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°, Re 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 ≤ 10°) and lattice-like ( α ≥ 15°), fundamentally altering the friction factor. Furthermore, the maximum friction factor obtained in the creeping regime occurred at α = 25°, whereas in the inertial regime, this occurred at α = 60°. 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. • Pressure drop systematically quantified across 19 rotation angles. • Wetted surface area governs drag in non-spherical beds. • Two analytical models predict permeability of complex geometries. • Diameter ratio and tortuosity reliably classify packed-bed flow regimes.