Flow Establishment and Initial Entrainment of Heated Water Surface Jets

Mathematical models to predict water temperature distributions resulting from heated water surface discharges usually consider three subregions of the flow field: (a) an outlet region or zone of flow establishment (ZFE), (b) a zone of fully established jet flow, and (c) a far field with mostly passive dispersion. Of these three regions, zone (b) can be treated mathematically most readily using integral techniques; zone (c) requires input specifying mean flow and turbulence of the ambient flow field; and zone (a) depends essentially on the geometry of the outlet and the discharge characteristics in terms of the velocity and temperature of the water. The results of an experimental study dealing with zone (a) are reported. The discharge channel had a rectangular cross section and led into a deep, wide reservoir. The aspect ratio (width-to-depth ratio) of the channel, the volumetric discharge rate, and the discharge temperature were varied. A cross-flow was imposed in some of the experiments. The length of the zone of flow establishment, Xo or So, was measured in terms of mean excess temperature, mean velocity, and turbulence intensity along the trajectory. The length, Xo or So, was related to channel aspect ratio A, outlet densimetric Froude number Fo, and cross-flow-to-jet velocity ratio R. Total volumetric flow rates during flow establishment were established as a function of distance along the jet axis and related to A and Fo. The results are useful either for extension of existing mathematical models of fully developed heated water surface jets or for verification of mathematical models of the zone of flow establishment.Office of Research and Monitoring U.S. Environmental Protection Agenc