Virtual Product Development

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Simulation of inherent and external vehicle soiling

At present, FluiDyna is processing one of the most challenging tasks in the automobile industry sector - the simulation of inherent and external soiling of vehicles.

FluiDyna was fully entrusted with carrying out the work on this project by German-based AiF Projekt GmbH. Since 2010, AiF Projekt GmbH has been a subsidiary of the German Federation of Industrial Research Associations "Otto von Guericke e. V." (AiF). The organization is the patron of the PRO INNO II Programme ("PROgramme to foster the INNOvative capacity of small and medium-sized enterprises"), supporting R&D projects.

The simulation of fluid flows around real vehicle geometries is one of the main fields of application within both numerical fluid mechanics and the closely correlating Finite Volume Method (FVM). These days, the requirements of car manufacturers are becoming more and more complex. Besides pure single-phase flow simulation, their demands also require two-phase and multi-phase flows.

Within two-phase and multi-phase flows, vehicle soiling represents an important area of application. Apart from not being aesthetically pleasing, vehicle soiling has a great impact on passive safety issues which is even more important.

When driving on wet roads, water drops and dirt particles are swirled up. These polluted water drops hit almost every part of a vehicle. When water drops adhere to the side windows, windscreen, rear window and side mirrors, there is a risk factor that should not be underestimated. Actually, while front and rear windows may be wiped and cleaned immediately, it is impossible to remove any soiling on side windows and mirrors promptly.

What is most dangerous is any kind of soiling within the visual field of a vehicle's front side windows: Firstly, soiling of the side windows themselves, and secondly, soiling due to water drops and dirt particles that have accumulated on the side mirrors.
The driver's view in his vehicle's rear-view mirrors is worsened considerably. This is why, for instance, other road users who are moving alongside may easily be overlooked. In addition, traffic behind may be seen only to a limited extent or even not at all through the side mirrors.

Especially in the winter months these circumstances represent huge safety risks. Moreover, the water drops become touch dry. A thin salt film remains on the vehicle's surface. Particularly in winter, the sun's angle of incidence is low and may dazzle the driver, posing just another threat to traffic safety.

This is why minimizing a vehicle's inherent and external soiling is vital. In order to reach this goal, specific know-how about the fouling behaviour of individual vehicle models is essential.

To acquire this knowledge, the automobile industry nowadays mainly applies experimental methods. However, there is one major disadvantage: Indications which might help modify and optimize vehicle fouling tendencies can only be seen at a very late stage of vehicle development.

Getting data on vehicle soiling by applying numerical simulation methods is a reasonable alternative. It enables involving early-emerging parameters on how to avoid vehicle soiling in the early stages of the virtual product development process.

It goes without saying that this method offers a high potential for saving cost and time.