WITHDRAWN: Visualization of Görtler vortices in high–enthalpy plasma flow using planar laser-induced fluorescence

Abstract

The Görtler vortices phenomenon is a characteristic flow feature observed in the boundary layer of the compressed ramps in hypersonic flow. In the context of high-enthalpy plasma flow during aerospace re-entry processes, there is currently a lack of effective means to visualize Görtler vortices of the boundary layer. In this study, the nitric oxide planar laser-induced fluorescence (NO PLIF) technique was employed to visualize the boundary layer of a ramp in a 50 MW arc-heated wind tunnel. The Görtler-like vortex structures were observed in the boundary layer of the ramp. This is the first time that Görtler vortices have been clearly observed in high-enthalpy plasma flow. Through varying the flow conditions, it was found that Görtler vortices persisted in the boundary layer of the ramp when the total enthalpy of the arc-heated wind tunnel exceeded 12.3 MJ/kg. And the position of the Görtler streaks was found to be non-fixed, while the average Görtler wavelength remained approximately 30 mm at 10° ramp and showed limited variation with the total enthalpy. Additionally, a sheet forming optics system with adjustable angle and height was designed to enable visualization of Görtler vortices in the boundary layer of the ramp at different angles and heights. The vortex structures on low-angle ramp exhibit better stability and shorter wavelength. Meanwhile, the visualization results at different heights have confirmed that the wavelength of the Görtler vortices is approximately equal to the boundary layer thickness. This work demonstrates the feasibility and potential of the PLIF technique in visualization of the boundary layer in plasma flow, especially in regard to the Görtler vortices.