Abstract
Drag reduction phenomenon of a pulsating turbulent pipe flow has been experimentally examined when the cycle-averaged friction Reynolds number based on the friction velocity, the radius and the kinematic viscosity was set to be 110. The rotating speed of a vortex pump was periodically changed for generating the pulsating flow. The turbulence statistics were measured by Particle Image Velocimetry (PIV). The cycle-averaged Reynolds shear stress was deteriorated in the near-wall region at y^+<60, resulting in the efficient drag-reduction effect. The phase-averaged Reynolds shear stress aty^<60 was decreased in almost all the phases.
