Experimental study of Taylor's hypothesis in a turbulent soap film

An experimental study of Taylor's hypothesis in a quasi-two-dimensional tur bulent soap film is presented. A two-probe laser Doppler velocimeter enable s a nonintrusive simultaneous measurement of the velocity at spatially sepa rated points. Using the cross correlation between a pair of points displace d in both space and time, the velocity coherence is measured to be better t han 90% for scales less than the integral scale. Taylor's hypothesis is con firmed insofar as the lower moments of the longitudinal velocity difference are equal whether measured with or without invoking the hypothesis. A quan titative study of the decorrelation beyond the integral scale is also prese nted. (C) 2000 American Institute of Physics. [S1070-6631(00)02103-6].