Abstract
Experimental studies have been made on turbulent structures of water and drag-reducing turbulent flow in a straight duct of rectangular cross-section (15mm×30mm). Velocity measurements were made using a high-resolution CCD camera with a telecentric lens for Particle Image Velocimetry. Time averaged statistics of the turbulent flow show a reduction in both the wall-normal velocity fluctuations and the Reynolds stress through out the channel. Maps of fluctuating velocity vectors show dramatic suppression of vortical motions in drag-reducing polymer solution flow, where the formation of groups of the fluctuating velocity vectors orienting to the streamwise direction was observed near the wall.
