Flow visualization of dynamic stall on an oscillating airfoil
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Authors
Brydges, Bruce E.
Subjects
Dynamic Stall
Dynamic lift
Unsteady lift
Helicopter retreating blade stall
Oscillating airfoil
Flow visualization
Schlieren method
Dynamic lift
Unsteady lift
Helicopter retreating blade stall
Oscillating airfoil
Flow visualization
Schlieren method
Advisors
Chandrasekhara, Muguru S.
Chandrasekhara, M.S.
Date of Issue
1989-09
Date
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
Stroboscopic schlieren photography was used to investigate the efFects of
compressibihty, reduced frequency, and amphtude on the dynamic stall of a
NACA 0012 airfoil subjected to sinusoidal oscillation. The Mach number was
varied from M^o = 0.25 to M^o = 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 am = 5° and am = 10
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.
Type
Thesis
Description
Series/Report No
Department
Aeronautical Engineering
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
Sponsors
Funder
Format
105 p.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.