Accession Number : ADA222202


Title :   Flow Visualization of Dynamic Stall on an Oscillating Airfoil


Descriptive Note : Master's thesis,


Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA


Personal Author(s) : Brydges, Bruce E


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a222202.pdf


Report Date : Sep 1989


Pagination or Media Count : 116


Abstract : Stroboscopic schlieren photography was used to investigate the effects of compressibility, reduced frequency, and amplitude on the dynamic stall of a NACA 0012 airfoil subjected to sinusoidal oscillation. The Mach number was varied from M at infinity = 0.25 to M at infinity = 0.45 (corresponding to a Reynolds number variation of Re = 450,000 to Re = 810,000); the reduced frequency was varied from k = 0.025 to k = 0.10. Oscillation amplitudes of alpha sub m = 5 deg and alpha sub m = 10 deg were compared. Schlieren photographs are presented, which document the dynamic stall vortex formation, convection, and shedding sequence for various experimental conditions. Additionally, a preliminary examination of the flow reattachment process was conducted. Data derived from the photographs indicates that increasing the compressibility causes dynamic stall to occur at lower angles of attack; while, increasing the reduced frequency and/or the oscillation amplitude effectively delays dynamic stall effects to a higher angle of attack. Flow reattachment is sensitive to both Mach number and reduced frequency for low values of these parameters; when either the Mach number or reduced frequency is sufficiently high, the reattachment process stabilizes. (jhd)


Descriptors :   *FLOW VISUALIZATION , *SCHLIEREN PHOTOGRAPHY , *STALLING , *VORTEX SHEDDING , ANGLE OF ATTACK , AIRFOILS , VARIATIONS , HELICOPTERS , MACH NUMBER , LIFT , AMPLITUDE , OSCILLATION , REYNOLDS NUMBER , ROTOR BLADES , VORTICES , CONVECTION , STROBOSCOPES , DYNAMICS , THESES


Subject Categories : Aerodynamics


Distribution Statement : APPROVED FOR PUBLIC RELEASE