壁面粗さが急変化した円管乱流の応答に関する研究

抄録

Transition process of turbulent pipe flow after sudden change in wall roughness has been investigated experimentally. The wall roughness is changed from k-type rough wall to hydrodynamically smooth wall. Over non-equilibrium stage after the sudden change of wall roughness, the mean velocity and the local wall shear stress were measured and discussed for transition process based on the wall law. The local wall shear stress was obtained with the aid of sublayer plate method.

The logarithmic layer in the mean velocity profile appears relatively early stage of the transition process. However, the profile is shifted downward just after the change of surface and then shifted upward in its downstream locations. The scaling law of the velocity gradient seems to have 1/0.41 at immediately after the sudden change of wall roughness, x/D=9.