In the course of the progressive electrification of the drive train in automotive vehicles and the associated increased relocation of the drive units to the rear of the vehicle as well as an increasing cladding of the vehicle underbody for aerodynamic optimization, the requirement for a realistic simulation of the aero-thermal field and in particular of the temperatures of the components in the rear of the vehicle is becoming increasingly important. In addition, the ever shorter product cycles demand ever shorter development times, which is why vehicle development is increasingly being shifted from the road to the test bench. For this reason, the aim of this work was to identify and quantify the individual factors which could cause a possible falsification of the vehicle bypass and the heat exchange between the vehicle and the ambient air in the wind tunnel. Subsequently, on the basis of a potential theoretical modelling of a simplified wind tunnel flow, possible measures for compensating the influence of the collector on the vehicle flow were developed and investigated simulatively using stationary CFD methods and experimentally in the wind tunnel. Thereby, three different vehicle geometries were considered. It was shown that the approach of compensating the wind-tunnel induced interferences by the arrangement and alignment of vertical wing profiles behind the vehicle does indeed result in a desired change of the vehicle rear flow and the convective heat transfer in the rear area. However, it was not possible to derive a universally valid correlation between the wing position or orientation, which is why this approach appears to be less practicable in wind tunnel-supported vehicle development due to the strong dependency on the vehicle geometry. In the course of the progressive electrification of the powertrain in automotive vehicles and the associated increased relocation of the drive units to the rear of the vehicle as well as increasing cladding of the vehicle underbody for aerodynamic optimization, the requirement for a realistic simulation of the aero-thermal field and in particular of the temperatures of the components in the rear of the vehicle is increasingly coming into focus. In addition, the ever shorter product cycles require ever shorter development times, which is why vehicle development is increasingly being shifted fromthe road to testing facilities such as climatic wind tunnels. These climatic wind tunnels are used in the development process because they can be used to simulate the temperature development of individual vehicle components under the influence of various external environmental influences, such as altitude or humidity. However, in comparison with a road test, this inevitably results in systematic deviations of the vehicle flow around and through the vehicle as well as the temperature field. For this reason, the aim of this work was to identify and quantify numerically and experimentally the individual factors that cause possible systematic deviations of the vehicle flow and the heat exchange between the vehicle and the ambient air in the wind tunnel. Based on a potentialtheoretical modeling of a simplified wind tunnel flow, various measures for compensating the influence of the wind tunnel geometry including the collector on the vehicle flow were developed and validated simulatively using stationary CFD methods and experimentally via temperature and pressuremeasurements in the wind tunnel. In each case, three different vehicle geometries, which differ greatly in their aerodynamic performance, were considered. It was shown that the wind tunnel-induced interferences, which lead to the systematic deviations of the wind tunnel flow and the temperature distribution in and on the vehicle, can be compensated by the arrangement and alignment of vertical wing profiles behind the vehicle. Thus, it could be shown that by modifying the vehicle rear flow and the convective heat transfer in the rear area by means of flow control measures, a very good agreement of the flow and temperature conditions between road and wind tunnel can be realized. This will allow reliable analyses to be carried out in the wind tunnel in the future.    «

In the course of the progressive electrification of the drive train in automotive vehicles and the associated increased relocation of the drive units to the rear of the vehicle as well as an increasing cladding of the vehicle underbody for aerodynamic optimization, the requirement for a realistic simulation of the aero-thermal field and in particular of the temperatures of the components in the rear of the vehicle is becoming increasingly important. In addition, the ever shorter product cycles d...    »