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Alnersson, G., Lejon, E., Zrida, H., Aitomäki, Y., Ljung, A.-L. & Lundström, T. S. (2023). 3D flow and fibre orientation modelling of compression moulding of A-SMC: simulations and experimental validation in squeeze flow. Paper presented at 20th European Conference on Composite Materials (ECCM20), Lausanne, Switzerland, June 26-30, 2022. Functional Composite Materials, 4, Article ID 11.
Open this publication in new window or tab >>3D flow and fibre orientation modelling of compression moulding of A-SMC: simulations and experimental validation in squeeze flow
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2023 (English)In: Functional Composite Materials, E-ISSN 2522-5774, Vol. 4, article id 11Article in journal (Refereed) Published
Abstract [en]

Sheet Moulding Compound (SMC) based composites have a large potential in industrial contexts due to the possibility of achieving comparatively short manufacturing times. It is however necessary to be able to numerically predict both mechanical properties as well as manufacturability of parts.

In this paper a fully 3D, semi-empirical model based on fluid mechanics for the compression moulding of SMC is described and discussed, in which the fibres and the resin are modelled as a single, inseparable fluid with a viscosity that depends on volume fraction of fibres, shear strain rate and temperature. This model is applied to an advanced carbon-fibre SMC with a high fibre volume fraction (35%). Simulations are run on a model of a squeeze test rig, allowing comparison to experimental results from such a rig. The flow data generated by this model is then used as input for an Advani-Tucker type of model for the evolution of the fibre orientation during the pressing process. Numerical results are also obtained from the software 3DTimon. The resulting fibre orientation distributions are then compared to experimental results that are obtained from microscopy. The experimental measurement of the orientation tensors is performed using the Method of Ellipses. A new, automated, accurate and fast method for the ellipse fitting is developed using machine learning. For the studied case, comparison between the experimental results and numerical methods indicate that 3D Timon better captures the random orientation at the outer edges of the circular disc, while 3D CFD show larger agreement in terms of the out-of-plane component. One of the advantages of the new image technique is that less work is required to obtain microscope images with a quality good enough for the analysis.

Place, publisher, year, edition, pages
Springer Nature, 2023
Keywords
Sheet moulding compound, Numerical modelling, High volume fraction, Method of ellipses, Machine learning
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-103899 (URN)10.1186/s42252-023-00049-9 (DOI)
Conference
20th European Conference on Composite Materials (ECCM20), Lausanne, Switzerland, June 26-30, 2022
Projects
PROSICOMP II
Funder
VinnovaSwedish Energy AgencySwedish Research Council FormasSwedish Transport Administration
Note

Godkänd;2024;Nivå 0;2024-01-24 (hanlid);

Funder: Vehicle Strategic research and Innovation (FFI);

Full text license: CC BY 

Available from: 2024-01-24 Created: 2024-01-24 Last updated: 2024-01-24Bibliographically approved
Moosavi, A., Ljung, A.-L. & Lundström, S. (2023). A comparative study on thermo-fluid characteristics of free and wall-bounded cross-flow heat exchangers. Thermal Science and Engineering Progress, 40, Article ID 101746.
Open this publication in new window or tab >>A comparative study on thermo-fluid characteristics of free and wall-bounded cross-flow heat exchangers
2023 (English)In: Thermal Science and Engineering Progress, ISSN 2451-9057, Vol. 40, article id 101746Article in journal (Refereed) Published
Abstract [en]

In recent years, wall-bounded cross-flow heat exchangers have gained significant attention for battery cooling applications. Due to similarities in geometry, these systems are often evaluated based on the heat and flow knowledge of free cross-flow heat exchangers. To determine the reliability of this assumption, this study performs a numerical comparison of the thermo-fluid behavior of wall-bounded and free cross-flow heat exchangers. Both heat exchangers have similar dimensions, with transverse and longitudinal pitch ratios of 2.074 and 1.037, respectively, and are investigated at a Reynolds number of 40000 using the Unsteady Reynolds-Averaged Navier–Stokes (URANS) method. It is observed that the  transition model provides the most accurate predictions of the flow field when compared to available experimental data. The results suggest that for wall-bounded heat exchangers with an aspect ratio of 2 or larger, the flow behavior in the central flow region resembles that of a free heat exchanger, but with varying magnitudes due to the increase in velocity in the core region to counterbalance the reduction near the walls. The area-averaged mean Nusselt number from 2D and 3D models for free heat exchangers shows no significant difference compared to wall-bounded heat exchangers. However, there are considerable differences in the local Nusselt number distributions in the angular and spanwise directions. Overall, it is determined that certain conditions must be satisfied to ensure that applying the thermo-fluid characteristics of a free cross-flow heat exchanger to wall-bounded cross-flow heat exchangers in battery thermal management systems is accurate.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Heat exchanger, Cross-flow, URANS model, Wall effect, Battery thermal management system
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-95442 (URN)10.1016/j.tsep.2023.101746 (DOI)000955267900001 ()2-s2.0-85149617478 (Scopus ID)
Funder
StandUp, 197140
Note

Validerad;2023;Nivå 2;2023-03-20 (joosat);

Licens fulltext: CC BY License

This article has previously appeared as a manuscript in a thesis.

Available from: 2023-02-01 Created: 2023-02-01 Last updated: 2023-04-21Bibliographically approved
Moosavi, A., Ljung, A.-L. & Lundström, T. S. (2023). A study on the effect of cell spacing in large-scale air-cooled battery thermal management systems using a novel modeling approach. Journal of Energy Storage, 72, Article ID 108418.
Open this publication in new window or tab >>A study on the effect of cell spacing in large-scale air-cooled battery thermal management systems using a novel modeling approach
2023 (English)In: Journal of Energy Storage, ISSN 2352-152X, E-ISSN 2352-1538, Vol. 72, article id 108418Article in journal (Refereed) Published
Abstract [en]

Recent studies have revealed that effective thermal management systems are necessary to maintain the performance, lifespan, and safety of lithium battery systems. A unique and novel modeling approach is presented in this work with the aim of estimating the thermal performance of air-based cooling systems for large-scale lithium battery packages. The overall model consists of sub-models, including an analytical model for battery cells and a numerical heat and flow model for the battery module, which are validated against experimental data and empirical correlations, respectively. The chosen approach implies that the sub-models can operate independently, allowing accurate transient simulations with reduced processing time. The model is employed to evaluate the effect of cell spacing on the thermal performance of an air-cooled battery system designed for a hybrid electric vehicle. The results demonstrate that the maximum temperature within the cells positively correlates with transverse and longitudinal pitch ratios; however, the maximum temperature difference in the module has a negative correlation with these pitch ratios. In contrast, temperature uniformity shows non-monotonic behavior, making it an applicable criterion to balance between temperature rise and thermal gradients. Moreover, considerable temperature non-uniformity is noted in the early rows, which becomes less significant as pitch ratios decrease.

Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
Analytical model, Battery thermal management system, Cylindrical lithium battery, Spacing effect, URANS model
National Category
Energy Engineering
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-99551 (URN)10.1016/j.est.2023.108418 (DOI)2-s2.0-85166477264 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-08-14 (joosat);

Funder: StandUp for Energy

Licens fulltext: CC BY License

Available from: 2023-08-14 Created: 2023-08-14 Last updated: 2023-08-28Bibliographically approved
Jouybari, N. F., Engberg, B., Persson, J., Berg, J.-E. & Lundström, T. S. (2023). An investigation of forces on a representative surface in a pulp flow through rotating and non-rotating grooves. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 45(5), Article ID 280.
Open this publication in new window or tab >>An investigation of forces on a representative surface in a pulp flow through rotating and non-rotating grooves
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2023 (English)In: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 45, no 5, article id 280Article in journal (Refereed) Published
Abstract [en]

Softwood pulp flow in rotating and non-rotating grooves is numerically simulated in the present study to investigate the fluid flow and the forces acting on a representative surface mounted in the groove. The viscosity of softwood pulp with various consistencies is available from the measurements reported in the literature providing the opportunity to examine the effects of fiber consistency on the velocity and pressure distribution within the groove. The simulations are carried out in OpenFOAM for different values of gap thickness, angular velocity and radial positions from which the pressure coefficient and shear forces values are obtained. It is found that the shear forces within the gap increase linearly with the angular velocity for all fiber consistencies investigated and in both grooves. Also, this behavior can be successfully predicted by modeling the gap flow as a Couette flow in a two-dimensional channel. Meanwhile, a more detailed analysis of the flow kinetic energy close to the stagnation point using Bernoulli’s principle is carried out to provide a better understanding of the pressure coefficient variation with angular velocity in the non-rotating groove. A comparison of pressure coefficients obtained numerically with those calculated by considering the compression effects revealed that the comparison effects are dominating in the pulp flow within the groove.

Place, publisher, year, edition, pages
Springer, 2023
Keywords
Numerical simulation, Softwood pulp, Non-rotating, Rotating, Groove
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-97682 (URN)10.1007/s40430-023-04204-y (DOI)000980505300001 ()2-s2.0-85159857477 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-05-29 (joosat);

Licens fulltext: CC BY License

Available from: 2023-05-29 Created: 2023-05-29 Last updated: 2023-10-11Bibliographically approved
Barestrand, H. A., Ljung, A.-L., Summers, J. & Lundström, T. S. (2023). Modeling Convective Heat Transfer of Air in a Data Center Using OpenFOAM: Evaluation of the Boussinesq Buoyancy Approximation. OpenFOAM® Journal, 3, 146-158
Open this publication in new window or tab >>Modeling Convective Heat Transfer of Air in a Data Center Using OpenFOAM: Evaluation of the Boussinesq Buoyancy Approximation
2023 (English)In: OpenFOAM® Journal, E-ISSN 2753-8168, Vol. 3, p. 146-158Article in journal (Refereed) Published
Abstract [en]

Achieving energy and cooling efficiency in data center convective air flow and heat transfer can be a challenging task. Among different numerical methods to work with such issues is the Finite Volume Method in Computational Fluid Dynamics. This work evaluates the performance of two such solvers provided by OpenFOAM® in solving this type of convective heat-transfer problem, namely BuoyantBoussinesqPimpleFOAM and BuoyantPimpleFOAM. This is done for two different flow configurations of significantly different Richardson number. To sufficiently resolve the flow, grid sizing effects are elucidated by way of the kernel density estimate. It determines the volume distribution of the temperature in the data center configuration. For the k-epsilon turbulence model used here, it was found that the compressible solver performs faster and requires less grid resolution for both flow configurations. This is attributed to the nature of the boundary conditions which are set such that the mass flow conservation per server rack and cooling unit is achieved. Transient solutions are found to provide better iterative convergence for cases that involves buoyancy, compressibility and flow separation. This is, in comparison to steady-state solutions where artificial numerical pressure drop is found, to depend on the momentum relaxation factors for the convective case with a higher Richardson number.

Place, publisher, year, edition, pages
OpenCFD Ltd, 2023
Keywords
fvm, boussinesq, compressible, heat transfer, kde, k-epsilon, Richardson
National Category
Fluid Mechanics and Acoustics Energy Engineering
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-99360 (URN)10.51560/ofj.v3.59 (DOI)
Funder
Swedish Energy Agency, 43090-2
Note

Godkänd;2023;Nivå 0;2023-08-09 (hanlid)

Available from: 2023-08-09 Created: 2023-08-09 Last updated: 2023-12-12Bibliographically approved
Forslund, T. O. .., Larsson, I. A., Hellström, J. G. & Lundström, T. S. (2023). Steady-State Transitions in Ordered Porous Media. Transport in Porous Media, 149(2), 551-577
Open this publication in new window or tab >>Steady-State Transitions in Ordered Porous Media
2023 (English)In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 149, no 2, p. 551-577Article in journal (Refereed) Published
Abstract [en]

Previously performed experiments on flow through an ordered porous media cell with tomographic particle image velocimetry reveal a complex three-dimensional steady-state flow pattern. This flow pattern emerge in the region where inertial structures have been previously reported for a wide range of packings. The onset of these steady-state inertial flow structures is here scrutinized for three different types of packing using a finite difference method. It is concluded that the onset of the flow structure coincides with a symmetry break in the flow field and discontinuities in the pressure drop, volume averaged body forces and heat transfer. A quantity for identifying the transition is proposed, namely the pressure integral across the solid surfaces. It is also shown that the transition can both increase and decrease the heat transfer dependent on the actual geometry of the porous medium.

Place, publisher, year, edition, pages
Springer Nature, 2023
Keywords
FDM, Pore scale, Ordered porous media, Inertial transition
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-93182 (URN)10.1007/s11242-023-01966-w (DOI)001008440200001 ()2-s2.0-85161891565 (Scopus ID)
Funder
Swedish Research Council, 2017-04390
Note

Validerad;2023;Nivå 2;2023-08-15 (hanlid);

This article has previously appeared as a manuscript in a thesis.

Licens fulltext: CC BY License

Available from: 2022-09-22 Created: 2022-09-22 Last updated: 2023-09-05Bibliographically approved
Barcot, A., Åkerstedt, H. O., Larsson, I. A. & Lundström, S. (2023). Stormwater Uptake in Sponge-Like Porous Bodies Surrounded by a Pond: A Fluid Mechanics Analysis. Water, 15(18), Article ID 3209.
Open this publication in new window or tab >>Stormwater Uptake in Sponge-Like Porous Bodies Surrounded by a Pond: A Fluid Mechanics Analysis
2023 (English)In: Water, E-ISSN 2073-4441, Vol. 15, no 18, article id 3209Article in journal (Refereed) Published
Abstract [en]

In this work, a previously published model for the water up take of stormwater in sponge-like porous bodies by the group is further developed. This is done by investigating the highest-performing model and considering the water uptake from the surroundings of a pond and rain-infiltrated soil. This implies that water uptake from impermeable to partially permeable surfaces is examined. Hence, the following cases are considered: (1) impervious bottom surface and no precipitation, (2) impervious bottom surface with precipitation, (3) permeable soil with no precipitation, and (4) permeable soil with precipitation. A mathematical model covering all these cases is presented, where the governing equations are the mass conservation and Darcy’s law together with an assumption of a sharp wetting front being a first-order approximation of the complete Richard’s equation. Results for the water uptake height, pond depth, and wetting front are computed numerically and plotted against time. Analytical solutions are also presented in certain cases, and critical values are obtained. The parametric study includes variations in the ratio of the model- to the surrounding ground surface area, initial pond depth, precipitation, and soil characteristics. To exemplify, the time it takes to absorb the water from the pond after a precipitation period is presented. The results are related to the Swedish rainfall data of 1 h duration with a return period of 10 years. When evaluating efficiency, the focus is on the absorption time. Results vary considerably, demonstrating a general trend that with soil infiltration, the water absorption rate is higher. For most cases, the considered water amount is absorbed completely, although depending on the parameters and conditions. These results serve to optimize the model for each of the cases. The main focus of the research lies in the theoretical aspect.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
stormwater, porous media, water uptake, mathematical modelling, sharp wetting front, infiltration, water absorption
National Category
Water Engineering
Research subject
Fluid Mechanics; Centre - Centre for Stormwater Management (DRIZZLE)
Identifiers
urn:nbn:se:ltu:diva-101321 (URN)10.3390/w15183209 (DOI)
Funder
Vinnova
Note

Validerad;2023;Nivå 2;2023-09-12 (joosat);

CC BY 4.0 License

Available from: 2023-09-12 Created: 2023-09-12 Last updated: 2023-09-12Bibliographically approved
Alnersson, G., Aitomäki, Y., Ljung, A.-L. & Lundström, T. S. (2022). 3D Flow and Fibre Orientation Modelling of Compression Moulding of A-SMC: Simulation and Validation in Squeeze Flow. In: Vassilopoulos, Anastasios P.; Michaud, Véronique (Ed.), ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability. Paper presented at 20th European Conference on Composite Materials (ECCM20), Lausanne, Switzerland, June 26-30, 2022 (pp. 250-255). EPFL Lausanne, Composite Construction Laboratory, 2
Open this publication in new window or tab >>3D Flow and Fibre Orientation Modelling of Compression Moulding of A-SMC: Simulation and Validation in Squeeze Flow
2022 (English)In: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability / [ed] Vassilopoulos, Anastasios P.; Michaud, Véronique, EPFL Lausanne, Composite Construction Laboratory , 2022, Vol. 2, p. 250-255Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
EPFL Lausanne, Composite Construction Laboratory, 2022
Keywords
Sheet Moulding Compound, Numerical Simulation, Fibre Orientation Modelling
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-96910 (URN)2-s2.0-85149401264 (Scopus ID)
Conference
20th European Conference on Composite Materials (ECCM20), Lausanne, Switzerland, June 26-30, 2022
Projects
PROSICOMP II
Funder
VinnovaSwedish Energy AgencySwedish Transport Administration
Note

ISBN för värdpublikation: 978-2-9701614-0-0;

Full text license: CC BY-NC

Available from: 2023-05-15 Created: 2023-05-15 Last updated: 2024-01-24Bibliographically approved
Forslund, T. O. M., Larsson, I. A., Hellström, J. G. & Lundström, T. S. (2022). A dual-lattice hydrodynamic-thermal MRT-LBM model implemented on GPU for DNS calculations of turbulent thermal flows. International journal of numerical methods for heat & fluid flow, 35(5), 1703-1725
Open this publication in new window or tab >>A dual-lattice hydrodynamic-thermal MRT-LBM model implemented on GPU for DNS calculations of turbulent thermal flows
2022 (English)In: International journal of numerical methods for heat & fluid flow, ISSN 0961-5539, E-ISSN 1758-6585, Vol. 35, no 5, p. 1703-1725Article in journal (Refereed) Published
Abstract [en]

Purpose

The purpose of this paper is to present a fast and bare bones implementation of a numerical method for quickly simulating turbulent thermal flows on GPUs. The work also validates earlier research showing that the lattice Boltzmann method (LBM) method is suitable for complex thermal flows.

Design/methodology/approach

A dual lattice hydrodynamic (D3Q27) thermal (D3Q7) multiple-relaxation time LBM model capable of thermal DNS calculations is implemented in CUDA.FindingsThe model has the same computational performance compared to earlier publications of similar LBM solvers. The solver is validated against three benchmark cases for turbulent thermal flow with available data and is shown to be in excellent agreement.

Originality/value

The combination of a D3Q27 and D3Q7 stencil for a multiple relaxation time -LBM has, to the authors’ knowledge, not been used for simulations of thermal flows. The code is made available in a public repository under a free license.

Place, publisher, year, edition, pages
Emerald Group Publishing Limited, 2022
Keywords
Lattice Boltzmann method, Turbulence, Thermal flows, Direct numerical simulation
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-93178 (URN)10.1108/HFF-06-2022-0339 (DOI)000893826100001 ()2-s2.0-85143219027 (Scopus ID)
Funder
Swedish Research Council, 2017-04390
Note

Validerad;2023;Nivå 2;2023-07-13 (sofila);

This article has previously appeared as a manuscript in a thesis

Available from: 2022-09-22 Created: 2022-09-22 Last updated: 2023-10-14Bibliographically approved
Moosavi, A., Ljung, A.-L. & Lundström, T. S. (2022). Effect of aspect ratio on the thermal performance of confined in-linetube banks: with application for batteries. In: Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson (Ed.), Svenska Mekanikdagar 2022: . Paper presented at Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022. Luleå tekniska universitet
Open this publication in new window or tab >>Effect of aspect ratio on the thermal performance of confined in-linetube banks: with application for batteries
2022 (English)In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
Luleå tekniska universitet, 2022
National Category
Energy Engineering
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-95088 (URN)
Conference
Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022
Available from: 2022-12-30 Created: 2022-12-30 Last updated: 2022-12-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1033-0244

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