Turbulent Flow over Cars


, Isfahan University of Technology


In this paper the flow behaviour over a number of car bodies is studied. For this purpose the unsteady 2-D incompressible Navier-Stokes equations have been applied. After averaging and nondimensionalizing the equations, the system of equations has been transformed from the Cartesian (x-y) coordinates to a body fitted generalized (-) coordinate. As the flow is incompressible, the density in the continuity equation will disappear and thus the coupling between the continuity and the momentum equations will be lost. To resume the missing coupling between the aforementioned equations an artificial state equation is introduced. This artificial state equation will couple the continuity and the momentum equations via pressure. For turbulence simulation Jones & Launders Low Reynolds turbulence model was employed. By means of an implicit method, the system of five equations are solved. From the flow field solution, the drag force on car geometries are predicted and the results are compared to the drag force calculated from experimental correlations. Agreement is fare enough i.e. within 90 percent of accuracy.