Hypersonic flow predictions using linear and nonlinear turbulence closures

Two- and three-dimensional hypersonic flow cases are computed using linear one-equation closures and a nonlinear two-equation model, where the anisotr opy tensor is modeled as a cubic function of mean strain and vorticity tens ors. The latter is found to excel in predicting bypass transition, whereas the one-equation R-t model is very good at heat-transfer prediction. Both c losures excel in predicting pressure distributions; however, the nonlinear model is found to overpredict heat-transfer. This suggests that in separate d flow regions with simultaneously low mean-flow kinetic energy (and theref ore low strain magnitude) and high temperature gradients, overpredicted lev els of turbulence length scale can lead to rather small errors in the turbu lent shear stress, while at the same time leading to a large overprediction of the turbulent heat fluxes. The simpler one-equation R-t model is theref ore a good candidate for engineering prediction of hypersonic heat-transfer .