Numerical Heat Transfer Studies of Flows Over Concave Surfaces

One of the main objectives of the researchers is to obtain a heat transfer rate enhancement for flows with a minimal increasing in the drag coefficient. The boundary layer over concave surfaces is unstable to centrifugal forces, giving rise to Go¨rtler Vortices. These Vortices create two regions in the spanwise direction, the upwash and downwash regions. The downwash region is responsible to compress the boundary layer in the wall direction, increasing the heat transfer rate. The upwash region does the opposite. In the nonlinear development of the Go¨rtler Vortices it can be observed that the upwash region becomes narrow, and the average heat transfer rate is higher than that for a Blasius boundary layer. In the present work Spatial Direct Numerical Simulations are carried out in order to quantify the heat transfer coefficient of flows over concave surfaces. Three different wavelength values were used to verify the influence of this parameter in the heat transfer rate. The results were obtained for gaseous and liquid media, using Prandtl numbers equal 0.72 and 7.07 for that, respectively. The results show that the heat transfer rate can achieve values close to turbulent boundary layers without increasing too much the drag coefficient.