This paper is concerned with the correction of automotive aerodynamic force coefficient data in the presence of a static pressure gradient imposed by the boundaries of the wind tunnel. The current state-of-the-art approach, introduced by E. Mercker, K. Cooper, and co-workers, has been shown to effectively collapse results that were initially measured in different pressure gradients. However, an operational disadvantage of their approach is that two separate measurements are required, one in the wind tunnel's natural pressure gradient, and another in an alternate, artificially imposed gradient. Both measurements are then combined to produce the corrected result. Although the second measurement may be automated in some circumstances, the method would be more attractive to development engineers and wind tunnel operators alike if the second measurement could be eliminated altogether. In this paper, we use data sets from two different 3/4-open-jet wind tunnels to investigate whether a correlation can be developed that predicts the second measurement, or bypasses it, so that the final corrected result can be estimated with only a single measurement. The analysis shows that this can be done for the drag coefficient with good confidence by choosing from several different correlation models over a surprisingly diverse set of vehicle shapes and sizes (including blockage ratios up to 28 %), although the complexity of the correlation equation increases as larger vehicles are included. Some discussion is also provided on the additional challenges associated with developing similar correlations for front and rear lift.
On using correlations to eliminate the second measurement for pressure gradient corrections
2013
23 Seiten, Bilder, Tabellen
Aufsatz (Konferenz)
Englisch
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