Phase Delay Of The Reynolds Stress And Wall Pressure Fluctuations To The Strain Rate Of The Large Scale Structures In Wall Shear Flows

The turbulent boundary layer is a very complex system, now it has been accepted that coherent structures are important structures in shear turbulence, and the research on them have great sense in foundation research and engineering. Different from traditional Reynolds stress , the Reynolds stress caused by small vortex changed as time changed in the coherent structures'scale. Our works mainly investigated the relations between the Reynolds stress caused by small vortex and strain rate of large vortex in the coherent structures'scale. Then the relations between the wall pressure fluctuations and the strain rate of large vortex was considered too.The experiments were carried on in the wind tunnel, periodic disturbance of wake flow of a circle cylinder was introduced into the outer layer of turbulent boundary layer of plate .High accuracy pressure transducer and hot wire/film anemometer were used to measure the velocity and wall pressure fluctuations synchronously. Phase averaging, wavelet analysis and power spectrum analysis had been used to do data processing.At first, we analyzed the characters of the flow field affected by the wake flow of near wall cylinder. In the thick turbulent boundary layer,we investigated the effects of the gap ratio on the wake shedding of the near wall circular cylinder and the wall pressure fluctuations. We gained the regularity of the Strouhal number of shedding vortex varying as the gap ratio and Reynolds number, the results had a little difference with the former people. We also gained the regularity of the periodic components of the wall pressure fluctuations. The disturbend range of the wake of the air turbulent boundary layer in a certain Reynolds number had also been gained.Based on the above results, we choose a proper location for the circular cylinder to investigate the phase delay of the Reynolds stress and the wall pressure fluctuations in the coherent structures'scale to the strain rate of large scale structures. The experiments results confirmed the rationality of the plural form of the eddy viscosity coefficient in the turbulence model, we also gained the varied characters of the phase delay along the time and space between those variables. Our work provided some experimental and theoretical proofs to construct more practical turbulent model in future. It also deepened our knowledge in turbulence and flow around the circular cylinder near wall. All those results made a good foundation for further study.