内壁周向振动的同心圆筒湍流减阻控制数值研究

It is known that periodic lateral wall oscillation can greatly reduce the friction drag in turbulent channel or pipe flows. In concentric annulus, the constant rotation of the inner cylinder can intensify turbulence fluctuations and enhance skin friction due to the centrifugal instability. In the present study, the effect of periodic oscillation of the inner wall on turbulent flows through concentric annulus is investigated by direct numerical simulations. The radius ratio of the annulus is 0.1, and the Reynolds number based on bulk mean velocity Um and the half annulus gap H is 2225. Different oscillation periods are considered, and drag reduction rates vary attributed to the different vortex structures near the inner wall. Investigation into the flow field shows that for short oscillating periods, the Stokes layer formed by the oscillating wall can effectively intervene the near-wall coherent motions of the turbulent flow and hence cause the turbulence suppression and skin friction reduction; but for longer periods, the centrifugal instability has enough time to develop and forms Taylor vortices, resulting in the enhancement of turbulence intensity and friction drag.