Abstract
Experimental investigation for a periodically converging-diverging turbulent pipe flow is performed to examine drag reduction effect with LDV (Laser Doppler Velocimetry) and differential pressure experiment. A shape of the pipe is designed according to a result of a direct numerical simulation. Three periods of the converging-diverging are provided. At the bulk Reynolds number of 4000, maximum drag reduction rate is obtained: the drag reduction rates are 8%, 12% and 14 at the first, second and third period, respectively. Therefore, the drag reduction rate is found to develop in the downstream direction. According to LDV, the mean streamwise velocity and the RMS value of streamwise velocity show a similar tendency with the result obtained by the direct numerical simulation.
