TY - GEN
T1 - Oscillatory plunging motion applied to an airfoil near stall
AU - Agate, Mark A.
AU - Little, Jesse
AU - Fasel, Hermann
AU - Gross, Andreas
N1 - Funding Information:
This work has been supported by the U.S. Air Force Office of Scientific Research (FA9550-14-1-0184) with Dr. Douglas Smith serving as program manager. Additional support was provided through a National Defense Science and Engineering Graduate Fellowship and an Arizona-NASA Space Grant Consortium scholarship. Stephen Pineda and Ray Pitts assistance with the experiments is highly appreciated. Also appreciated is the support of the machine shop staff at UA (Dale Drew, Lane Hammond, and Joe Hartley)
Publisher Copyright:
© 2017 by Mark Agate; Jesse Little; Andreas Gross; Hermann Fasel.
PY - 2017
Y1 - 2017
N2 - The effects of high frequency (k = 0.70), low amplitude (h = 3.2% and 4.8%) oscillatory plunging motion on the X-56A airfoil are examined at Re = 2.0 × 105using wind tunnel experiments and implicit large eddy simulations. The objective of this work is to understand the fundamental physics associated with laminar separation bubbles in an unsteady environment that is representative of the motion experienced by high aspect ratio wings. For a nominal angle of attack of 10◦ and a wing motion with k = 0.70 and h = 3.2%, the static CLmaxis exceeded by about 20% thus delaying lift stall (static stall occurs at 12.25°). The moment coefficient oscillates around the static values with only minor deviations. Experiments, simulations, and unsteady inviscid theory (Theodorsen) show only minor differences in this case. For a nominal angle of attack of 12° for a wing motion with k = 0.70 and h = 4.8%, the results begin to deviate largely from the inviscid theory. CLmaxis exceeded by about 32% and lift stall occurs at angles of attack far beyond static stall. However, a strong moment stall occurs due to a “bursting” of the laminar separation bubble just before the bottom of the oscillation cycle as the maximum acceleration is approached. These results are confirmed experimentally through surface pressure and particle image velocimetry data. The lift coefficient obtained from the simulation differs from the experimental lift coefficient due to subtle variations in the bubble shedding dynamics, but the qualitative behavior is very similar. Efforts to assess the influence of grid resolution on the observed discrepancies between the experiment and simulation are ongoing.
AB - The effects of high frequency (k = 0.70), low amplitude (h = 3.2% and 4.8%) oscillatory plunging motion on the X-56A airfoil are examined at Re = 2.0 × 105using wind tunnel experiments and implicit large eddy simulations. The objective of this work is to understand the fundamental physics associated with laminar separation bubbles in an unsteady environment that is representative of the motion experienced by high aspect ratio wings. For a nominal angle of attack of 10◦ and a wing motion with k = 0.70 and h = 3.2%, the static CLmaxis exceeded by about 20% thus delaying lift stall (static stall occurs at 12.25°). The moment coefficient oscillates around the static values with only minor deviations. Experiments, simulations, and unsteady inviscid theory (Theodorsen) show only minor differences in this case. For a nominal angle of attack of 12° for a wing motion with k = 0.70 and h = 4.8%, the results begin to deviate largely from the inviscid theory. CLmaxis exceeded by about 32% and lift stall occurs at angles of attack far beyond static stall. However, a strong moment stall occurs due to a “bursting” of the laminar separation bubble just before the bottom of the oscillation cycle as the maximum acceleration is approached. These results are confirmed experimentally through surface pressure and particle image velocimetry data. The lift coefficient obtained from the simulation differs from the experimental lift coefficient due to subtle variations in the bubble shedding dynamics, but the qualitative behavior is very similar. Efforts to assess the influence of grid resolution on the observed discrepancies between the experiment and simulation are ongoing.
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U2 - 10.2514/6.2017-0998
DO - 10.2514/6.2017-0998
M3 - Conference contribution
AN - SCOPUS:85017218745
T3 - AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting
BT - AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting
PB - American Institute of Aeronautics and Astronautics Inc.
T2 - 55th AIAA Aerospace Sciences Meeting
Y2 - 9 January 2017 through 13 January 2017
ER -