Experimental investigation of supersonic boundary-layer tripping with a spanwise pulsed spark discharge array

Abstract

In this paper, a pulsed spark discharge plasma actuator array is deployed to control laminar–turbulent transition in a Mach 3.0 flat-plate boundary layer, and the subtle flow structures are visualized by nanoparticle planar laser scattering (NPLS) technique. Results show that the onset location of turbulence can be brought upstream by plasma actuation, corresponding to forced boundary-layer transition. Hairpin vortex packets evolved from the thermal bulbs play a vital role in the breakdown of laminar flow. With the help of a machine learning tool, all the relevant structures induced by plasma actuation are extracted from NPLS images, and a conceptual model of the hairpin vortex generation is proposed, including three stages: production and lift-up of the high-vorticity region, formation of the $\varLambda$ vortex and evolution of the hairpin vortex.

Experimental study on surface arc plasma actuation-based hypersonic boundary layer transition flow control

“…Surface arc actuation can quickly heat the boundary layer [38,42]. According to verified results [43], the wall heating causes the boundary layer to be thick, and local heating makes the transition happen earlier.…”

“…The hairpin vortex structure induced by surface arc actuation plays a crucial role in the process of promoting boundary layer transition. The conceptual model of hairpin vortex generation and evolution was proposed, which preliminarily revealed the physical process of the boundary layer transition promoted by surface arc actuation, which can be divided into three stages: generation and lifting of high vorticity region, formation of Λ vortex and evolution of hairpin vortex [38]. In the case of hypersonic flow, we will reveal this process by means of high-precision flow field display technology in a subsequent investigation.…”