Structure of Turbulent Channel Flow under Spanwise System Rotation

抄録

Direct numerical simulation of turbulent channel flow under spanwise system rotation is performed. When system rotation is imposed on turbulent Poiseuille flow, the Reynolds number decreases in one side of a channel, while it increases in the other side. Hence, the effects of the Reynolds number as well as spanwise system rotation cannot be negligible in turbulent Poiseuille flow. To exclude the Reynolds-number effects, we performed the numerical simulation of open channel flow where the free-slip boundary condition is imposed on one wall, and the Reynolds number defined by the friction velocity and channel width can be always constant. When system rotation is imposed to enhance the spanwise vorticity of the mean shear, large-scale turbulence is attenuated and the mean velocity gradient increases over an entire channel. In contrast, when system rotation is imposed in the opposite sense to the mean spanwise vorticity, the mean velocity is leveled and small-scale turbulence is markedly decreased. We also investigate the effects of system rotation on the longitudinal vortical structure typically observed in near-wall turbulence.