Integral Model for Plane Buoyant Jets and Spreading-Intrusion Layers in Linearly Stratified Fluids

The mean flow and mixing properties of vertical plane turbulent buoyant jets in stagnant and linearly stratified environments are predicted using an integral model. This model is coupled with an original model to predict the geometric and hydraulic characteristics of the spreading and intrusion layers formed. The model is based on the spreading concept with Gaussian similarity profiles for the mean axial velocity and mean concentration because it derives a consistent centerline variation of the entrainment coefficient while affected by the stratification. This work introduces the stratification number defined as the ratio of initial fluxes of momentum/buoyancy times the stratification frequency. Novelties include finding that the location of maximum entrainment coefficient corresponds to the lower boundary of the intrusion layer, and the definition and calculation of the nominal characteristic cross section through which the buoyant jet flow begins to spread laterally. The coupled system of models considered the additional fluid entrained from the upper-layer cap. The model predictions are successfully compared with available measurements, verifying the reliability of the coupled system in engineering applications.