Experimental Investigation Of Complex Eddy Viscosity Modeling Of Multi-scale Coherent Structure In Turbulent Boundary Layer

In this paper, the measurement technique of constant temperature anemometry is used in a wind tunnel to perform the study of the complex eddy viscosity modeling of multi-scale coherent structure in turbulent boundary layer.In the present experiment, time sequence of stream velocity components and normal gradient of stream velocity at different normal positions in a turbulent boundary layer above a smooth flat plate has been finely measured by IFA300 constant temperature anemometer and parallel-two-sensor hot-wire probe, with resolution higher than Kolmogorov scale. The distance between the two measured positions is 1mm in normal spatial direction. In the same way, time sequence of stream velocity component and normal velocity component at the positions mentioned above has been measured by X-two-sensor hot-wire probe.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 multi-scale coherent eddy structure in turbulent boundary layer is detected through taking multi-scale wavelet coefficient of stream velocity component signal as characteristic quantity. The multi-scale coherent structure component and non-coherent component of stream velocity is separated with conditional sampling methods. Conditional phased-average waveforms of normal gradient of the stream velocity of multi-scale coherent eddy structures and Reynolds-stress component that the no-coherent components contribute to the coherent structure in turbulent boundary layer are extracted by the conditional phased-average method.The phase relationship between Reynolds-stress component that the no-coherent contribution to the coherent structure and normal gradient of the stream velocity of multi-scale coherent eddy structures in bursting process is studied by cross-correlation function. The complex eddy viscosity modeling of multi-scale coherent eddy structure in turbulent boundary layer is discussed and the variation of the complex eddy viscosity along the normal position in turbulent boundary layer is investigated.