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Title: Transonic shock/boundary layer interactions subject to downstream pressure perturbations
Author: Bruce, P. J. K.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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In the present study, an experimental investigation into the response of transonic SBLIs to periodic downstream pressure perturbations in a parallel walled duct has been conducted. Tests have been carried out for shock strengths of M = 1.4 and 1.5 with pressure perturbation frequencies in the range 16-90 Hz. Analysis of the steady interaction at M = 1.3, 1.4 and 1.5 has also been made. For all unsteady test cases, the transonic shock was observed to undergo periodic oscillatory motion in the streamwise direction. This motion changes the relative shock strength, which causes the inter-action structure to vary during oscillations. The dynamics of shock motion are determined primarily by the imposed pressure ratio. At high frequency, viscous effects were observed to have an effect on the interaction structure and shock dynamics. Inviscid analytical and computational models for the prediction of shock dynamics in ducts have been developed. Based on these, a non-dimensional model for the relationship between the amplitude and frequency of shock motion in a diverging duct has been proposed. At low frequencies, shock oscillation amplitude is constant and dominated by duct geometry. At moderate frequencies, amplitude is inversely proportional to frequency and duct geometry is unimportant. At high frequencies, the amplitude of oscillations are small and viscous effects become significant. These viscous effects are most significant during rapid changes in relative shock strength. Shock acceleration, which increases with frequency, is the key variable which determines their importance. It is postulated that the finite time taken for changes in the viscous SBLI structure to occur is at the origin of the observed behaviour. The relevance of the study to real-world applications where unsteady SBLIs occur is discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available