Felix Wittmeier

Design and First Test of the New Synchronous 200 Hz System for Unsteady Pressure Field Measurement

This paper introduces an innovative pressure measurement system for unsteady flow measurement. Unsteady flow is currently one of the hot topics of road vehicles aerodynamics and an inexpensive, simple-to-use tool for its investigation has long been missing. Conventional pressure measurement systems with centralized pressure scanners and long tubings do not satisfy the needs of unsteady phenomena. An approach of miniature MEMS pressure sensors is used instead, whereby the sensors are installed directly on the surface of the body under investigation. This concept not only enables the possibility of unsteady flow measurement but also offers a fast and reliable method of pressure field investigation. Finally, the measurement system was aimed at the specific needs of road vehicle productive testing and provides an effective tool capable of rapid experiment preparation, reliable measurement and simple post-processing.

Classification of aerodynamic tyre characteristics

The geometric shape of the tyres can have a large influence on the aerodynamic drag of a passenger car as it has been shown already in different publications. However, so far it is not possible to quantify the aerodynamic characteristics of a tyre without measuring it mounted on a vehicle in a wind tunnel and comparing it to other tyres. For this reason a research project at the Institute for Internal Combustion Engines and Automotive Engineering at the University of Stuttgart (IVK) was launched with the intention of categorising the aerodynamic characteristics of passenger car tyres.

The influence of wheel and tire aerodynamics in WLTP

The geometric shape of passenger car wheels can have a large influence on the aerodynamic drag of a vehicle as it has been shown already in different publications. In combination, tire and rim cause approximately 25% of the overall drag. Until now, the challenge for aerodynamicists is to find the rim / tire combination with the best aerodynamic characteristics, which then is used for the official cD-value of the vehicle and for the determination of fuel consumption according to NEFZ regulations.

Investigation of Time-Resolved Nozzle Interference Effects

Automotive wind tunnels still see an increasing significance in the vehicle development process. Nevertheless, the flow topology in the test sections of open jet wind tunnels is not yet understood completely. A large source for transient structures is the shear layer developing between the high velocity nozzle flow and the calmly air in the plenum.