3D CFD Simulation of a Vehicle Driving in Snow

Abstract

Motor vehicles are designed for different purposes. For the development of motor vehicles it is essential that the vehicles function without problems in winter. For this purpose, winter test drives are carried out in elaborate trials in order to determine, for example, how much snow is deposited on which structural components in the wheel arch. For the tests, ready-to-run vehicles must be available, which are often only available at a late stage of the development process and are usually very expensive to purchase. In this publication, a 3D CFD calculation method is presented. The calculation method is based on a SPH method, with which the snow entry into the wheelhouse is simulated. First, the simulated snow in the form of wet snow is validated on simple experiments. Then, the validated snow parameters are used to calculate the snow entry into the wheelhouse of a real, complex vehicle. In a first step the aerodynamics is neglected and the simulation is focused on purely the snow phase, i.e. a very slow driving speed. In a second step, the influence of airflow on snow input is investigated. Herefore a higher speed of the car is assumed. The results of the snow entry with and without the influence of the airflow field are compared and a discussion is given. Finally the simulation results are validated with real experiments. Herefore an Audi Q7 was tested on an ice field covered with new snow. Different cameras attached to the car have filmed the snow entry into the wheel arch. Important components of the vehicle, like for example the tires, have been 3D scanned in order to set up a simulation where the geometry is almost identical to the tested real car. A comparison of the experimental and numerical results is presented. Overall a CFD setup is presented that is able to simulate wet snow on a complex real car wheel arch geometry.