Simulation of Rear and Body Side Vehicle Soiling by Road Sprays Using Transient Particle Tracking

Numerical simulations have proven to be effective tools for the aerodynamic design of vehicles, helping to reduce drag, improve cooling flows, and balance aerodynamic lift. Aeroacoustic simulations can also be performed; these can give guidance on how design changes may affect the noise level within the cabin. However, later in the development process it may be discovered that soiling management issues, for example, necessitate design changes. These may have adverse consequences for noise or require extra expense in the form of technological counter-measures (i.e. hydrophobic glass).Performing soiling simulations can allow these potential issues to be addressed earlier in the design process. One of the areas where simulation can be particularly useful is in the prediction of soiling due to wheel spray. Our previous work on this topic examined the uses of pre-calculated flow fields and particle ‘hit points’ to predict dirt coverage. 1In this study, the advantages of using fully transient particle tracking along with a film model for the simulation of wheel spray are investigated. These include the elimination of ad hoc particle emitters (used to account for dripping), a more accurate splash model, and the ability to account for fluid particle interaction. Results are compared to both wind tunnel and track test data, along with those of a previous study which used a pre-calculated flow field methodology on the same vehicle. The results for the transient solver show improved side and rear surface coverage. These improvements are credited to more accurate transient tracking of particle trajectories, the inclusion of more realistic physics and the ability to simulate a far larger number of particles.