Numerical simulation of thermal discharges in crossflow

A three-dimensional computational fluid dynamic (CFD) model is developed for resolving the turbulent initial mixing of thermal discharges. To handle the huge difference of length scales between actual flow domain and relatively tiny diffuser, we employ the domain-decomposition approach with multi-level overset grids. A subgrid-scale eddy viscosity model with a simple Richardson-number correction for buoyancy effects is used for the turbulence closure. The governing equations are solved with a second-order-accurate, finite-volume, artificial compressibility approach. The evaluation test using experimental measurements for the development of thermally stratified shear flows in a laboratory channel shows that the CFD model works well in simulation of shear flows dominated by the buoyancy. The CFD model is applied for resolving the turbulent initial mixing of thermal discharges loaded from both a single-port diffuser in an artificial channel. The results demonstrate that the CFD model provides reasonable and satisfactory predictions of turbulent initial mixing of buoyant jets in different cross flow conditions and appears to well capture main features of the initial mixing controlled by the interplay of the ambient flow and thermal discharges.