進行波状弾性壁面を有する円管内乱流の抵抗低減効果

抄録

Drag reduction effect of traveling wave control in turbulent pipe flow is experimentally investigated. A pipe is made of a rubber sheet in order to obtain a large wall deformation amplitude and it is set vertically. Three piezoelectric actuators are mounted at the upstream region of the test section as the vibration sources to produce downstream waves. Wave parameters show effective values for drag reduction by adjusting input parameters of the actuators. The drag reduction rate of 5% is obtained at the bulk Reynolds number of 4800. Laser Doppler velocimetry measurement is performed in order to evaluate the control effect on the flow field. The profiles of mean streamwise velocity and root mean square (rms) value of the streamwise velocity fluctuations in the uncontrolled case are in good agreement with those of DNS. When the traveling wave control is applied, the mean streamwise velocity gradient becomes smaller near the wall, which indicates the drag reduction effect. Rms values of the streamwise velocity in the controlled case is larger than those of the uncontrolled case. By conducting three-component decomposition, it is observed that a periodic component is generated near the wall, whereas a random component decreases compared with the uncontrolled case. Thus, the influence of the traveling wave control on the turbulent flow field near the wall in a pipe is experimentally confirmed.