Abstract
Approaching process of the turbulent pipe flow subjected by sudden change of the wall roughness has been investigated experimentally. The mean velocity, streamwise turbulent intensity, Reynolds stress profiles and the local wall shear stress were measured for the initial stage of the process after change wall condition from rough to smooth. The mean velocity profiles show acceleration before approaching to fully-developed smooth wall flow; overshoot behavior can be seen for the relaxation process. The local wall shear stress takes larger value for the acceleration of the near wall mean velocity profile and corresponds to larger Reynolds shear stress near the wall.
