Historically, car companies that are developing new models tend to bring indoor most of the testing activities. In particular, the aerodynamic and aeroacoustic work is carried out by using wind tunnels that are supposed to reproduce, at the best possible level, the conditions that a car experiences on the road. A Turbulence Generation System (TGS) specifically designed to reproduce in the wind tunnel a flow condition more similar to that found by the cars on the road, has been in operation in Pininfarina since the beginning of 2003. Regarding the system itself, it works pretty well: it can simulate a number of realistic turbulent flow conditions, similar to those that a car can find when it moves on the road. In particular it is able to produce a Turbulence Length Scale (TLS) of large size, never produced up to now in other full scale automotive wind tunnels. Furthermore, the tests made up to now have shown that the system has a strong potential for further improvement. The work that is now in progress has the aim to increase the range of possible flow simulations. Most of the hardware will be kept as it is, however new modes of operation will be explored. Regarding the results of the tests made on various vehicles in condition of turbulent flow, a lot of new interesting information has been collected. On the aeroacoustics side, it can be stated that: The noise quality is different; the perceived noise is subjectively more similar to that heard on the road. Low frequency noise is usually increased, high frequency noise is about the same (on average), it can be lower or higher depending on the specific car. Some tones that are well perceived in the low turbulence flow may disappear or reduce in presence of high turbulence flow. That is valid for both the interior noise measured by acoustic heads and the exterior noise measured by acoustic mirrors. The Articulation Index and the various psychoacoustics parameter, all show some deterioration, mainly at the lower frequencies, in presence of a turbulent flow. In reality, the main conclusion is that the simulation, in a full scale automotive wind tunnel, of flows having high turbulence intensity and TLS of large size, brings to: - a new area of testing, getting closer to the 'road condition', and - a new area of knowledge, that is at present largely unknown. And that Is the challenge for our future activities in aerodynamics and aeroacoustics.
Generation of a controlled turbulent flow in an automotive wind tunnel and its effect on car aerodynamics and aeroacoustics
Erzeugung einer geregelten turbulenten Strömung in einem Automobil-Windkanal und der Einfluß auf die Fahrzeugaerodynamik und Aeroakustik
2004
27 Seiten, 42 Bilder, 1 Tabelle, 46 Quellen
Conference paper
English
Automotive engineering | 2004
|Aerodynamics and Aeroacoustics
Tema Archive | 2007
|British Library Conference Proceedings | 2003
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