focus is on applications connected to the effect of surface roughness in full film lubrication, but a parallel to flow in thin porous media is also discussed. Mathematical models of such flows naturally include two small parameters. One is connected to the fluid film thickness and the other to the microstructure. The corresponding asymptotic analysis is a delicate problem, since the result depends on how fast the two small parameters tend to zero relative to each other. We give a review of the current status in this area and point out some future challenges.

  • 4.
    Altorkmany, Lobna
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Kharseh, Mohamad
    Civil Environmental Engineering Department, Chalmers University of Technology, Sweden.
    Ljung, Anna-Lena
    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.
    Effect of Working Parameters of the Plate Heat Exchanger on the Thermal Performance of the Anti-Bact Heat Exchanger System to Disinfect Legionella in Hot Water Systems2018In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 141, p. 435-443Article in journal (Refereed)
    Abstract [en]

    The objective of the current study is to analyze the effect of different working parameters on the thermal performance of the Anti-Bact Heat Exchanger system (ABHE). The ABHE system is inspired by nature and implemented to achieve continuous disinfection of Legionella in different human-made water systems at any desired disinfection temperature. In the ABHE system, most of the energy is recovered using an efficient plate heat exchanger (PHE). A model by Engineering Equation Solver (EES) is set-up to figure out the effect of different working parameters on the thermal performance of the ABHE system. The study shows that higher supplied water temperature can enhance the regeneration ratio (RR), but it requires a large PHE area and pumping power (PP) which consequently increase the cost of the ABHE system. However, elevate temperature in use results in a reduced PHE area and PP, which accordingly reduce the cost of the ABHE system. On the other hand, the EES-based model is used to study the effect of the length and the width of the plates used in the PHE on the RR and the required area of the PHE. Finally, taking into account the geometrical parameters, flow arrangement and the initial operating conditions of the PHE, the EES-based model is used to optimize the PHE in which its area is minimized, and the RR of the ABHE system is maximized.

  • 5.
    Altorkmany, Lobna
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Kharseh, Mohamad
    Civil Environmental Engineering Department, Chalmers University of Technology.
    Ljung, Anna-Lena
    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.
    Experimental and Simulation Validation of ABHE for Disinfection of Legionella in Hot Water Systems2017In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 116, p. 253-265Article in journal (Refereed)
    Abstract [en]

    The work refers to an innovative system inspired by nature that mimics the thermoregulation system that exists in animals. This method, which is called Anti Bacteria Heat Exchanger (ABHE), is proposed to achieve continuous thermal disinfection of bacteria in hot water systems with high energy efficiency. In particular, this study aims to demonstrate the opportunity to gain energy by means of recovering heat over a plate heat exchanger. Firstly, the thermodynamics of the ABHE is clarified to define the ABHE specification. Secondly, a first prototype of an ABHE is built with a specific configuration based on simplicity regarding design and construction. Thirdly, an experimental test is carried out. Finally, a computer model is built to simulate the ABHE system and the experimental data is used to validate the model. The experimental results indicate that the performance of the ABHE system is strongly dependent on the flow rate, while the supplied temperature has less effect. Experimental and simulation data show a large potential for saving energy of this thermal disinfection method by recovering heat. To exemplify, when supplying water at a flow rate of 5 kg/min and at a temperature of 50 °C, the heat recovery is about 1.5 kW while the required pumping power is 1 W. This means that the pressure drop is very small compared to the energy recovered and consequently high saving in total cost is promising.

  • 6.
    Andersson, Anders G.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andreasson, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hellström, J. Gunnar I.
    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.
    Modelling and validation of flow over a wall with large surface roughness2012Conference paper (Refereed)
  • 7.
    Andersson, Anders G.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andreasson, Patrik
    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.
    CFD-modelling and validation of free surface flow during spilling of reservoir in down-scale model2013In: Engineering Applications of Computational Fluid Mechanics, ISSN 1994-2060, E-ISSN 1997-003X, Vol. 7, no 1, p. 159-167Article in journal (Refereed)
  • 8.
    Andersson, Anders G.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andreasson, Patrik
    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.
    Modellering av avbördning med fri vattenyta och validering i en skalmodell2011Conference paper (Refereed)
  • 9.
    Andersson, Anders G.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hellström, J. Gunnar I.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andreasson, Patrik
    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.
    Effect of spatial resolution of rough surfaces on numerically computed flow fields with application to hydraulic engineering2014In: Engineering Applications of Computational Fluid Mechanics, ISSN 1994-2060, E-ISSN 1997-003X, Vol. 8, no 3, p. 373-381Article in journal (Refereed)
    Abstract [en]

    In numerical simulations of flow over rough surfaces, the roughness is often not resolved but represented by a numerical model. The validity of such an assumption is investigated in this paper by Reynolds-Averaged Navier-Stokes simulations of flow over a surface with a large roughness. The surface was created from a high-resolution laser scanning of a real rock blasted tunnel. By reducing the geometrical resolution of the roughness in two steps, the importance of an appropriate surface description could be examined. The flow fields obtained were compared to a set-up with a geometrical flat surface where the roughness was represented by a modified form of the Launder and Spalding wall-function. The flow field over the surface with the lowest resolution was substantially different from those of the two finer resolutions and rather close to the results from the set-up with the wall-function. The results also yield that the finer the resolution is the more vorticity is formed close to the rough surface and more turbulence is generated.

  • 10. Andersson, Anders G.
    et al.
    Lindberg, Dan-Erik
    Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies.
    Lindmark, Elianne
    Leonardsson, Kjell
    Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies.
    Andreasson, Patrik
    Lundqvist, Hans
    Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    A numerical study of the location and function of the entrance of a fishway in a regulated river2010In: 8th International Symposium on ECOHYDRAULICS: Bridging between Ecology and Hydraulics and Leading the Society's New Need - Living with Nature, 2010, p. 277-284Conference paper (Refereed)
    Abstract [en]

    Simulation driven design with Computational Fluid Dynamics has been used to evaluate the flow downstream a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations and the tailrace jet from the turbines is stronger in the simulations. The simulations are however considered to capture the important features of the flow in a way that makes them viable for attraction water simulations. A fishway entrance was included in the simulations and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.

  • 11.
    Andersson, Anders G.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lindberg, Dan-Erik
    SLU.
    Lindmark, Elianne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Leonardsson, Kjell
    SLU.
    Andreasson, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundqvist, Hans
    SLU.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    A study of the location of the entrance of a fishway in a regulated river with CFD and ADCP2012In: Modelling and Simulation in Engineering, ISSN 1687-5591, E-ISSN 1687-5605, Vol. 2012, article id 327929Article in journal (Refereed)
    Abstract [en]

    Simulation-driven design with computational fluid dynamics has been used to evaluate the flow downstream of a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed, and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations, and the tailrace jet from the turbines is stronger in the simulations. A fishway entrance was included in the simulations, and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed for further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.

  • 12. Andersson, Anders G.
    et al.
    Lindmark, Elianne
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    CFD-modell av turbinutloppet i Stornorrfors2009In: Svenska mekanikdagarna: Södertälje 2009, Stockholm: Svenska nationalkommittén för mekanik , 2009, p. 106-Conference paper (Other academic)
  • 13.
    Andersson, Anders G.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Kristoffer
    Andreasson, Patrik
    Lundström, Staffan
    Simulation of free surface flow in a spillway with the rigid lid and volume of fluid methods and validation in a scale model2010In: Proceedings, Fifth European Conference on Computational Fluid Dynamics / [ed] Jose C. F. Pereira; Adelia Sequeira; Jose M. C. Pereira, 2010Conference paper (Refereed)
    Abstract [en]

    Simulations on the spilling from a dam were performed and compared to experimental results from a physical scale model. Both mechanical and acoustic methods to measure the velocity were used. The model has three gates leading into the spillway that can be maneuvered separately. At first two of the gates were closed and the inlet flow was high enough to get a fully wetted outlet at the third gate. This case was simulated with a rigid lid approximation since the water surface was considered to be plane. The water surface level was taken from the scale model. In the second case, all three gates were open resulting in a free water surface through all the gates to the spillway. This case was simulated with the Volume of Fluids method were both water and air phase were considered. Water levels, velocities and the shape of the water surface were compared between simulations and experiments. The simulations capture both qualitative features such as a vortex near the outlet and show good quantitative agreement with the experiments.

  • 14. Andersson, Anders G.
    et al.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Papathanasiou, T.D.
    Department of Mechanical Engineering, University of Thessaly.
    Lundström, Staffan
    Flow through a two-scale porosity material2009In: Research Letters in Materials Science, ISSN 1687-6822, E-ISSN 1687-6830, article id 701512Article in journal (Other academic)
    Abstract [en]

    Flow through a two-scale porous medium is here investigated by a unique comparison between simulations performed with computational fluid dynamics and the boundary element method with microparticle image velocimetry in model geometries.

  • 15. Andersson, Anders G.
    et al.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Papathanasiou, Thanasis
    Lundström, Staffan
    Fluid flow through porous media with dual scale porosity2008In: 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]

    Flow in two scale porous media takes place in applications such as advanced composites manufacturing. Knowledge of this flow is of general importance and is crucial for filtration mechanisms when functional filler-particles are added to the liquid resin impregnating the fibrous preform. Means to model and experimentally visualise this flow is here investigated. In particular simulations performed with computational fluid dynamics and the boundary element method are compared to micro particle image velocimetry in a model geometry.

  • 16.
    Andersson, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Leonardsson, Kjell
    Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies.
    Lindberg, Dan-Erik
    Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies.
    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.
    Lundqvist, Hans
    Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies.
    Describing fish passage in a river confluence with telemetry and CFD2016In: / [ed] Webb, JA, Costelloe, JF, CasasMulet, R, Lyon, JP, Stewardson, MJ, Melbourne: University of Melbourne , 2016Conference paper (Refereed)
    Abstract [en]

    The confluence between hydropower tailrace and the old river bed in Stornorrfors in the river Umeälven in the northern part of Sweden has shown to be the largest obstacle for upstream migrating salmon and sea trout during the migrating season. Fish are attracted to the high flow rate from the tailrace and will not migrate upstream in the old river bed being the passage to the fishway leading past the hydropower dam. By triangulating the movements of radio tagged fish using eight antennas in the confluence, it is here possible to describe the individual fish tracks left by radio tagged fish during the migrating season. These tracks are then compared with three-dimensional Computational Fluid Dynamics (CFD) simulations of the confluence. By simulating the most common combinations of turbine flow and spill flow in the old river bed it is then possible to find correlations between individual fish movements and flow parameters such as velocity, turbulence intensity or vorticity for different flow combinations. It was previously assumed that fish had trouble locating the old river bed, the results of the triangulation however shows that most fish finds the old river bed within a few days but does not chose to migrate until several days (or weeks) later. The main issue to be solved is therefore not how to attract the fish to the old river bed but rather how to create favorable conditions in the old river bed so that migrating fish are more inclined to take that path upstream.

  • 17.
    Andersson, H.M.
    et al.
    Luleå tekniska universitet.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Synnergren, Per
    Luleå tekniska universitet.
    Application of digital speckle photography to measure thickness variations in the vacuum infusion process2003In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 24, no 3, p. 448-455Article in journal (Refereed)
    Abstract [en]

    A new method to measure the movement of the flexible bag used in vacuum infusion is presented. The method is based on an in-house developed stereoscopic digital speckle photography system (DSP). The advantage with this optical method, which is based on cross-correlation, is that the deflection of a large area can be continuously measured with a great accuracy (down to 10 μm. The method is at this stage most suited for research but can in the long run also be adopted in production control and optimization. By use of the method it was confirmed that a ditch is formed at the resin flow front and that there can be a considerable and seemingly perpetual compaction after complete filling. The existence of the ditch demonstrates that the stiffness of the reinforcement can be considerably reduced when it is wetted. Hence, the maximum fiber volume fraction can be larger than predicted from dry measurements of preform elasticity. It is likely that the overall thickness reduction after complete filling emanates from lubrication of the fibers combined with an outflow of the resin. Besides, the cross-linking starts and the polymer shrinks. Hence, the alteration in height will continue until complete cross-linking is reached.

  • 18. Andersson, Magnus
    et al.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Långström, R.
    Luleå tekniska universitet.
    Development of guidelines for the vacuum infusion process2000In: Proceedings of the 8th International Conference on Fibre Reinforced Composites, FRC 2000: Centre for Composite Materials Engineering, University of Newcastle, UK, 13 - 15 September 2000 / [ed] A. G. Gibson, Cambridge: Woodhead Publishing Materials , 2000, p. 113-120Conference paper (Refereed)
    Abstract [en]

    The current trend towards increased use of vacuum infusion moulding for large surface area parts has increased the interest for an advanced modelling of the process. This paper presents a detailed experimental investigation of laminate thickness and out-of-plane flow front shape during impregnation of high permeability reinforcement on top of a non-crimp fabric reinforcement lay-up. The goal with the experiments is to increase the understanding of the process and to provide accurate data that can later be used for validation of numerical models. The laminate thickness was measured during impregnation with a stereoscopic digital speckle photography system and the flow front shape was determined by tracking of colour marks in the stacking. The laminate lay-ups studied are different combinations of non-crimp fabrics and flow layers while the resin used was a polyester developed specifically for vacuum infusion moulding. Results are presented both for the instantaneous thickness and the flow front shape for several different material combinations. It was found that the skewness of the flow front became more pronounced with increasing number of flow layers when the number of non-crimp fabric layers was kept constant. As a first step towards a complete numerical model of the impregnation process a simplified model for the compressibility and a proven model for permeability was implemented in a commercial CFD package that can handle moving boundaries and moving flow fronts. Only a qualitative comparison with experiments was done but the conclusion was that the overall behaviour of the model was encouraging. A validation of the numerical model based on the measurements in this paper is under development.

  • 19. Andersson, Magnus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Numerical model for vacuum infusion manufacturing of polymer composites2003In: International journal of numerical methods for heat & fluid flow, ISSN 0961-5539, E-ISSN 1758-6585, Vol. 13, no 3, p. 383-394Article in journal (Refereed)
    Abstract [en]

    The focus is set on the development and evaluation of a numerical mgodel describing the impregnation stage of a method to manufacture fibre reinforced polymer composites, namely the vacuum infusion process. Examples of items made with this process are hulls to sailing yachts and containers for the transportation industry. The impregnation is characterised by a full 3D flow in a porous medium having an anisotropic, spatial- and time-dependent permeability. The numerical model has been implemented in a general and commercial computational fluid dynamic software through custom written subroutines that: couple the flow equations to the equations describing the stiffness of the fibre reinforcement; modify the momentum equations to account for the porous medium flow; remesh the computational domain in each time step to account for the deformation by pressure change. The verification of the code showed excellent agreement with analytical solutions and very good agreement with experiments. The numerical model can easily be extended to more complex geometry and to other constitutive equations for the permeability and the compressibility of the reinforcement.

  • 20. Andersson, Magnus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Långström, R.
    Swedish Institute of Composites, Piteå.
    Flow-enhancing layers in the vacuum infusion process2002In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 23, no 5, p. 895-901Article in journal (Refereed)
    Abstract [en]

    The current trend towards increased use of vacuum infusion molding for large surface-area parts has increased the interest in an advanced modeling of the process. Because the driving pressure is limited to 1 atmosphere, it is essential to evaluate possible ways to accelerate the impregnation. One way of doing this is to use layers of higher permeability within the reinforcing stack, i.e. flow-enhancing layers. We present an experimental investigation of the flow front shape when using such layers. The through-thickness flow front was observed by making a number of color marks on the glass-mats forming the reinforcing stack, which became visible when the resin reached their position. The in-plane flow front was derived from observations of the uppermost layer. It turned out that existing analytical models agree very well with the experiments if effective permeability data is used, that is, permeability obtained from vacuum infusions. However, the fill-time was nearly twice as long as predicted from permeability data obtained in a stiff tool. This rather large discrepancy may be due to certain features of a flexible mold half and is therefore a topic for further research. The lead-lag to final thickness ratio is dependent on the position of the flow front and ranges form 5 to 10 for the cases tested. Interestingly the lead-lag has a miximum close to the inlet.

  • 21. Andersson, Magnus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Langhans, N.
    EADS Military Aircraft, Munich.
    Computational fluid dynamics applied to the vacuum infusion process2005In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 26, no 2, p. 231-239Article in journal (Refereed)
    Abstract [en]

    An all-purpose computational fluid dynamics software is used for simulations of the vacuum infusion process. The study comprises simulations of a full three-dimensional two-phase flow through a porous medium. The medium that has an anisotropic, spatial- and time-dependent permeability is located in a complex mold with moving boundaries. With this generalization, different material combinations, processing conditions, and even other manufacturing techniques can be evaluated. The strength of the presented approach is exemplified by simulations of mold filling of a real part, using a typical vacuum infusion set-up. In addition to the overall development of the model, a number of specific aspects and phenomena are investigated and evaluated. Local lead of the flow front and a minor influence in overall flow front lead-lag, with no influence on the fill time, is the result of simulations of edge effects due to poor preform fitting.

  • 22. Andersson, Magnus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Langhans, N.
    Numerical simulation of the vacuum infusion process2006In: Experimental techniques and design in composite materials (ETDCM6): "Sixth International Seminar on Experimental Techniques and Design in Composite Materials" which was held at Padova in June 2003 / [ed] Marino Quaresimin, Amsterdam: Elsevier, 2006Conference paper (Refereed)
  • 23.
    Andersson, Robin
    et al.
    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.
    Andreasson, Patrik
    Vattenfall Research & Development.
    Hellström, J. Gunnar I.
    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.
    Grade of geometric resolution of a rough surface required for accurate prediction of pressure and velocities in water tunnels2014Conference paper (Refereed)
  • 24. Baart, Pieter
    et al.
    Green, Torbjörn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Li, Jinxia
    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.
    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.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Contaminant particle migration in a double restriction seal2013In: Proceedings of the STLE Annual Meeting and Exhibition 2013, Detroit MI, USA., STLE , 2013, p. 125-Conference paper (Refereed)
    Abstract [en]

    Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile.In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication

  • 25. Baart, Pieter
    et al.
    Green, Torbjörn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Li, Jinxia
    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.
    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.
    Lugt, Piet
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The influence of speed, grease type, and temperature on radial contaminant particle migration in a double restriction seal2011In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 54, no 6, p. 867-877Article in journal (Refereed)
    Abstract [en]

    Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile. In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication.

  • 26.
    Baart, Pieter
    et al.
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Green, Torbjörn
    Li, Jinxia
    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.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sealing improvements by grease selection in double lip seals and labyrinth seals2012In: 17th ISC: International Sealing Conference ; Stuttgart, Germany, Sept. 13 - 14, 2012, Frankfurt am Main: Fachverband Fluidtechnik im VDMA e.V , 2012Conference paper (Refereed)
  • 27. Bergström, R.
    et al.
    Birkeland, P.A.
    Lundström, Staffan
    Partanen, H.
    Stenberg, R.
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    In-plane permeabilitymeasurements: A Nordic round-robin study1998Report (Other academic)
  • 28.
    Bin Asad, S M Sayeed
    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.
    Andersson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Study the Flow behind a Semi-Circular Step Cylinder (Laser Doppler Velocimetry (LDV) and Computational Fluid Dynamics (CFD))2017In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, no 3, article id 332Article in journal (Refereed)
    Abstract [en]

    Laser Doppler Velocimetry (LDV) measurements, flow visualizations and unsteadyReynolds-Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) simulations havebeen carried out to study the turbulent wake that is formed behind a semi-circular step cylinder ata constant flow rate. The semi-circular cylinder has two diameters, a so-called step cylinder. Theresults from the LDV measurements indicate that wake length and vortex shedding frequency varieswith the cylinder diameter. This implies that a step cylinder can be used to attract fish of differentsize. By visualizations of the formation of a recirculation region and the well-known von Kármánvortex street behind the cylinder are disclosed. The simulation results predict the wake length andshedding frequency well for the flow behind the large cylinder but fail to capture the dynamics ofthe flow near the step in diameter to some extent and the flow behind the small cylinder to a largerextent when compared with measurements.

  • 29.
    Bin Asad, S M Sayeed
    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.
    Andersson, Anders G.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Experimental study of the flow past submerged half-cylinders2017In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1851, article id 020001Article in journal (Refereed)
    Abstract [en]

    This investigation studies the details of the flow behind and over two identical semicircular cylinderspositioned in tandem. Laser Doppler Velocimetry (LDV) measurements are carried out in a laboratory waterflume using two different gap ratios (Sp/d = 1 and Sp/d = 0.5; where Sp indicates distance between the cylindersand d indicates cylinder diameter) under two different flow situations. These LDV measurement are used toderive velocities, formation length and Power spectral density for the various flow conditions. Flowvisualizations are also added in this investigation. The results indicate that the flow is significantly affected dueto gap ratios.

  • 30.
    Bin Asad, S M Sayeed
    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.
    Andersson, Anders
    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.
    A Review of Particle Image Velocimetry for Fish Migration2016In: World Journal of Mechanics, ISSN 2160-049X, E-ISSN 2160-0503, Vol. 6, no 4, p. 131-149Article in journal (Refereed)
    Abstract [en]

    Understanding the flow characteristic in fishways is crucial for efficient fish migration. Flow characteristic measurements can generally provide quantitative information of velocity distributions in such passages; Particle Image Velocimetry (PIV) has become one of the most versatile techniques to disclose flow fields in general and in fishways, in particular. This paper firstly gives an overview of fish migration along with fish ladders and then the application of PIV measurements on the fish migration process. The overview shows that the quantitative and detailed turbulent flow information in fish ladders obtained by PIV is critical for analyzing turbulent properties andvalidating numerical results.

  • 31.
    Bin Asad, S M Sayeed
    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.
    Andersson, Anders
    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.
    Velocity distribution measurements in a fishway like open channel by Laser Doppler Anemometry (LDA)2016In: / [ed] Dancova, P; Vesely, M, 2016Conference paper (Refereed)
    Abstract [en]

    Experiments in an open channel flume with placing a vertical half cylinder barrier have been performed in order to investigate how the upstream velocity profiles are affected by a barrier. An experimental technique using Laser Doppler Velocimetry (LDV) was adopted to measure these velocity distributions in the channel for four different discharge rates. Velocity profiles were measured very close to wall and at 25, 50 and 100 mm upstream of the cylinder wall. For comparing these profiles with well-known logarithmic velocity profiles, velocity profiles were also measured in smooth open channel flow for all same four discharge rates. The results indicate that regaining the logarithmic velocity profiles upstream of the half cylindrical barrier occurs at 100 mm upstream of the cylinder wall.

  • 32.
    Burström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Antos, Dorota
    Rzeszów University of Technology.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    A CFD-based evaluation of Selective Non-Catalytic Reduction of Nitric Oxide in iron ore grate-kiln plants2015In: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 15, no 1, p. 32-46Article in journal (Refereed)
    Abstract [en]

    The overall goal of this study is to explore the function of selective non-catalytic reduction of nitric oxide (NO) in iron ore grate-kiln plants. Computational fluid dynamics is used to model the flow and the injection of urea and cyanuric acid reagents. Temperature, residence time and inlet NO content are varied, and the effects on the reduction of NO are studied. The simulations show that the use of urea results in a higher reduction of NO within the temperature window investigated as compared to cyanuric acid; however, urea cannot be used for NO reduction over the entire range of applicable temperatures. Cyanuric acid is usable within the entire temperature range for high NO content (i.e., 300 ppm) in the flue gas, but it is not effective for low NO concentration (i.e., 150 ppm). Moreover, the simulations indicate that temperature has a larger influence on the NO reduction than the residence time.

  • 33.
    Burström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Antos, Dorota
    Rzeszów University of Technology.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    A validated CFD model for prediction of selective non-catalytic reduction of nitric oxide by cyanuric acid2016In: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 16, no 2, p. 108-117Article in journal (Refereed)
    Abstract [en]

    A CFD model for selective non-catalytic reduction of nitric oxide by cyanuric acid (RAPid REduction of Nitrogen Oxides, RAPRENOx process) is compared against reactor experiments. The numerical simulations were carried out solving the flow field. A model for the RAPRENOx chemistry was then included in the model enabling a study of the chemistry in the reactor. The simulations showed that the proposed chemistry model is valid under certain conditions. There is an especially good agreement for high O2 concentrations while the model failed in reproducing the experimental data for 0% H2O

  • 34.
    Burström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Frishfelds, Vilnis
    Liepaja University .
    Ljung, Anna-Lena
    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.
    Marjavaara, B. Daniel
    LKAB, Kiruna.
    Modelling heat transfer during flow through a random packed bed of spheres2018In: Heat and Mass Transfer, ISSN 0947-7411, E-ISSN 1432-1181, Vol. 54, no 4, p. 1225-1245Article in journal (Refereed)
    Abstract [en]

    Heat transfer in a random packed bed of monosized iron ore pellets is modelled with both a discrete three-dimensional system of spheres and a continuous Computational Fluid Dynamics (CFD) model. Results show a good agreement between the two models for average values over a cross section of the bed for an even temperature profiles at the inlet. The advantage with the discrete model is that it captures local effects such as decreased heat transfer in sections with low speed. The disadvantage is that it is computationally heavy for larger systems of pellets. If averaged values are sufficient, the CFD model is an attractive alternative that is easy to couple to the physics up- and downstream the packed bed. The good agreement between the discrete and continuous model furthermore indicates that the discrete model may be used also on non-Stokian flow in the transitional region between laminar and turbulent flow, as turbulent effects show little influence of the overall heat transfer rates in the continuous model.

  • 35.
    Burström, Per
    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, Fluid and Experimental Mechanics.
    Ljung, Anna-Lena
    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.
    Discrete and continuous modelling of convective heat transport in a thin porous layer of mono sized spheres2017In: Heat and Mass Transfer, ISSN 0947-7411, E-ISSN 1432-1181, Vol. 53, no 1, p. 151-160Article in journal (Refereed)
    Abstract [en]

    Convective heat transport in a relatively thin porous layer of monosized particles is here modeled. The size of the particles is only one order of magnitude smaller than the thickness of the layer. Both a discrete three-dimensional system of particles and a continuous one-dimensional model are considered. The methodology applied for the discrete system is Voronoi discretization with minimization of dissipation rate of energy. The discrete and continuous model compares well for low velocities for the studied uniform inlet boundary conditions. When increasing the speed or for a thin porous layer however, the continuous model diverge from the discrete approach if a constant dispersion is used in the continuous approach. The new result is thus that a special correlation must be used when using a continuous model for flow perpendicular to a thin porous media in order to predict the dispersion in proper manner, especially in combination with higher velocities.

  • 36.
    Burström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Frishfelds, Vilnis
    Liepaja University.
    Ljung, Anna-Lena
    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 Research and Development.
    Grate aerodynamic: Model strategies for gas flow through a 2D iron ore pellet bed2014Conference paper (Refereed)
  • 37.
    Burström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Marjavaara, B. Daniel
    LKAB.
    Töyrä, Simon
    LKAB.
    CFD-modelling of selective non-catalytic reduction of NOx in grate-kiln plants2009In: Seventh International Conference on CFD in the Minerals and Process Industries: CSIRO, Melbourne, Australia 9-11 December 2009, CSIRO Publishing, 2009, p. 1-6Conference paper (Refereed)
    Abstract [en]

    The overall goal of this project is to find out if selective non-catalytic reduction (SNCR) technologies can be used in grate-kiln plants for NOx reduction. The technique has, to the best knowledge of the authors, never been used in this context before despite that it is commonly used in cement and waste incineration plants.   A Computational Fluid Dynamic model of parts of a real grate was created and numerical simulations with a commercial code was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. The simulations show promising results for SNCR with urea but not with ammonia.

  • 38.
    Burström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Marjavaara, Daniel
    LKAB.
    Töyrä, Simon
    LKAB.
    CFD-modelling of selective non-catalytic reduction of NOx in grate-kiln plants2010In: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 10, no 5/6, p. 284-291Article in journal (Refereed)
    Abstract [en]

    The overall goal of this project is to find out if Selective Non-Catalytic Reduction (SNCR) technologies can be used in grate-kiln plants for NOx reduction. The technique has, to the best knowledge of the authors, never been used in this context before, despite that it is commonly used in cement and waste incineration plants. A model for spray injection into the grate was included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. The simulations indicate that the SNCR-technique works with urea, but not with ammonia.

  • 39.
    Burström, Per
    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.
    CFD-modellering av selektiv icke-katalytisk reduktion av NOX under tillverkning av järnmalmspellets2011Conference paper (Refereed)
    Abstract [sv]

    Syftet med projektet är att utreda om rökgasreningstekniken selektiv icke-katalytiskreduktion (SNCR) kan användas till NOX-reduktion under tillverkning av järnmalmspellets.Tekniken har till vår vetskap aldrig använts i detta sammanhang. SNCR-tekniken innebäratt man vid hög temperatur injicerar ett reduktionsmedel i rökgaserna vilket reagerar medkväveoxiderna och bildar kvävgas och vattenånga.En strömningsmekanisk beräkningsmodell av processen har tagits fram och numeriskasimuleringar har genomförts med en kommersiell kod för att lösa flödesfältet. Sedaninkluderades en modell för sprayinjektion i processen vilket möjliggjorde en undersökningav den övergripande mixningen mellan de injicerade dropparna och den NOX-förorenaderökgasen. Det övergripande resultatet är att SNCR-tekniken fungerar med urea somreduktionsmedel men inte med ammoniak.

  • 40. Dahlbäck, L.M.
    et al.
    Lundström, Staffan
    A method to measure wetting between resin and reinforcement1995In: Proceedings of the Tenth International Conference on Composite Materials: [Proceedings of ICCM-10] : Whistler, British Columbia, Canada, August 14th-18th, 1995 / [ed] Anoush Poursartip; Ken Street, Vancouver: Bentham Press , 1995, Vol. 3, p. 293-300Conference paper (Refereed)
  • 41.
    Das, Samir
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ganesh, S. Jai
    Centre for Energy, Indian Institute of Technology Jodhpur, Ratanada.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Modelling of a groundwater mound in two-dimensional heterogeneous unconfined aquifer in response to precipitation recharge2015In: Journal of hydrologic engineering, ISSN 1084-0699, E-ISSN 1943-5584, Vol. 20, no 7, article id 4014081Article in journal (Refereed)
    Abstract [en]

    The paper deals with the transient semi-analytical solution of linearized Boussinesq equations characterizing the development of groundwater mound in an unconfined two-dimensional heterogeneous aquifer under vertical recharge conditions. The finite aquifer consists of two rectangular basins surrounded by open water bodies and shares a common impermeable or permeable boundary at the mid plane. The governing equations are solved by applying the Laplace transform and finite Fourier sine transform techniques. Accordingly, analytical expressions for water heads for two rectangular basins are obtained for various scenarios. The applicability of the solutions has been illustrated with the help of a case study and numerical examples, considering various cases. The region wise development of the groundwater mound indicates that the effect of heterogeneity becomes significant for small time duration whereas for long time it becomes insignificant. This result can have application in land reclamation problems in the presence of localized recharge where the reclamation displaces the ground water divide and changes the groundwater conditions in the entire region

  • 42. Ebermark, Sofia
    et al.
    Marjavaara, Daniel
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Pressning av SMC: numeriska tryckfältsberäkningar med hjälp av inversmodellering2007In: Svenska Mekanikdagar 2007: Program och abstracts / [ed] Niklas Davidsson; Elianne Wassvik, Luleå: Luleå tekniska universitet, 2007, p. 74-Conference paper (Other academic)
  • 43.
    Fabricius, John
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hellström, Gunnar
    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.
    Miroshnikova, Elena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Wall, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Darcy's law for flow in a periodic thin porous medium confined between two parallel plates2016In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 115, no 3, p. 473-493Article in journal (Refereed)
    Abstract [en]

    We study stationary incompressible fluid flow in a thin periodic porous medium. The medium under consideration is a bounded perforated 3D-domain confined between two parallel plates. The distance between the plates is \(\delta \), and the perforation consists of \(\varepsilon \)-periodically distributed solid cylinders which connect the plates in perpendicular direction. Both parameters \(\varepsilon \), \(\delta \) are assumed to be small in comparison with the planar dimensions of the plates. By constructing asymptotic expansions, three cases are analysed: (1) \(\varepsilon \ll \delta \), (2) \(\delta /\varepsilon \sim \text {constant}\) and (3) \(\varepsilon \gg \delta \). For each case, a permeability tensor is obtained by solving local problems. In the intermediate case, the cell problems are 3D, whereas they are 2D in the other cases, which is a considerable simplification. The dimensional reduction can be used for a wide range of \(\varepsilon \) and \(\delta \) with maintained accuracy. This is illustrated by some numerical examples.

  • 44.
    Fallahjoybari, Nima
    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.
    Maerefat, Mehdi
    Department of Mechanical Engineering, Tarbiat Modares University.
    Nimvari, Majid E.
    Department of Mechanical Engineering, Tarbiat Modares University, Faculty of Engineering Technologies, Amol University of Special Modern Technologies, Amol.
    Numerical Computation of Macroscopic Turbulent Quantities in a Porous Medium: an Extemsion to a macroscopic Turbulent model2016In: Journal of Porous Media, ISSN 1091-028X, E-ISSN 1934-0508, Vol. 19, no 6, p. 497-513Article in journal (Refereed)
    Abstract [en]

    A numerical study is conducted using a standard numerical model for a porous medium consisting of a staggered arrangement of square cylinders. Fully developed macroscopic turbulent kinetic energy and dissipation rate are derived and analyzed for different porosities of the medium at different Reynolds numbers. The results obtained are used to extend the applicability range of an existing macroscopic turbulence model in porous media to low-Reynolds-number turbulent flows. It is shown that the levels of normalized macroscopic turbulent kinetic energy and dissipation rate are not constant over the entire range of Reynolds number. These quantities increase from lower levels at low Reynolds numbers up to an asymptotic value being independent of Reynolds number. The constants in the closure expression of the macroscopic turbulence equations are modified using the present results. Finally, in order to highlight the importance of the present modifications, the results of the macroscopic turbulence model before and after the modifications are compared for two cases.

  • 45.
    Fernberg, S Patrik
    et al.
    Swerea SICOMP AB.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Fibre reinforced polymer composites based on nanostructured constituents2008In: White Book: Polymer Nanoscience and Nanotechnology, a European Perspective, 2008, p. 233-256Chapter in book (Other academic)
  • 46.
    Fernberg, S.P.
    et al.
    Luleå tekniska universitet.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sandlund, E.J.
    Öhgren, I.
    Particle Distribution Mechanisms in Infusion Moulded Composites2004In: From nano-scale interactions to engineering structures: ECCM 11, 11th European Conference on Composite Materials ; May 31 - June 3, 2004, Rhodes, Greece / [ed] Costas Galiotis, Rhodos, 2004Conference paper (Refereed)
  • 47.
    Fernberg, S.P.
    et al.
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Sandlund, E.J.
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mechanisms controlling particle distribution in infusion molded composites2006In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 25, no 1, p. 59-70Article in journal (Refereed)
    Abstract [en]

    This article presents results from an experimental investigation in which two grades of aluminatrihydroxide (ATH) particles are added to liquid resin and used in infusion molding experiments. Based on the results, potential key mechanisms controlling resin flow and hence also the final particle distribution are proposed. A pore doublet model is proposed to explain the seemingly random spatial distribution of particle-dense regions within the final material. These dense regions are found within flow channels, at locations where local shear strain rates are low. This suggests that they are formed as a consequence of a Bingham type of viscosity behavior observed for the suspension and/or due to filtering of particles during fiber bundle impregnation.

  • 48. Frishfelds, Vilnis
    et al.
    Hellström, J. Gunnar I.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Flow-induced deformation of non-crimp fabrics during composites manufacturing2009In: Proceedings of ITP2009: Interdisciplinary Transport Phenomena VI: Fluid, Thermal, Biological, Materials and Space Sciences, October 4-9, 2009, Volterra, Italy, 2009, article id ITP-09-52Conference paper (Refereed)
    Abstract [en]

    Flow induced alteration in permeability of deformable systems of fibres is studied. Low Reynolds number transversal flow through random arrays of aligned cylinders is considered by using a combined methodology of directly solving the twodimensional Navier-Stokes equations for the flow in the vicinity of a single fibre and minimisation of the dissipation rate in a system of fibres. The permeability of large random arrays increases always which is most apparent for compact systems with equal sized fibres. The permeability can also decrease but then for structured or small systems. The elastic deformations of fibre bundles are calculated basing microscopic fibre structure.

  • 49. Frishfelds, Vilnis
    et al.
    Hellström, J. Gunnar I.
    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.
    Fluid flow induced deformation of porous medium: modeling of the no erosion filter test experiment2010In: Proceedings of the 3rd International Conference on Porous Media and its Applications in Science and Engineering: ICPM3, 2010Conference paper (Refereed)
    Abstract [en]

    To study internal erosion in depth it is necessary to know either the detailed flow or how it varies in a statistical manner. It is also important to know how the internal erosion process initiates and progresses due to the fluid flow-induced forces. The underlying reason for this is that internal erosion will initiate exactly where the forces from the fluid are higher than the retaining forces that keep the particles together. Hence, a new model is here developed where fluid flow induced deformations of a large number of particles is studied. The model is applied to the No Erosion Filter test and simulated results resemble experimental results from the literature. The NEF test is used to investigate parameters such as the hydraulic conductivity and also in detail the process of internal erosion. The simulations are performed on different set-ups to exemplify successful and unsuccessful sealing. In the model, minimization of the dissipation rate of energy is accompanied with discretization of the system with modified Voronoi diagrams. Then Computational Fluid Dynamics is applied to solve the flow within each part of the Voronoi diagrams. Different parameters, such as the vorticity, calculated with the CFD-software are then used as input to the Monte Carlo-simulations. An overall good conformity between simulated results and experimental results from the literature is obtained.

  • 50.
    Frishfelds, Vilnis
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Hellström, J. Gunnar I.
    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.
    Alteration of permeability caused by transversal flow-induced deformation of fibres during composites manufacturing2010In: Proceedings of The 10th International Conference on Flow Processes in Composite Materials (FPCM10): Monte Verità, Ascona, CH – July 11-15, 2010, 2010Conference paper (Refereed)
1234567 1 - 50 of 316
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