Supersonic Cavity Flows and Their Control

Abstract

A detailed experimental study of supersonic, Mach 2, flow over a three-dimensional cavity was conducted using shadowgraph visualization, unsteady surface pressure measurements, and particle image velocimetry. Large-scale structures in the cavity shear layer and visible disturbances inside the cavity were clearly observed. A large recirculation zone and high-speed reverse flow was revealed in the cavity. In addition, supersonic microjets were used at the leading edge to suppress flow unsteadiness within the cavity. With a minimal mass flux (blowing coefficient B c 0:0015), the activation of microjets led to reductions of up to 20 dB in the amplitudes of cavity tones and of more than 9 dB in the overall sound pressure levels. The microjet injection also modified the cavity mixing layer and resulted in a significant reduction in the flow unsteadiness inside the cavity as revealed by the shadowgraphs and the velocity-field measurements.

Visualization of wave propagation within a supersonic two-dimensional cavity by digital streak schlieren

“…It is known from previous studies that the convective velocity ratio has a dependency on the boundary layer thickness-to-cavity depth ratio (δ/D) for two-dimensional and axisymmetric cavities (Zhang and Edwards 1990;Zhang 1995;Zhuang et al 2006). This dependency was also noted by Bauer and Dix (1991) and has been confirmed by simulations and experiments in this study (see Sridhar 2014 and the values for k c given above).…”

“…In cavity flows, however, this approach may be susceptible to inaccuracies as pressure waves move back and forth and may interact with each other, so the matching would not necessarily correspond to the pressure wave created by the wave traveling with the structure in the shear layer. In other previous studies, the convective velocity was determined by particle image velocimetry (PIV) (Zhuang et al 2006) and via an image cross-correlation technique of PLIF images (Murray and Elliot 2001). Image cross-correlation techniques were developed mainly to track the movement of solid bodies, for which the technique has been shown to be quite useful.…”

Development and Implementation of High Bandwidth Pulsed Microactuators for Sub and Supersonic Applications

“…A similar control approach, based on steady microjet injection, was very effective in controlling the resonating flowfield associated with a supersonic cavity as well. By injecting steady microjets at the leading edge of a Mach 2 cavity, Zhuang et al [26] demonstrated a reduction of more than 8 dB OASPL inside the cavity and a 20 dB reduction in the cavity tones. The control effectiveness of steady microjets on these two problems is shown in Figure 1.…”

“…This actuation technique reportedly worked well for high angles of attack and is referred to as pulsed vortex generators. Bryant et al [24], Wiltse et al [25] and Smith et al [26] used piezoelectric actuators for imparting unsteady momentum for flow separation control. These actuators, also called synthetic jets, produce zero net mass flux jets with velocities in the range of 10-80 m/sec at a frequency range up to 1 kHz.…”

Transverse jet-cavity interactions with the influence of an impinging shock

“…17 Gruber et al 18 looked at how changes in the aft wall of an open cavity can lead to changes in the shear layer and hence the drag and residence time within the cavity. Sakamoto et al 19 revealed the complex three-dimensional nature of two-dimensional cavity flows, and the oscillatory nature of the leading edge cavity shock.…”