Dissimilarity of Turbulent Fluxes of Momentum and Heat in Perturbed Turbulent Flows

Abstract

The dissimilarity between the Reynolds stresses and the heat fluxes in perturbed turbulent channel and plane Couette flows was studied using direct numerical simulation. The results demonstrate that the majority of the dissimilarity was due to the difference between the wallnormal fluxes, while the difference between the streamwise fluxes was lower. The main causes for the dissimilarity were the production terms, followed by the velocitypressure interaction terms. Further insights into the importance of the velocitypressure interaction in the origin of the dissimilarity are provided using twopoint correlation. Furthermore, an octant conditional averaged dataset reveals that not only the wallnormal heat flux but also the streamwise heat flux is strongly related to the wallnormal gradient of the mean temperature. A simple Reynoldsaveraged Navier–Stokes (RANS) heat flux model is proposed as a function of the Reynolds stresses. A comparison of the direct numerical simulation data with an “a prioriâ€‌ prediction suggests that this simple model performs reasonably well.