An experimental and numerical study on the flow over two-dimensional hills

An experimental and numerical investigation on the flow over two-dimensional hilly terrain is presented. Experiments for single hills and continous double hills are performed in a boundary-layer wind tunnel, and mean velocity profiles, turbulence characteristics, and surface pressure distributions are measured. The numerical model developed for the present work is based on the finite-volume-method and the SIMPLEC algorithm with a non-orthogonal body-fitted grid system. Several turbulence models are tested for the validation of the prediction accuracy in separated flow cases. Comparisons of the mean velocity profiles and surface pressure distributions between the numerical predictions and the measurements show good agreement. The linear theory provides generally good prediction of speed-up characteristics at the hill top for the hill slope of 0.3, which is defined as the ratio of the hill height to the base length at the upwind mid-height of the hill. Flow separation occurs in the hill slope of 0.5, and the measured reattachment points are compared with the numerical prediction. The low-Reynolds-number model with an orthogonal grid is found to predict the separated flow better than the other turbulence models.