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Published October 2013 | Published
Journal Article Open

Scaling of heat transfer augmentation due to mechanical distortions in hypervelocity boundary layers


We examine the response of hypervelocity boundary layers to global mechanical distortions due to concave surface curvature. Surface heat transfer and visual boundary layer thickness data are obtained for a suite of models with different concave surface geometries. Results are compared to predictions using existing approximate methods. Near the leading edge, good agreement is observed, but at larger pressure gradients, predictions diverge significantly from the experimental data. Up to a factor of five underprediction is reported in regions with greatest distortion. Curve fits to the experimental data are compared with surface equations. We demonstrate that reasonable estimates of the laminar heat flux augmentation may be obtained as a function of the local turning angle for all model geometries, even at the conditions of greatest distortion. This scaling may be explained by the application of Lees similarity. As a means of introducing additional local distortions, vortex generators are used to impose streamwise structures into the boundary layer. The response of the large scale vortices to an adverse pressure gradient is investigated. Surface streak evolution is visualized over the different surface geometries using fast response pressure sensitive paint. For a flat plate baseline case, heat transfer augmentation at similar levels to turbulent flow is measured. For the concave geometries, increases in heat transfer by factors up to 2.6 are measured over the laminar values. The scaling of heat transfer with turning angle that is identified for the laminar boundary layer response is found to be robust even in the presence of the imposed vortex structures.

Additional Information

© 2013 AIP Publishing LLC. Received 22 March 2013; accepted 2 October 2013; published online 30 October 2013. This work was funded through the Air Force Office of Scientific Research Young Investigator Award No. FA9550-08-1-0172 with Dr. John Schmisseur as program manager. The authors would like to thank Ryan Fontaine, Dr. Manu Sharma, Andrew Knisely, and Dr. Andy Swantek for their contributions to this work.

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