Abstract
The behavior of organized motion in an open-channel flow over a concave bed is analyzed by using wavelet transforms. Experimental data of the velocity are obtained by a particle image velocimetry (PIV). Before detecting coherent structures, we employ a maltiresolutional analysis (MRA) for evaluating the accuracy of the PIV velocity data. The high frequency components of the velocity time-series suffer from noise data, so that we reconstruct the velocity time-series without the high frequency components. Then, the distributions of moduli of the velocity fluctuation vectors are analyzed using a two-dimensional continuous wavelet transform (2D-CWT) to extract the organized motion. The spatial scale and location of the organized motion are detected from the maximal values of the wavelet coefficients. The result suggests that the wavelet transform is a useful tool for analyzing the organized motion of this flow.
