arXiv subjects

Wojciech Sadowski

Publications and source records attributed to Wojciech Sadowski.

4 recordsLinked to original sources

arXiv2026

Influence of Prandtl number on heat transfer over a permeable wall

The work considers a fully turbulent flow with heat transfer in a channel half-filled with an array of cubes based on the work of Breugem and Boersma (2005) and Chandesris et al. (2013), at $\mathrm{Re}_\mathrm{bulk} = 5485$ and three different Prandtl numbers, $\mathrm{Pr} = 0.71, 0.1, 0.05$. The temperature is modelled as a passive scalar and two different boundary condition configurations are simulated. The influence of the Prandtl number on the mean temperature, its variance and the terms of the temperature budget is highlighted, including the analysis of the distribution and relative importance of the turbulent heat transfer, molecular diffusion, tortuosity and Brinkman terms near the porous-fluid interface. The latter two has been found to be insignificant for the highest $\mathrm{Pr}$. A set of terms, typically neglected during the upscaling procedure (related to the Taylor expansion of the filtered variables), is analysed for the first time for the turbulent heat transfer at the porous-fluid interface, and are found to be significant at low $\mathrm{Pr}$. The upscaled fields are evaluated with three different kernels forming cellular average, linear (i.e., tent kernel), quadratic and cubic, and the influence of the chosen filter is additionally studied.

physics.flu-dyn↗

arXiv2026

Low Reynolds number flow in a packed bed of rotated bars

The present study focuses on the gas flow through an experiment-scale modular packed bed reactor consisting of square bars, arranged in layers. Each layer is rotated by $30^\circ$ resulting in a complex shape of the void spaces between the bars. Particle Image Velocimetry measurement results inside and on top of the studied system are presented for particle-based Reynolds numbers of 100 and 200, and used as validation data for two sets of particle-resolved numerical simulations, using boundary conforming meshing strategy and treating the solid boundaries via the blocked-off method. The flow inside the bed is largely independent from the Reynolds number and seems to be determined by the geometry of the void spaces. The flow in the freeboard is dominated by the presence of slowly dissipating jets downstream of the bed, which are characterized by unsteady oscillations at the higher Reynolds number. The numerical results obtained with both methods are in good agreement with the measurements, both inside and above the bed. However, stronger deviations between the results can be observed in the freeboard and can be traced to numerical properties of the current simulation approaches.

physics.flu-dyn↗

arXiv2026

Modelling of pressure drop in periodic square-bar packed beds

Understanding fluid flow through porous media with complex geometries is essential for improving the design and operation of packed-bed reactors. Most existing studies focus on spherical packings, having as a consequence that accurate models for irregular interstitial geometries are scarce. In this study, we numerically investigated the flow through a set of packed-bed geometries consisting of square bars stacked on top of each other and arranged in disk-shaped modules. Rotation of each module allows the generation of a variety of geometrical configurations at Reynolds numbers of up to 200 (based on the bar size). Simulations were carried out using the open-source solver OpenFOAM. Selected cases (e.g., $α= 30^\circ$, $\mathrm{Re}_\mathrm{p} = 100, 200$) were compared against Particle Image Velocimetry measurements. Results reveal that, based on the relative rotation angle, the realized geometries can be classified as channel-like ($α\leq 10^\circ$) and lattice-like ($α\geq 15^\circ$), fundamentally altering the friction factor. Furthermore, the maximum friction factor obtained in the creeping regime occurred at $α= 25^\circ$, whereas in the inertial regime, this occurred at $α= 60^\circ$. The module-equivalent diameter, based on the angle-dependent wetted surface area, collapses the friction factor onto the Ergun correlation and yields good permeability predictions for the lattice-like geometries.

physics.flu-dyn↗

arXiv2023

High-resolution measurements and simulations of the flow through a packed bed and its freeboard region

The present study focuses on the assessment of the performance of a Finite Volume Method based, particle-resolved simulation approach to predict the flow through a model packed-bed consisting of 21 layers of spheres arranged in the body centred cubic packing. The unsteady flow developing in the freeboard is also considered. Two highly-resolved large eddy simulation were preformed, for two Reynolds numbers, 300 and 500, based on the particle diameter, employing a polyhedral, boundary-conforming mesh. The geometry and the flow conditions are set to reproduce the flow conditions investigated in the experiment carried out by Velten and Zähringer using Particle Image Velocimetry. The numerical results compare favourably with the measurements both inside and above the bed. The effect of differences arising between the physical and numerical configurations are thoroughly discussed alongside the impact of meshing strategy on the accuracy of the predictions.

physics.flu-dyn↗