Numerical simulation of aerodynamics for vehicle development is used to meet a wide range of performance targets, including aerodynamic drag for fuel efficiency, cooling flow rates, and aerodynamic lift for vehicle handling. The aerodynamic flow field can also be used to compute the advection of small particles such as water droplets, dust, dirt, sand, etc., released into the flow domain, including the effects of mass, gravity, and the forces acting on the particles by the airflow. Previous efforts in this topic have considered the water sprays ejected by rotating wheels when driving on a wet road. The road spray carries dirt particles and can obscure the side and rear glazing. In this study, road sprays are considered in which the effects of additional water droplets resulting from splashing and dripping of particles from the wheel house and rear under body are added to help understand the patterns of dirt film accumulation on the side glass and rear glass. Results are compared to experimental photographs for both a sedan and an SUV tested using luminescent dye in a wind-tunnel as well as in road testing. Results show that the addition of splashing and dripping particles increases the impingement of particles on the surface and provides excellent correlation to the experimental data. This allows use of simulation for identifying problems and potential solutions for upper body soiling issues.
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