Experimental studies on flow visualization and velocity field of compression ramp with different incoming boundary layers

Abstract

Experimental studies which focus on flow visualization and the velocity field of a supersonic laminar/turbulent flow over a compression ramp were carried out in a Mach 3.0 wind tunnel. Fine flow structures and velocity field structures were obtained via NPLS (nanoparticle-tracer planar laser scattering) and PIV (particle image velocimetry) techniques, timeaveraged flow structures were researched, and spatiotemporal evolutions of transient flow structures were analyzed. The flow visualization results indicated that when the ramp angles were 25 • , a typical separation occurred in the laminar flow, some typical flow structures such as shock induced by the boundary layer, separation shock, reversed flow and reattachment shock were visible clearly. While a certain extent separation occurred in turbulent flow, the separation region was much smaller. When the ramp angles were 28 • , laminar flow separated further, and the separation region expanded evidently, flow structures in the separation region were complex. While a typical separation occurred in turbulent flow, reversed flow structures were significant, flow structures in the separation region were relatively simple. The experimental results of velocity field were corresponding to flow visualization, and the velocity field structures of both compression ramp flows agreed with the flow structures well. There were three layered structures in the U component velocity, and the V component velocity appeared like an oblique "v". Some differences between these two compression ramp flows can be observed in the velocity profiles of the shear layer and the shearing intensity.

Flow control of micro-ramps on supersonic forward-facing step flow

“…[16] It has been used to investigate the supersonic mixing layer, boundary layer, compression ramp, aerooptics, and so forth. [17][18][19] As shown in Fig. 4, the NPLS system is composed of a nano-particle generator, a dual-cavity Nd:YAG laser, an interline transfer double-exposure CCD camera, a synchronizer, and a computer.…”

Wall modeled large eddy simulation of supersonic flow physics over compression–expansion ramp

“…A pulsed-plasma jet actuator [12] was used to control the unsteadiness of separation shock in a Mach 3 compression ramp; HSPIV (high-speed particle image velocimetry) [13] was applied to research the low-frequency dynamics characteristics of the separation region. Wu et al [14,15] experimentally investigated a supersonic flow over several compression ramps in a Mach 3.0 wind tunnel. Results indicate that when ramp angles are 25°, a typical separation occurs in laminar flow, and a certain extent separation occurs in transitional flow, while separation does not occur in turbulent flows.…”