Accession Number:

ADA058714

Title:

Unsteady Boundary Layer Flow Reversal in a Longitudinally Oscillating Flow.

Descriptive Note:

Final rept. Aug 75-Aug 78,

Corporate Author:

FRANK J SEILER RESEARCH LAB UNITED STATES AIR FORCE ACADEMY COLO

Personal Author(s):

Report Date:

1978-08-01

Pagination or Media Count:

140.0

Abstract:

Measurements of boundary layer flow reversal made in a wind tunnel on a stationary NACA 0012 airfoil immersed in a longitudinally oscillating subsonic flow are described. A split-film sensor provided flow reversal data in regions above the airfoil surface throughout the period of flow oscillation. At angles of attack below the steady-flow stall angle of attack and for small amplitude oscillations, regions of boundary layer flow reversal near the leading edge were observed to vay nominally in phase with e time-varying external velocity. However, an increase in the oscillation amplitude produced a phase lead and an increased downstream extent of the flow reversal region. It is shown that boundary layer flow reversal on a stationary airfoil in an oscillating free stream responds to changes in the flow unsteadiness in a manner similar to the flow reversal observed during the onset of dynamic stall on an airfoil oscillating in pitch.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE