Flow and Heat Transfer over Rough Surfaces: Usefulness of 2-D Roughness-Resolved Simulations

Computations, based on the Fluent-UNS code with second-order upwind differencing and the realizable k-e model, were performed to study the flow and heat transfer over two-dimensional (2-D) roughness geometries that resolve the details of the jagged surface. Parameters studied include height of approaching boundary layer to average roughness height (3.0 to 30) for the same rough surface and eight different rough surfaces with the same approaching boundary layer in which the average roughness height, rms, skewness, and kurtosis of the roughness vary in the ranges of 0.748 to 1.480, 0.991 to 1.709, -1.509 to 0.356, and 1.927 to 3.136, respectively. Results are presented for the contributions to the friction coefficient from shear and from pressure – locally and averaged over the entire rough surface. Also presented are the computed flow fields and the averaged Stanton numbers for all rough surfaces studied. Results obtained by the 2-D roughness-resolved simulations were compared with experimental data.