The numerical computation of near-wall turbulent flow over a steep hill

Abstract

The present work performs a detailed comparison between numerical computations for the flow over a two-dimensional steep hill and some newly obtained laboratory data. Six turbulence models were tested: four eddy-viscosity models ( κ – ε , RNG- ε , κ – ω , SST) and two second-moment models ( SSG– RSM- ε , BSL– RSM- ω ). The experiments were conducted in a water channel and were specially planned such that the large separated flow region that is formed on the lee side of the hill could be well scrutinized. The experimental results include complete profiles of the mean velocity components and of the two-dimensional Reynolds stress tensor and were obtained through the laser Doppler anemometry. A particular concern of this work has been to achieve a detailed experimental and numerical characterization of the near-wall flow region. As such, for most of the measuring stations, at least eight points were located in the viscous sublayer. The work also shows the distribution of wall-shear stress in detail. The ω -equation-based models were observed to perform much better than the ε -equation-based models. The length of separated flow region, mean velocity profiles and wall-shear stress were all reasonably well predicted. The flow properties on the hill top were particularly difficult to describe. The turbulence properties in the reversed flow region were best simulated by the BSL– RSM model.