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Highly separated axisymmetric step shock-wave/turbulent-boundary-layer interaction
Published online by Cambridge University Press: 06 September 2017
Abstract
The unsteadiness of a shock-wave/turbulent-boundary-layer interaction induced by an axisymmetric step (cylinder/$90^{\circ }$-disk) is investigated experimentally at Mach 3.9. A large-scale separation of the order of previously reported incoming turbulent superstructures is induced ahead of the step
${\sim}30\unicode[STIX]{x1D6FF}_{o}$ and followed by a downstream separation of
${\sim}10\unicode[STIX]{x1D6FF}_{o}$ behind it, where
$\unicode[STIX]{x1D6FF}_{o}$ is the incoming boundary-layer thickness. Narrowband high-frequency instabilities shift gradually to more moderate frequencies along the upstream separation region exhibiting a strong predominance of shear-induced disturbance levels – arising between the outer high-speed flow and the subsonic bubble. Through spectral/time-resolved analysis of this high Reynolds number and large-scale separation, results offer new insights into the shear layer’s inception and evolution (convection, growth and instability) and its influence on interaction unsteadiness.
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References
Chandola et al. supplementary movie 1
High-speed schlieren corresponding to figure 7b and played at a rate of: t/To=1 (top), t/To=10 (bottom left) and t/To=100 (bottom right) per second in the video, where To is the characteristic timescale of upstream bubble pulsations. For h/δo=5.9 step at Me=3.9 and Ree= 6.1x107m-1(fo= 391 Hz). White square indicates region of interest considered in movie 2.
Chandola et al. supplementary movie 2
Highly separated axisymmetric step STBLI (left) with schlieren-based correlation between upstream separation shock displacement xson the top φ=0o and bottom of the image φ=180o (top right) and variation of respective shock displacement ΔxU* with time, where ΔxU*=(xs−xs,av)/L (bottom right). Played consecutively at (a) t/To=1, (b) t/To=10 and (c) t/T
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