Abstract
The experimental investigation of supersonic flow over a hemisphere was conducted using Nanoparticle-based Planar Laser Scattering (NPLS) technique in a supersonic quiet wind tunnel at Ma=2.68. Ahead of the hemisphere, boundary layer separation with the formation of a three-dimensional separated flow was observed, which was resulted from the interaction between the three-dimensional bow shock wave and the boundary layer. The complex flow structures of supersonic flow over the hemisphere were visualized. Based on the time correlation of NPLS images, time-space evolutionary characteristics of supersonic flow over the hemisphere were studied, and the evolutionary characteristics of the spanwise and streamwise large scale vortex structures were obtained, which have the features of periodicity and similar geometry.
Highlights
The experimental investigation of supersonic flow over a hemisphere was conducted using Nanoparticle-based Planar Laser Scattering (NPLS) technique in a supersonic quiet wind tunnel at Ma=2.68
Based on the time correlation of NPLS images, time-space evolutionary characteristics of supersonic flow over the hemisphere were studied, and the evolutionary characteristics of the spanwise and streamwise large scale vortex structures were obtained, which have the features of periodicity and similar geometry
Nanoparticle-based planar laser scattering (NPLS) which is used to measure the supersonic flow was developed at the National University of Defence Technology (NUDT)
Summary
The experiments were conducted in a supersonic quiet wind tunnel (KD-2) at the National University of Defense Technology (NUDT), at Ma=2.68, the total pressure of inflow is 1 atm, and the total temperature is 300 K. The wind tunnel was mainly composed of transition section, stability section, nozzle, test section and vacuum tank. The transition section is used to collect air from the ambient atmosphere, and the air is dried and rectified in the stability section. Air-breathing supersonic quiet wind tunnel has lower total pressure and smaller Reynolds number in experiment section than the blow-down wind tunnel, which is helpful to achieve the laminarization of nozzle. The nozzle and test section were integrated, and the optical windows are designed in the walls of test section.
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