Drag reduction effect by a wave-like wall-normal body force in a turbulent channel flow
Drag reduction effect by a wave-like wall-normal body force in a turbulent channel flow
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DOI：
10.1063/1.4901186
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发表时间：
2014-11
影响因子：
4.6
通讯作者：
H. Mamori;K. Fukagata
中科院分区：
文献类型：
--
作者：
H. Mamori;K. Fukagata
采用直接数值模拟的方法，研究了充分发展槽道湍流中波浪形壁面法向体力的减阻效应。流速保持恒定;体雷诺数设定为5600，这对应于非受控流中约180的摩擦雷诺数。假设壁面法向体积力呈指数衰减，使得体积力仅作用在壁面附近的区域。摩擦阻力被发现减少时，波在上游方向上的速度比体积平均速度慢的波传播;约40%的最大减阻率是在一个固定的控制输入的情况下实现的。净节能率，但是，被发现大多是负面的，如果积极的，微妙的。流场的可视化显示了流向涡结构的衰减和展向辊状涡的存在。展向滚柱涡在近壁区产生负雷诺切应力，有助于减小摩擦阻力。线性分析表明，展向辊状涡很好地描述了一个线性化的Navier-Stokes方程。
Skin-friction drag reduction effect of a wave-like wall-normal body force in a fully developed turbulent channel flow is investigated by means of direct numerical simulation. The flow rate is kept constant; the bulk Reynolds number is set at 5600, which corresponds to the friction Reynolds number of about 180 in the uncontrolled flow. An exponential decay of the wall-normal body force is assumed so that the body force acts in the regions near the walls only. The friction drag is found to decrease when the wave travels in the upstream direction at slower wavespeeds than the bulk-mean velocity; the maximum drag reduction rate of about 40% is achieved in the case of a stationary control input. The net energy saving rate, however, is found to be mostly negative and, if positive, subtle. Visualization of the flow field shows attenuation of streamwise vortical structures and existence of spanwise roller-like vortices. The spanwise roller-like vortices are found to produce a negative Reynolds shear stress in the regions near the walls, which contributes to the reduction of friction drag. A linear analysis reveals that the spanwise roller-like vortices are well described by a linearized Navier-Stokes equation.