進行波制御下の乱流境界層流れに対するLDV計測と抵抗低減メカニズムの解析

We conducted a detailed analysis on the experimental data of the traveling wave control for zero pressure gradient turbulent boundary layer flow in which the drag reduction rate resulted in 7%. The free stream velocity is 2.0 m/s and Reynolds number based on the momentum thickness of the measurement section is 640 - 900 and the frictional Reynolds number is 300 - 340. It was confirmed that the traveling wave parameters; amplitude, wavelength, and wave speed are the same as that of the previous experiment conducted in the channel flow. We calculate laminar, turbulent Reynold shear stress (RSS), and periodic component in the same period with the control of FIK identity to analyze the contribution of local friction coefficient dividedly. As a result, the contribution of the turbulent component to the friction coefficient was decreased by the control while the periodic component was increased. Although the mean convection term was not directory calculated, the fact that the displacement thickness was thickened by the control suggests that this term was modified by the control to reduce skin friction. However, contributions of the RSS for the friction coefficient might be overestimated because some regions with the strong negative RSS which had been found in the previous DNS could not be measured.