The effect of downstream control on the stability and mixing of an axisymmetric turbulent heated jet discharging vertically into shallow water is studied using the buoyancy extended k - ε model. The steady axisymmetric turbulent flow, temperature and turbulence fields are computed using the finite volume method on a high resolution grid. The numerical predictions show that the near field flow is governed by the discharge densimetric Froude number F_o and the depth to jet diameter ratio H/D, regardless of downstream control - provided that the channel length exceeds about 6H. A radial internal jump always exists beyond the surface impingement region, with a three to sixfold increase in dilution across the jump. The predicted stability category, velocity and temperature fields are well-supported by experiments.
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