Stability and mixing of a vertical round buoyant jet in shallow water

Abstract

Discharging heated water through submerged vertical round ports located at the bottom of a receiving water body is a currently used method of waste heat disposal. The prediction of the temperature reduction in the near field of the buoyant jet is a problem of environmental concern. The mechanics of a vertical axisymmetric buoyant jet in shallow water is theoretically and experimentally investigated. Four flow regimes with distinct hydrodynamic properties are discerned in the vicinity of the jet: the buoyant jet region, the surface impingement region, the internal hydraulic jump, and the stratified counterflow region. An analytical framework is formulated for each region. The coupling of the solutions of the four regions yields a prediction of the near field stability as well as the temperature reduction of the buoyant discharge. It is found that the near field of the buoyant jet is stable only for a range of jet densimetric Froude numbers and submergences. A theoretical solution is given for the stability criterion and the dilution of an unstable buoyant jet. A series of experiments were conducted to verify the theory. The experimental results are compared to the theoretical predictions. Good agreement is obtained.