Study on Hysteresis Phenomenon and Local Non-equilibrium Turbulence in Couette-type Turbulent Flow

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1. Firstly, turbulence structure in plane turbulent Couette flow has been studied. The results obtained are as follows. (1) Turbulence structure in the wall region is similar to that in the two-dimensional channel flow. In the core region, however, turbulence structure is very different from the latter case because of the uniform shear existing there. (2) As turbulence energy is produced only on the streamwise turbulence quantity, the anisotropy of turbulence is greater than that of the channel flow. (3) Distributions of velocity fluctuating components show Gaussian and tripple velocity correlation is almost zero. Viscous diffusion and dissipation of turbulence energy balance throughout the core region. Energy transport u, v and w is due to the pressure-strain. (4) Sinuisoidal change of mean velocity distribution has been measured in the spanwise derection, so that large-scale motions having spanwise scale of eddies are conjectured to exist.2. Secondly, Couette-Poiseuille type turbulen … More t flow has been studied to investigate the hysteresis phenomenon in the core region and the local non-equilibrium turbulence which have been measured on the turbulent Couette-type flow with an alternative pressure gradient, having both stationary wavy and moving flat walls. The distribution of velocity in the Couette-Poiseuille type flow has been considered indepedently under the parameters of Reynolds number Re^<**>=hu_<**>/nu and d tau /dy. The results obtained are as follows. (1) Low of the wall is given by U^+=f(y^+, mu^<-1>), where y^+=u_<**>/nu and mu^<-1>=(nu d tau/dy)/(rhou_<**>^3). We clarified the effects of Re^<**> on Van Driest damping factor A^+ and additive constant B of the log-law for preferable (mu^<-1><0) and adverse (mu^<-1>>0) pressure gradient cases, respectively. (2) For positive value of d tau/dy, effects of betaXIrhou_<**>^2h/(d tau/dy) and Re^<**> on the half-power law is clarified. (3) Profiles of velocity defect law in the turbulent core region are only related to whether the flow is Couette-type (beta>-0.5) or poiseuille-type (beta<-0.5). Less