An improved method of analysis was developed to correct for the effects of the inherent aperiodicity exhibited by rotor blade tip vortices that were measured using digital particle image velocimetry (DPIV). The use of a helicity-based correction technique to collocate the centers of tip vortices was shown to provide the most accurate and consistent results for all three components of flow velocity. A statistical analysis was also performed to evaluate the minimum number of instantaneous DPIV velocity maps required to achieve convergence in the estimation of the vortex flow characteristics. A detailed examination of the measured data set showed a skewed distribution, suggesting the median over the mean as a better choice for estimating the various flow characteristics of tip vortices. In addition, the vortex core was found to be nonaxisymmetric, showing an elliptical shape at all wake ages.
Digital particle image velocimetry measurements of tip vortex characteristics using an improved aperiodicity correction
Digitale PIV-Geschwindigkeitsmessungen zur Charakteristik von Wirbeln an Schaufelspitzen mit verbesserter aperiodischer Korrektur
Journal of the American Helicopter Society ; 54 , 1 ; 012004/1-012004/13
2009
13 Seiten, 20 Bilder, 1 Tabelle, 34 Quellen
Article (Journal)
English
Aperiodicity Correction for Rotor Tip Vortex Measurements
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