Using a free-wake analysis, this study examines several approaches - (i) planar or 'miss-distance' method, (ii) spherical method (a new method developed in this study), (iii) inflow, (iv) blade loads, and (v) blade root loads - for the numerical detection of helicopter blade-vortex interactions (BVIs). The results indicate that all methods other than the spherical method require a high-resolution discretization of the azimuth to detect parallel BVI. Using the spherical method, parallel BVI is detected even on a low-resolution grid (with an azimuthal step size of 4.5 degrees). All the other methods require considerable post-processing including determination of the distorted wake geometry on the high-resolution grid points by interpolation. It is also shown that the vortex core growth parameters being used in some studies result in a vortex that is too diffused, and one that would not produce the impulsive changes in inflow or blade loads, associated with the occurrence of BVI. While choice of the vortex core radius or growth law is important for BVI detection based on inflow or blade loads, it does not influence detection using the planar and spherical methods.
A critical evaluation of various approaches for the numerical detection of helicopter blade-vortex interactions
Numerisches Verfahren zur Ermittlung der Interaktion zwischen den Rotorblättern eines Hubschraubers und den von ihnen erzeugten Wirbeln
Journal of the American Helicopter Society ; 45 , 3 ; 179-190
2000
12 Seiten, 22 Bilder, 19 Quellen
Aufsatz (Zeitschrift)
Englisch
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