Abstract
Asymptotic process of turbulent pipe flow has been investigated experimentally in relaxation process after sudden change in wall roughness from smooth to rough. k-type rough wall was placed at the position where the fully developed smooth pipe flow is established. Mean velocity and turbulent quantities were measured with hot-wire anemometer, and velocity and length scales were obtained from experimental data. Behavior of boundary layer thicknesses are considerably difference between for rough to smooth and smooth to rough. However, development of internal boundary layer thickness and streamwise distance to reach the asymptotic equilibrium situation are roughly the same for smooth to rough and rough to smooth.
