The Eddy Viscosity Constitutive Relations And Control Of Reynold-stress For Coherent Structures In Wall Turbulence

Undisturbed flat-plate and flat-plate disturbed by periodic blowing and suction disturbance with 16,32,64Hz frequencies are studied and compared to perform the investigation of coherent eddy structures control and drag reduction principle in turbulent boundary layer in order to provide experimental base to refine the complex eddy viscosity modeling of multi-scale coherent eddy structures.Time sequence of streamwise direction velocity component and velocity gradient within and without 16,32,64Hz periodic blow-suction disturbance along different wall-normal direction positions have been finely measured by IFA300 constant temperature anemometer and parallel-two-hot-wire-sensor probe in a low-speed wind tunnel with resolution higher than Kolmogorov temporal scale. The distance between the two measured points is 1mm.The turbulent fluctuating velocity signals are decomposed into multiple-temporal-scale components by multi-scale wavelet analysis. The time scales of the multi-scale eddy structure are determined by self-correlation function of single-scale signals. The ejecting and sweeping progress of multi-scale coherent eddy structure in turbulent boundary layer is detected by wavelet coefficient.The multi-scale coherent structure component and non-coherent component of the velocity is separated with conditional sampling methods. Phased-average waveforms of velocity gradient of multi-scale coherent eddy structures and Reynolds-stress that the no-coherent components contribute to the coherent structure in turbulent boundary layer are extracted by phased-average method. The complex eddy viscosity modeling of multi-scale coherent eddy structures is investigated too.The phase relationship between Reynolds-stress component that the no-coherent contribution to the coherent structure and velocity gradient of multi-scale coherent eddy structures over undisturbed and disturbed flat-plate in bursting process is studied by cross-correlation function of phased-average waveforms .The influence of periodic blowing and suction disturbance on turbulent boundary is finely investigated.