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Experimental study of the unstart/restart process of a two-dimensional supersonic inlet induced by backpressure
Author(s): Yi-long Zhao, Yong-yi Zhou, Yu-xin Zhao
Keywords: Supersonic inlet, Backpressure, Unstart, Shock configuration, Boundary layer separation, Wind tunnel, Flow visualization
Unstart/restart phenomena induced by backpressure in a general inlet with a freestream Mach number of 2.7 are investigated in an in-draft supersonic quiet wind tunnel. The boundary layer is turbulent developed on the forebody while it is laminar on the lip wall, which is closer to the real flying conditions. The high-speed Schlieren imaging system and the nanoparticle-based planar laser scattering (NPLS) method are used to visualize the inlet flowfield. The Particle Image Velocimetry (PIV) method is adopted. The inlet wall pressure is measured by high-frequency pressure transducers. The backpressure is reproduced by downstream transverse jets other than mechanical throttlers, which is more suitable to mimic backpressure caused by combustion. The high spatio-temporal resolution full-view images of inlet flow features during the complete unstart/restart process are captured, which are seldom seen before. The formation and disappearance process of massive boundary layer separation at the entrance of the unstarted inlet is observed. The backpressure transmits upstream through the shock wave/boundary layer interaction (SWBLI) regions. The shock structures change the angles and merge upstream to balance the pressure rise. The mach shock reflection configuration is observed in both unstart/restart process, accompanied by the boundary layer separation extending to the leading edge. The experiment also revealed notable hysteresis in the unstart/restart process.

Journal of Applied Fluid Mechanics

The Journal of Applied Fluid Mechanics (JAFM) is an international, peer-reviewed journal which covers a wide range of theoretical, numerical and experimental aspects in fluid mechanics. The emphasis is on the applications in different engineering fields rather than on pure mathematical or physical aspects in fluid mechanics. Although many high quality journals pertaining to different aspects of fluid mechanics presently exist, research in the field is rapidly escalating.