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Experimental Investigation of Dynamic Stall

05-19-2015 Dr. Nathan Webb, David Castañeda

Prof. Mo Samimy

Collaborative Center for Aeronautical Sciences Annual Review 2015

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About Me

• Graduated from Ohio State with Ph.D. in 2013 • Currently Post-Doctoral Researcher at the

Aerospace Research Center •  Interests

– Flow Control – Scramjet propulsion – Particle Image Velocimetry

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Introduction

• Dynamic Stall – The Good - Transient Lift Increase – The Bad - Transient Aerodynamic Forces

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After [1] (Visbal, 2014)

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Introduction

• Dynamic stall occurs in many applications – Rotorcraft/Maneuvering fixed-wing craft – Wind Turbines – Micro Aerial Vehicles

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[2] Field

After [3] airliners.net

[4] uml.edu

After [5] cognisys-inc.com

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Objective

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After [1] (Visbal, 2014)

• Visbal[1] demonstrated leading edge separation bubble, high-frequency excitation delays dynamic stall

– Zero-net-mass-flux blowing/suction – F+ = 50

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Objective

• Confirm the effect of F+ = 50, leading edge, NS-DBD excitation in an experimental pitching airfoil •  Effective control could enhance lift and prevent/

delay dynamic stall

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Methodology

•  ARC at OSU airport is world-class facility with more than 10 wind tunnels from subsonic to supersonic flow regimes •  This project will be conducted in a 2 ft. x 2 ft.

recirculating wind tunnel with Remax ~ 1.2e6 •  This tunnel has previously been used for static stall

and separation control [6,7] (Little et al.)

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Methodology

•  The ARC has expertise in many measurement methods •  Static pressure measurements can resolve

phenomena up to 50 Hz, providing aerodynamic performance data during dynamic stall •  Stereo, phase-locked PIV will allow the dynamic

stall vortex formation and convection to be investigated •  Smoke flow visualization has previously proven

useful to qualitatively visualize flow separation

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Previous Results

•  Previous results demonstrate facility capabilities

[7] Little et al. 2012 9

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Mechanism

•  An oscillating mechanism was designed and built to dynamically vary the angle of attack of the airfoil

– Driven by a computer controlled servo –  Interchangeable windows allow various airfoils (NACA

0015, Boeing VR7, and others)

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Mechanism

• The mechanism design maximizes the optical access to enable stereo-PIV and other optical measurement methods

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Mechanism

•  Preliminary testing of the oscillating mechanism demonstrated it can oscillate at 4 Hz for a 30° range, and 7 Hz for a 10° range • Operational envelope expansion is ongoing

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Summary

• Dynamic stall is a problem encountered in many different application flows •  Investigating control of dynamic stall by high-

frequency (F+ = 50) excitation •  Particularly seeking to confirm and expand

CFD results from Visbal[1] • Mechanism has been designed and tested

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Future Work

• Mechanism operational envelope will be expanded to 10 Hz for 25° oscillation • Characterize baseline dynamic stall with PIV and

static pressure, flow visualization •  Investigate the effect of high-frequency excitation

up to F+ = 50

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References

1.  Visbal, M. "Numerical Exploration of Flow Control for Delay of Dynamic Stall on a Pitching Airfoil," 32nd AIAA Applied Aerodynamics Conference, 2014-2044, (2014)

2.  "LAPD Bell 206 Jetranger" by Mfield - Matthew Field, http://www.photography.mattfield.com - Own work. Licensed under CC BY 2.5 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:LAPD_Bell_206_Jetranger.jpg#/media/File:LAPD_Bell_206_Jetranger.jpg

3.  http://www.airliners.net/photo/USA---Air/Lockheed-Martin-F-22A/1197485/L/

4.  http://www.uml.edu/Images/wind%20turbine_tcm18-88992.jpg

5.  http://www.cognisys-inc.com/how-to/high-speed-shutter/images/11734_Bee-in-Flight-Edit-1000.jpg;

6.  Little, J., M. Nishihara, I. Adamovich, and M. Samimy. "High-Lift Airfoil Trailing Edge Separation Control Using a Single Dielectric Barrier Discharge Plasma Actuator," Experiments in Fluids, Vol. 48, (2010), pp. 521-537.

7.  Little, J., K. Takashima, M. Nishihara, I. Adamovich, and M. Samimy. "Separation Control with Nanosecond-Pulse-Driven Dielectric Barrier Discharge Plasma Actuators," AIAA Journal, Vol. 50, No. 2, (2012), pp. 350-65.

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