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Published January 2010 | Published
Conference Paper Open

Hot-Wire Measurements of the Influence of Surface Steps on Transition in Favorable Pressure Gradient Boundary Layers


An examination of the effects of surface step excrescences on boundary layer transition was performed, using a unique experimental facility. The objective of the work was to characterize the variation of transition Reynolds numbers with measurable step size and boundary layer parameters, with the specific goal of specifying new tolerance criteria for laminar flow airfoils, alongside a fundamental investigation of boundary layer transition mechanisms. This paper focuses on interpretation of hot-wire measurements, including supporting stability calculations, undertaken as part of the study. The results for both forward and aft-facing steps indicated a substantial stabilizing effect of favorable pressure gradient on excrescence-induced boundary layer transition. These findings suggest that manufacturing tolerances for laminar flow aircraft could be loosened in areas where even mild favorable pressure gradients exist.

Additional Information

© 2010 Northrop Grumman. The authors acknowledge funding and support from the Air Force Research Laboratory, Prof. Mike Gaster of Queen Mary College, University of London, for the use of the Rapid-N code, and Prof. Bill Saric for useful advice.

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Published - AIAA-2010-374.pdf


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