<p>Flow over arrays of cubes is an extensively studied model problem for rough wall turbulent boundary layers. Not only are cube elements notionally representative of the surface roughness encountered in real engineering applications such as urban canopies, but a great deal of richness can still be achieved through simple measures such as changing inter-cube spacing and orientation. While considerable effort has been made in investigating these topologies using DNS and LES, the ability of sublayer-resolved RANS to predict the bulk flow phenomena of these systems is relatively unexplored, especially at high packing densities. Here, RANS simulations are conducted on six different packing densities of cubes in aligned and staggered configurations. The packing densities investigated span from what would classically be defined as isolated up to those in the d-type roughness regime. &nbsp;Three different sublayer-resolved turbulence closure models were tested for each case; a low Reynolds number k-epsilon model, the Menter k-omega SST model, and a Reynolds Stress Model. Comparisons of the velocity fields, secondary flow features, and drag coefficients are made between the RANS results and existing LES and DNS results from the literature. There is a high degree of variability in the performance of the various RANS models, especially in the prediction of the secondary flow features. The Reynolds Stress Model demonstrated the best predictive value in terms of the mean velocity profile as well as drag partition across the range of packing densities.</p>

Modeling of Cube Array Roughness: RANS, LES, and DNS

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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