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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 centered 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 ["Flow field characterisation of gaseous flow in a packed bed by particle image velocimetry," Transp. Porous Media 150, 307 (2023)] using particle image velocimetry. The numerical results compare favorably with the measurements both inside and above the bed. The effect of differences arising between the physical and numerical configurations is thoroughly discussed alongside the impact of meshing strategy on the accuracy of the predictions. [ABSTRACT FROM AUTHOR]

For turbulent flows in porous media, it is often assumed that the irregularity of the matrix would not affect the macroscopic, double‐averaged (in time and space), parameters of turbulence. Hence, to improve currently used modelling techniques, the ongoing efforts of the community are focused on performing high‐fidelity, scale‐resolving simulations of flows in regular, periodically repeating porous structures. This approach allows for minimizing still large computational cost, however, it assumes that results obtained from those geometries are generalizable to more disordered configurations. We investigate this assumption numerically using large‐eddy simulation and analyse the influence of the irregularity of the porous structure on turbulent characteristics in a fully turbulent flow in a channel half‐filled with porous medium. The flow statistics are examined and compared between four simulations, a reference channel with regular three‐dimensional porous matrix consisting of an array of cubes and three similar geometries created from randomly perturbing the positions of the cubes, with increasing mean value of cube displacement. We study double‐averaged flow properties, the distributions of double‐averaged Reynolds stress tensor, including the anisotropy of macroscopic turbulence and the drag force induced by the flow in the porous region of the channel. The results confirm the idea that the averaged characteristics, including the anisotropy of the stress tensor and the drag force, are not greatly influenced by the moderate perturbation to the geometry of the porous matrix. Additionally, the macroscopic turbulence seems to exhibit a high degree of anisotropy in the porous region and the adjacent boundary layer, suggesting that second‐order closure could be an adequate modelling choice for such flows. [ABSTRACT FROM AUTHOR]

The framework of inner product norm preserving relaxation Runge--Kutta methods [D. I. Ketcheson, SIAM J. Numer. Anal., 57 (2019), pp. 2850--2870] is extended to general convex quantities. Conservation, dissipation, or other solution properties with respect to any convex functional are enforced by the addition of a relaxation parameter that multiplies the Runge--Kutta update at each step. Moreover, other desirable stability (such as strong stability preservation) and efficiency (such as low storage requirements) properties are preserved. The technique can be applied to both explicit and implicit Runge--Kutta methods and requires only a small modification to existing implementations. The computational cost at each step is the solution of one additional scalar algebraic equation for which a good initial guess is available. The effectiveness of this approach is proved analytically and demonstrated in several numerical examples, including applications to high order entropy-conservative and entropy-stable semidiscretizations on unstructured grids for the compressible Euler and Navier--Stokes equations. [ABSTRACT FROM AUTHOR]