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Length scale for the estimation of buzz frequency in the limit of high mechanical blockage in mixed-compression intakes

Devaraj, MKK and Jutur, P and Rao, SMV and Jagadeesh, G and Anavardham, GTK (2021) Length scale for the estimation of buzz frequency in the limit of high mechanical blockage in mixed-compression intakes. In: Journal of Fluid Mechanics, 916 .

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Official URL: https://doi.org/10.1017/jfm.2021.230


Oscillatory flow features are common in the unstart of hypersonic mixed-compression intakes and can be classified as low-amplitude or high-amplitude oscillatory unstarted flows. The low-amplitude oscillatory unstarted flow is driven by the shear layer from shock interactions ahead of the cowl, while the high-amplitude oscillatory unstarted flow is driven by the separation caused by shock-boundary-layer interaction on the ramp. While previous studies have observed these flow features and reported their associated frequency, there is no simple criterion available for predicting which mode will occur, and there is a lack of consensus on the appropriate frequency scaling parameter. We study a mixed-compression hypersonic intake in a hypersonic wind tunnel by varying the internal contraction ratio and the throttling ratio to observe various kinds of unstart regimes. Two significant conclusions emerge from considering the results for high-throttling-ratio conditions 0.55)]]> from the current as well as previous studies. Firstly, the actual shock-on-lip condition at the cowl corresponding to the unthrottled condition, as observed from schlieren images, demarcates the boundary between the two modes of oscillatory unstart flows upon throttling. Secondly, a suitable length scale, defined as the extent of the subsonic region in the unstarted flow (as observed from the experimental schlieren images), gives the appropriate frequency scaling parameter (where is the stagnation acoustic speed).

Item Type: Journal Article
Publication: Journal of Fluid Mechanics
Publisher: Cambridge University Press
Additional Information: The copyright for this article belongs to the Authors.
Keywords: Boundary layer flow; Boundary layers; Frequency estimation; Hypersonic inlets; Schlieren systems; Wind tunnels, Frequency-scaling; Hypersonic intake; Hypersonic wind tunnels; Internal contraction ratio; Mixed compressions; Oscillatory flows; Shock boundary-layer interactions; Shock interactions, Shear flow, boundary layer; estimation method; oscillating flow; shear flow; shock wave; wind tunnel
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 04 Jun 2023 05:01
Last Modified: 04 Jun 2023 05:01
URI: https://eprints.iisc.ac.in/id/eprint/81747

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