Effects of Coriolis force on coherent structure of wall turbulence

旋转通道的平均速度分布由三个参数控制；Re^*=u^*D/nu, OMEGAD/u^ <*2>和OMEGAD/u^*，其中u^*， D和OMEGA分别为摩擦速度，通道半高和角速度。本研究提出的流态空间可以很方便地理解科氏力和雷诺数的综合效应。墙律受科里奥利力效应的影响。这些效应表示为Van-Driest、Karmann和积分常数为OMEGAnu/u^<*2>的函数，而不是普遍常数。证明了科里奥利区域的存在，其中流动只受科里奥利力的影响，并发展了速度定律。压力侧的雷诺应力uv随着喷射作用的增加而增大。在吸力侧，情况正好相反。扫描和相互作用过程对我们的贡献在旋转通道中没有显示出太大的变化。然而，当吸力侧发生再层化时，横扫和喷射过程都减弱，uv<相似或等于>。u和v的相关系数在压力/吸力侧增大/减小，表明在旋转通道中湍流结构发生了变化。在吸力侧低波数范围内，v速度分量的功率谱明显减小。当旋转雷诺数（2D）^2OMEGA/nu =<正负>140时，在y+=80处测得的v谱分布中，波数=0.3处出现拐点。这种不连续性是由时间尺度为pi/OMEGA的湍流运动引起的；频道旋转的半时段。用VITA技术检测爆发不能很好地应用于这种流。

Mean velocity profiles in a rotating channel are governed by three parameters ; Re^*=u^*D/nu , OMEGAnu/u^<*2> and OMEGAD/u^* where u^*, D and OMEGA are friction velocity, channel half height and angular velocity respectively. A flow regime space suggested in this research is shown to be very convenient to understand the over all effects of Coriolis force and the Reynolds numbers. The wall law is affected by the Coriolis force effect. The effects are expressed as the Van-Driest, Karmann and integral constants being functions of OMEGAnu/u^<*2> instead of being universal constants. The Coriolis region where flows are affected only by the Coriolis force is shown to exist and the velocity law is developed.The Reynolds stress uv at a pressure side increases as a result of increase of contribution from ejection process. At a suction side, the situations are reversed. The contributions to us from sweep and interaction processes do not show much change in a rotating channel. However, when relaminarisation occur at suction side, both sweep and ejection processes weaken and uv<similar or equal>0. The correlation coefficient between u and v increases/decreases at pressure/suction side which shows the turbulent structure change to occur in a rotating channel. The power spectrum of v velocity component reduces appreciably in a low wave number range in a suction side. There appears a knee point at wave number=0.3 in a spectrum distribution of v measured at y+=80 when the rotation Reynolds number (2D)^2OMEGA/nu =<plus-minus>140. This discontinuity is caused by the turbulent motion having the time scle of pi/OMEGA ; half time period of channel rotation. The VITA technique to detect the burst can not well be applied to this flow.