Flight experiments on laminar flow control in swept-wing boundary layers (An unlikely journey of a mechanician)
William Saric (Midwest Mechanics Seminar, Fluids)
2:30 PM on 2008-03-14
Flight experiments on laminar flow control in swept-wing boundary layers (An unlikely journey of a mechanician) William S. Saric Aerospace Engineering Texas A&M University College Station, Texas Data are presented on boundary-layer transition to turbulence in low-disturbance flight environments. The measurements include infra-red thermography and hotfilm anemometry to study roughness-related issues of boundary-layer transition on a swept-wing model that is mounted on the wing of a Cessna O-2 aircraft. A Navier-Stokes code is used calculate the aircraft flowfield and boundary layer while Nonlinear Parabolized Stability Equations (NPSE) quantify the stability measurements and transition locations. The laminarization scheme of spanwise-periodic distributed roughness elements (DRE) is investigated at chord Reynolds numbers of 8 million. Measurements were made to determine the transition locations for clean configurations and for enhanced surface roughness that simulates an operational surface finish. For clean configurations, natural laminar flow was achieved over 80% of the surface of a 37° swept-wing model at chord Reynolds numbers of 8.1 million. With a background surface roughness of 1 m rms, transition moved forward to 30% chord. The DRE delayed transition to 60% chord. The work was supported by: AFOSR, AFRL, and Northrop-Grumman Corporation.