Method development for the use of Smoothed-particle hydrodynamics simulations for vehicle soiling analysis

Sammanfattning: An increasing amount of sensors is being placed in cars in order to monitor their vicinities, which performance is highly dependant on the driving conditions, in which weather has a big role, and thus water contamination is a topic that will increase its importance in the future of the car industry. One of these sources of contamination is self-soiling: how cars get dirty because of their own tires. Thus, historically speaking this phenomena has been treated computationally by the use of droplet rakes in the tires which do not consider how this water has been picked up, or how it detaches from the tire itself. In this thesis the method to apply results obtained from Smoothed-particle Hydrodynamics (SPH) simulations of the tire droplet adhesion and release, to vehicle soiling simulations in order to improve the accuracy of these studies has been developed. In order to develop the method, first the SPH simulation data has been treated by filtering it according to the droplet location and the tire characteristics which has lead to the development of a geometrical and a kinematical filter for the data set.  Afterwards, the results for the coarsest data set have been applied in the external aerodynamics simulation of a DrivAer bluff car model, as a proof-of-concept simulation, in which a Lagrangian Multiphase + Fluid film simulation has been developed for three different regimes: an unsteady injection with data extracted from the SPH simulations (USPH), a steady injection (SSPH) with the same data set origin and eventually a variable mass flow rake simulation (VMFR), with particles being injected in a rake pattern following the classic method which has been the most extended method in industry and academia to simulate vehicle soiling. These three simulations have been compared among each other so that the main similarities and differences are presented in the report. It has been seen that the injection pattern of USPH and SSPH is similar compared to the classic VMFR simulation, which differs notably both in injection and wake. Moreover, the pattern of fluid film generated in the sides of the car is also similar in both USPH and SSPH, being more intense in the former. Nevertheless, the results from VMFR indicate that the pattern covers more of the side of the car, even though the intensity of the film generated is lower compared to the SPH cases.