Generation and propagation of pressure waves in supersonic deep-cavity flows

Frequencies of Transverse and Longitudinal Oscillations in Supersonic Cavity Flows

“…The upstream and downstream propagating waves were clearly visualized in a time-sequence of the schlieren flow images for / = 0.70 [8]. By carefully tracking these waves in the images, we obtain = 266 m/s and = 379 m/s.…”

“…We tried to visualize the pressure waves traveling inside the cavity of / = 1.8 using the schlieren technique with a spark light source whose duration time was ∼30 ns. However, no pressure waves appeared inside the cavity in the instantaneous schlieren images although the waves were clearly visualized for a deep cavity of / = 0.70 [8]. Chandra and Chakravarthy [15] also captured instantaneous schlieren images of Mach 1.5 flows over a rectangular cavity of / = 1.5 (which is close to / = 1.8).…”

“…The pressure-wave propagation inside a deep cavity was visualized in a time sequence of the schlieren images captured by Handa et al [8].…”

“…Using such models, the predominant oscillation frequencies can be estimated rather accurately for shallow cavities, but the estimation fails for deeper cavities because the effect of the cavity depth is not included in these models. Based on a flow visualization, Handa et al [7] recently developed a model accounting for the feedback mechanism of a transverse oscillation [8]. Their model estimates the dominant frequencies well for deep cavities whose lengthto-depth ratios are lower than 1.0.…”

“…Nitrogen gas flows into the test duct through a nozzle at a Mach number of 1.68. Detailed descriptions of the flow issuing from the nozzle are provided elsewhere [7,8]; on the basis of the boundary layer thickness, the flow issuing from the nozzle results in a boundary layer thickness of 0.73 mm and a Reynolds number of 1.03 × 10 4 . The test duct has a rectangular cross section with a height and width of 10.5 and 28.0 mm, respectively.…”