Experimental study on the generation of the flow-induced noise from a flag in a free stream

Abstract

An experimental study on the flow-induced noise from a flag was performed using a low-noise wind tunnel. In the experiment, simultaneous measurements of the noise from the flag and its displacement were performed and their relations were discussed. Experimental results showed that a highly periodic flow-induced noise that had strong directivity in the vertical direction was generated from the flag and its Strouhal number based on the streamwise length of the flag had a constant value. In addition, it was shown that the noise source of the periodic noise was the center of the trailing edge of the flag from the results of displacement measurements.