Stratified Flow over Topography: Wave Generation and Boundary Layer Separation

We have performed laboratory experiments to study wave generation over and in the lee of model topography. We have chosen to use periodic, finite-amplitude hills which are representative of the Earth’s major mountain ranges as well as the repetitious topographic features of the ocean floor. The topographic shapes are selected to encompass varying degrees of roughness, from smoothly-varying sinusoidal hills to sharper triangular and rectangular hills. Contrary to linear theory predictions, the (vertical displacement) amplitude of the internal waves directly over the hills is generally much smaller than the hill height. This is because fluid is trapped in the valleys between the hills effectively reducing the amplitude of the hills. Thus the experiments serve to emphasize the importance of boundary layer separation upon internal waves generated by flow over rough topography.