Laboratory study on the two‐dimensional flows of stratified fluids over barriers

This paper describes an experimental study of a stratified fluid of finite depth flowing over obstacles which induce flow seperation and turbulence on the lee side, in which the inviscid model is no longer useful. Various properties of the flow field, such as the development of lee waves behind the obstacle, the blocking effect upstream, the effect of viscosity, and in particular the criterion for the onset of gravitational instability in the lee‐wave field, are observed and analyzed. The results show that lee waves produced by obstacles in a stratified flow depend on the internal Froude number, the ratio of the height of obstacles to the channel depth, the ratio of the height to the half width of obstacles, and the Reynolds number of the flow. Therefore, it can be found that the existence of upstream influence and the flow seperation induced by the obstacle have great effect in some flow conditions on the development of the lee‐wave field.