Critical Regimes of Flows with Density Stratification

This study first discusses the analogy between flow in an open channel and either internal or surface currents in large bodies of fluid and shows that the concept of the critical regime is generally applicable to such cases. The critical regime of gravity currents due to density stratification is then examined in terms of both the momentum principle and the somewhat simpler energy principle; contrary to the case of open-channel hydraulics, the two principles result in different flow criteria. In the case of surface currents it is shown that, for constant piezometric or energy level at the surface, the critical regime corresponds to a velocity distribution which reaches a maximum some distance from the surface.