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Title:Experimental investigation of nonequilibrium and separation scaling in double-wedge and double-cone geometries
Author(s):Knisely, Andrew M
Director of Research:Austin, Joanna
Doctoral Committee Chair(s):Dutton, J. Craig
Doctoral Committee Member(s):Panesi, Marco; Lee, Tonghun
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Compressible Flow
T5 Reflected Shock Tunnel
Expansion Tube
Shock Boundary Layer Interactions
Heat Flux
Abstract:Experiments were performed in the Hypervelocity Expansion Tube (HET) and the T5 hypervelocity shock tunnel to investigate geometric and gas composition effects on a double-wedge and double-cone geometry. The high-speed flow over the models results in a complex shock boundary-layer interaction which is known to be sensitive to thermal and chemical nonequilibrium. High-speed shadowgraph and surface heat flux measurements are obtained for both geometries. Surface heat flux measurements of the laminar boundary layer for the double-wedge show good agreement between both facilities with proper nondimensionalization. High-speed shadowgraph imaging is used to study the flowfield startup processes. The shock interactions and separation location exhibit no transient processes once the nozzle reservoir reaches a steady stagnation pressure level in T5. Two of the primary shock-shock interaction types are identified for the double-cone. Augmented heat flux is observed for the Edney Type V interactions with the highest peak heating observed with the nitrogen test gas. However, transient heat flux measurements during the nozzle startup indicate that the peak heat flux is not captured by the thermocouples for the air case due to the highly local nature of heating in this shock configuration. The boundary-layer separation scaling based on triple-deck theory for a double-wedge is applied to the double-cone geometry. The pressure correlation for the double-cone is found to be in agreement with historical results. No significant response of the separation length to the gas composition, apart from changes in the freestream condition, are observed for the current experiments. In purely laminar interactions no dependence of the scaled separation on Reynolds number is observed. Reattachment heat flux indicates transitional behavior of the separated boundary layer for the high Reynolds number conditions. A consistent decrease in scaled separation length is found for transitional interactions.
Issue Date:2016-10-12
Rights Information:Copyright 2016 Andrew Marshall Knisely
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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