Dynamic stall produces a significant limitation
on the operation and performance of rotorcraft at
high-speed. To understand this complex and
unsteady aerodynamic phenomenon, a number of
studies have been performed to obtain and analyze
test data from nonrotating oscillating wings in wind
tunnels. Many of these experiments have failed to
generate sufficient information to capture the complicated
aerodynamic flow characteristics occurring
during the dynamic stall process. However, data from
one test are now available that afford an opportunity
for detailed analysis.
The Army Aeroflightdynamics Directorate
performed the test at Ames Research Center in a 7-
by 10-foot wind tunnel. The objective of the experiment
was to produce high quality data of two-dimensional
(2-D) and three-dimensional (3-D)
dynamic stall on a semi-span and full-span wing
undergoing pitching motions designed to simulate
typical rotor blade motions. The airfoil section, a
NACA 0015, was tested at a Mach number of 0.3.
Various tests were performed for a combination of
parameters such as pitch oscillation amplitudes and
reduced frequencies. Results from this experiment
included the integrated measurements from pressure
transducer arrays in the form of lift, drag, and pitching
moment coefficients at various wing span locations.
Instantaneous pressure distributions have now
been made available as a part of the present work;
examples are shown in figures 1 and 2.
The initial work here has focused on the 2-D data
of the Army experiment to study the vortex development
during the dynamic stall process under different
test conditions. Detailed analysis has been completed
to better understand the flow characteristics of the
NACA 0015 airfoil undergoing dynamic motion
during dynamic stall. Additionally, the flow behavior
data of the NACA 0015 airfoil in this experiment has
been compared with NACA 0012 airfoil data previously
obtained under similar operating conditions in
the same 7- by 10-foot wind tunnel.
Point of Contact: M. Rhee
(650) 604-3646
mrhee@mail.arc.nasa.gov
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