Negatively buoyant flow in a diverging channel. I: Flow regimes

Negatively buoyant (plunging) flow entering a horizontal and diverging channel has been studied in the laboratory. Such flow is found at the heads of reservoirs and near effluent sites into lakes. Six flow regimes could be distinguished in the experiments. The flows are similar to nonbuoyant, twodimensional diffuser flow, but negative buoyancy adds several variations. The dependence of the flow regimes on the inflow channel aspect ratio, inflow densimetric Froude number, diffuser half-angle, and channel-to-diffuser transition are presented. The experimental results can be used to predict if and where flow separation will occur and what flow regimes will be present.