Wind and stream flow induced reaeration

Reaeration in combined wind/stream driven flows was experimentally studied in a laboratory wind-water tunnel. Wind velocities, stream flow properties, and oxygen transfer rates were measured under a variety of cocurrent and countercurrent flow conditions. For pure open channel flows and pure wind-driven flows, respectively, the results of oxygen transfer measurement can be scaled by the simple forcing parameters and show good agreement with other laboratory studies. For wind/stream combined flows, the transfer velocity depends on the stream flow condition and wind shear velocity. Based on the magnitude of the bottom-shear induced transfer and the wind-shear induced transfer velocity, a criterion was proposed to determine the dominant mechanism for gas transfer in combined wind/stream driven flows. A simple additive model is developed for the reaeration coefficient in combined wind and stream flow-influenced environments. Also, the effects of tidal flow on reaeration in tidal estuaries are briefly discussed.