Search Results

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.

Efforts in aerodynamic optimization of road vehicles have been steadily increasing in recent years, mainly focusing on the reduction of aerodynamic drag. Of a car's total drag, wheels and wheel houses account for approx. 25 percent. Consequently, the flow around automotive wheels has lately been investigated intensively. Previously, the authors studied a treaded, deformable, isolated full-scale tire rotating in contact with the ground in the wind tunnel and using the Lattice-Boltzmann solver Exa PowerFLOW. It was shown that applying a common numerical setup, with velocity boundary condition prescribed on the tread, significant errors were introduced in the simulation. The contact patch separation was exaggerated and the flow field from wind tunnel measurements could not be reproduced. This investigation carries on the work by examining sensitivities and new approaches in the setup.

State-of-the-art aerodynamic research of vehicles often employs strongly simplified car models, such as the Ahmed and the SAE body, to gain general insights. As these models exhibit a high degree of abstraction, the obtained results can only partly be used for the aerodynamic optimization of production vehicles. Aerodynamic research performed on specific vehicles is on the other hand often limited due to their short life span and restricted access. A new realistic generic car model for aerodynamic research - the DrivAer body - is therefore proposed to close this gap. This paper focuses on the development of the model and the first experimental results, namely force and pressure measurements of the different configurations. The experiments were performed in the recently updated Wind Tunnel A of the Institute of Aerodynamics and Fluid Mechanics at the Technische Universität München.