Search Results

Both the external and internal flows of cars are simulated simultaneously. A third-order upwind-difference scheme is used in these simulations. Computational grids are generated by a multi-block transformation and a trans-finite method. Engine compartments are modeled by grid systems but the heat exchanger is simulated as a pressure loss proportional to the dynamic pressure of the flow passing through it. First, the flow for a very simple test model with no wheels and nothing in its engine compartment is simulated and compared with experimental results in order to validate a simulation method for the engine compartment. Pressure distributions on the inner surfaces agree very well with measured values, while pressure distributions on the external surfaces show reasonable agreement except for the roof end and the leading edge of the floor. The predicted drag coefficient is 7% larger than the experimental value. This method is next applied to a prototype car.

Numerical simulation of two-dimensional and three-dimensional air flow in automobile passenger compartments is described. The flow can be expressed by means of an incompressible Navier-Stokes equation for a narrow temperature range. The results were represented visually using animation and a color graphics system. The two-dimensional simulation showed that heat ansfer takes place chiefly by convection in vortices, and that the effects of heat transfer are minimal. In the three-dimensional analysis, shading was used to show the shape inside the compartment, and instantaneous stream lines and temperature distribution were depicted. The three-dimensional stream lines swirl upward at the front seat, and do not reach the back seat. The results gained from this study show that present theoretical flow analysis methods are close to being perfected. Further advances will require additional refinement of supercomputers and graphic engineering workstations.