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This paper describes the computational technique used to predict flow over and through the front end of vehicles; this scope includes flow over the hood, around air dams, through condensers, radiators, fans, and in the engine compartment. The computational procedure, employed is a finite-difference method for solving time-averaged equations for turbulent flow using the κ-∈ model. A two-dimensional program was modified to add variable-depth cells (in the direction of car width) so that some three-dimensional features could be included. A turbulence model was used which is applicable to rotational and irrotational areas of the flow field. The total system model was calibrated with wind-tunnel data, and various modifications to the vehicle configuration were studied. Results from the predictions were compared with wind-tunnel test data.

In an automotive engine cooling system, the heat rejected to the coolant by the engine and other components is transferred to the air by the radiator. The cooling system engineer must predict the coolant inlet temperature (the top water temperature) for each operating conditions of interest. Computational fluid dynamics (CFD) computer programs have been developed to predict the cooling air flow velocities and temperatures entering the radiator. Radiator effectiveness is measured on a calorimeter with uniform air velocity and temperature entering the radiator. Computer programs have been developed to predict calorimeter performance for new radiators based on experimental data from existing components. In applying the calorimeter performance model to a vehicle, some means must be used to derate the performance slightly based on the non-uniform inlet air velocity and temperature distribution entering the radiator.