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The optimization of the flow field around new vehicle concepts is driven by aerodynamic and thermal demands. Even though aerodynamics and thermodynamics interact, the corresponding design processes are still decoupled. Objective of this study is to include a thermal model into the aerodynamic design process. Thus, thermal concepts can be evaluated at a considerably earlier design stage of new vehicles, resulting in earlier market entry. In a first step, an incompressible CFD code is extended with a passive scalar transport equation for temperature. The next step also accounts for buoyancy effects. The simulated development of the thermal boundary layer is validated on a hot flat plate without pressure gradient. Subsequently, the solvers are validated for a heated block with ground clearance: The flow pattern in the wake and integral heat transfer coefficients are compared to wind tunnel simulations. The main section of this report covers the validation on a full-scale production car.

In the present paper, simulations of a cooling-down process of an automotive disk brake system during a constant drive condition are presented in comparison with experimental data. The simulated condition was chosen because of its considerable sensitivity to the convective heat transfer changes. Performed were simulations of the air flow pattern around a passenger car with fully resolved geometry details including a brake system with pin-shaped brake disks at constant air speed. Conduction and radiation effects were considered by a fully coupled simulation between flow and thermal codes. In CFD, wheel rotation has been taken into account via MRF modeling (= Multiple Reference Frame). A validation of the underlying methodology was recently carried out by comparing characteristic mean values of cooling-down times – which indicate cooling-down behavior – to experimental values obtained in the Thermal Wind Tunnel of Stuttgart University.