Example of a car driving through water
After heavy rain events streets may be flooded and the maximum wading depth of the car can be reached quickly. The wading depth of a car is the distance between the road and the air intake of the engine. Furthermore, even at low velocities it is possible for a bow wave to develop, which increases the risk of water getting into the combustion system. Apart from the above problem, the dynamic and static fluid forces on the chassis parts may be significant.
Computational Fluid Dynamics can provide valuable insight in the flow field around a car (water and air). Especially the fluid forces on the chassis parts due to driving through deep water and the critical water height in the engine bay can be predicted very accurately for different front-end designs and driving velocities.
The video shows the simulation of a generic car driving through water (car model DrivAer © Chair of Aerodynamics and Fluid mechanics, Technical University of Munich).