Results from wind tunnel experiments at ENFLO (University of Surrey, UK) on flow over a two-dimensional hill are compared with simulations using the Met Office BLASIUS model. Both neutral and stably stratified cases are considered. Both a shallow and a steep hill are used, with the steep hill giving rise to separation and recirculation while the flow over the shallow hill remains attached. Measurements of velocity, temperature and surface pressure from the wind tunnel are compared with the model predictions.

The importance of the turbulence scheme in modelling these flows is investigated. Initially a 1.5 order turbulence closure scheme is used to model these flows. The effect of a second order closure is also investigated in the neutral case in an attempt to better model and understand the shear stresses observed above the hill in the windtunnel and the occurence of flow separation.

Finally some results are shown for simulations with both hills present to investigate the effect of the flow induced by the upwind hill on the flow over the downwind hill. Such interactions can cause resonance effects under certain conditions with important effects on local weather conditions in the lee of the hills.