Entrainment at thin stratified interfaces: The effects of Schmidt, Richardson, and Reynolds numbers

A new model is proposed for the entrainment at stratified interfaces. In it, the effects of Schmidt, Richardson, and Reynolds numbers are explicitly addressed. There are five regimes; entrainment is controlled by a different process in each. For example, a central assumption in region II is that eddies must make a complete rotation to be directly responsible for entrainment. Therefore, in stratified flow, the eddy scale is defined by the criterion that its Richardson number Ri is equal to unity. This contrasts with unstratified flows, where the largest eddies, unconstrained by buoyancy, engulf and entrain. These results are in accord with the observations, and suggest how laboratory experiments in water may relate to the atmosphere and to the oceans.