Effects of Coriolis force on coherent structure of wall turbulence

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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.