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Flight experiments on the effects of step excrescences on swept-wing transition

Published Online:pp 171-180https://doi.org/10.1504/IJESMS.2014.063127

A 30° swept-wing model with a movable, leading-edge extending to 15% chord is used in flight tests to study the effect of two-dimensional, step excrescences on swept-wing transition, where stationary-crossflow waves are typically the dominant instability. Transport unit Reynolds numbers are achieved using a Cessna O-2A Skymaster. Forward- and aft-facing steps are modulated in-flight. Pressure measurements are compared with CFD. Infrared thermography is used to globally detect boundary-layer transition. When the 2-D pressure gradient matches the unswept case, the swept-wing case has a lower Rekk,crit. However, there is still potential to relax conventional, laminar-flow tolerances for steps.

Keywords

2-D roughness, step excrescences, forward-facing step, backward-facing step, boundary-layer transition, laminar flow, transport Reynolds number, flight research, crossflow instability, swept wings

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