0620 壁面一様吹出し/吸込みの空間発達乱流境界層への影響

Abstract

A series of large-eddy simulations of the spatially developing turbulent boundary layer with uniform blowing or suction at moderate Reynolds number, based on the free-stream velocity and the momentum thickness, up to Re_θ = 2500 are performed. Similarly to the previous work of the direct numerical simulation at low Reynolds number [Kametani & Fukagata, J. Fluid Mech., vol. 681, pp. 154-172, 2011], uniform blowing achieves the skin friction drag reduction and enhancement of the turbulence, while uniform suction has the opposite trends. In spite of blowing at 0.1% of free-stream velocity, around 18% of drag reduction is achieved. The root-mean-squares of turbulent uctuations and the spectral analysis show that blowing/suction affect the turbulence at the outer region notably. The distributions of the power-spectral density of streamwise velocity uctuation and the cross-spectra of the Reynolds shear stress are strongly distorted in the outer region. The decomposition of the skin friction drag indicates that blowing has potential to reduce skin friction drag despite it increases the turbulence even at moderate Reynolds numbers.