The Investigation Into The Shock Wave/Boundary-layer Interaction Flow Field Organization

The present work studied the flow organizations of the shock wave/boundary layer interaction field in the supersonic/hypersonic air-breathing aircraft inner flow both from the experimental the numerical investigations.The method of direct numerical simulation(DNS) and lager-eddy simulation is developted, while the entropy splitting approach is adopted and the TVD shock capturing scheme and the artificial compression method(ACM) coupled with the Ducros sensor are implemented; The unsteady inflow turbulence generation methods of Digital-Filter and Recycling-Rescaling are realized; The Mixing time-scale sub-grid-stress model and one equation model are used in the LES simulation.Based on the flow visualizations with NPLS technique and DNS simulations, the coherent structures of the turbulent boundary layer are investigated. The conditional vortex structure companying the velocity streaks is observed, while the variation of the typical spanwise spacing of these structures are observed. The Lagrangian coherent structure(LCS) inner the turbulent boundary layer is detected with the FTLE method, based on which the convection effects inner the turbulent boundary layer is investigated, and the regeneration of the turbulence is discussed.The difference between the invisid shock reflection and the SWBLI field is analysed. The wave patterns, boundary layer distortions and separation scales in the SWBLIs with different shock strength are investigated, which suggests that the free-interaction theory does works for the SWBLI, from the start point of the interaction to the incident point of the shockwave on the distorted boundary layer. It is confirmed from the momentum balance that the pressure raise and the local velocity is the main part for balance of the SWBLI field. The low frequency unsteadiness of the SWBLI field is captured by the long-period LES simulation, which suggests that the dependence of the dynamic behaviour of the SWBLI on the interaction strengthen and independence of the time-averaged flow field both work.The large-scale convection structures inner the separated SWBLI field are revealed both by the NPLS visualization and PIV measurements and the massive DNS simulations, while their interactions with the reflected shock and incident shock are observed. It is confirmed from the spatial and temporal analyzing that the large-scale convection structures do have direct connection with the large-scale velocity structures in the outer part of the incoming boundary layer. The Lagrangian coherent structures in the SWBLI field is detected by the FTLE method, while the variation of the turbulent structure is observed inner the shear layer of the SWBLI field, starting from the separation point.The finit-spanwise effect induced by the sidewalls are investigated by the LES simulations, and the influence of the spanwise scale and sidewall boundary layer condition on the complex 3D main separation patterns are revealled. It is proved that the creation of the main shock distortion and secondary shock induced by the slept-back SWBLI on the sidewall, as well as their reflection in the corner regiona, are the main reason for the creation of 3D separation, and a physical model based on the developement of the main shock distortion is established.By the importing of the micro-ramp, the coherent structure of the incoming boundary layer is modified, while the flow organization control of the SWBLI is realized. It is found that the micro-ramp has a distinctive function of fluid collection and re-distribution inner the turbulent boundary-layer, which is the direct-reason for the low-speed and low-density feature of the wake. Compared to the velocity streakes of the incoming turbulent boundary layer, the spanwise location of velocity streaks imported by the micro-ramp is found to be more stable, which split the original large-scale separation into small bulks.