Analysis of Unsteady Aerodynamics of a Car Model with Radiator in Dynamic Pitching Motion Using LS-DYNA

This paper describes the numerical analysis of unsteady aerodynamics of a radiator mounted car model in dynamic pitching motion using LS-DYNA ICFD solver. Large-Eddy simulations with ALE method and porous media modeling were performed to clarify the unsteady aerodynamic forces acting on cars with engine compartment in dynamic motion. The forced sinusoidal pitching oscillation was imposed on the 1/4 scaled car model. The model was based on a real production car and it was simplified by smoothing its surface. The engine compartment contained a radiator model (i.e., porous media). The cooling-air inlet and outlets were located in front end of the model, on the floor of the model and on the side wall of the front wheel houses respectively. In the previous report [1], similar simulations were performed to clarify the unsteady aerodynamic forces acting on a simplified car model (without engine compartment). As a result of previous analysis, it was revealed that the unsteady aerodynamic effects are mostly due to the changes of the flow structures behind the front tires owing to volume shrinking or expanding of front wheel house with car dynamic motion. However, the cooling-air flow passing through radiator and front wheel house was not considered. In this paper, differences between the unsteady aerodynamic forces acting on the car model with the engine compartment in the dynamic pitching motion and those on the model without engine compartment were investigated. Furthermore, the mechanisms that the differences occur (i.e., cooling-air interference) were mainly discussed. The results showed remarkable differences especially in the lift force during nose-down motion. As a result of this analysis, it was revealed that these differences were mostly due to the changes of the flow structures around front wheel house caused by exiting the cooling-air flow through front wheel house.