Wavelet analysis of the wall pressure fluctuation in drag reducing pipe flow has been made for various dilute polymer solutions and aqueous detergent solutions in order to discuss the correlation between drag reduction and pressure fluctuation. In the diagram of the root mean square of pressure fluctuation vs Reynolds number under the transition conditions, the peak is observed at a higher Reynolds number for drag reducing fluids than for water, and the magnitude of pressure fluctuation is also larger for the former fluid in averge than the latter. Wavelet analysis shows that pressure fluctuation is characterized by the peaks with high amplitudes appearing intermittently in time and that those high peaks tend to concentrate on a specific frequency range in the flow of drag reducing fluids.
