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

Authors: Glen T. Duncan Jr.; Brian K. Crawford; Matthew W. Tufts; William S. Saric; Helen L. Reed

Addresses: Department of Aerospace Engineering, Texas A&M University, College Station, TX, 77843-3141, USA ' Department of Aerospace Engineering, Texas A&M University, College Station, TX, 77843-3141, USA ' Department of Aerospace Engineering, Texas A&M University, College Station, TX, 77843-3141, USA ' Department of Aerospace Engineering, Texas A&M University, College Station, TX, 77843-3141, USA ' Department of Aerospace Engineering, Texas A&M University, College Station, TX, 77843-3141, USA

Abstract: 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; pressure measurement.

DOI: 10.1504/IJESMS.2014.063127

International Journal of Engineering Systems Modelling and Simulation, 2014 Vol.6 No.3/4, pp.171 - 180

Published online: 26 Jul 2014 *

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