Impact of Reduced Frequency on Pressure Distribution on the Lower Surface of a Supercritical Airfoil in Pitch-Pause-Return-Motion

Document Type : Research Article

Authors

1 Azad university

2 Department of MEchanical and Aerospace Eng., Schience and Research Branch, Azad University

3 Sharif university

Abstract

Effects of reduced frequency, pause duration and stop angle on pressure distribution   on the lower surface of a thin supercritical airfoil undergoing the pitch-pause-return maneuver have been studied. The experiments have been performed in a subsonic wind tunnel for a fixed mean angle of attack and at a constant amplitude. The reduced frequencies were from 0.01 to 0.12, and three stop angles were chosen during upstroke motion in below stall, near stall and post-stall regions. For all angles of attack below the static stall, the pressure distributions are nearly identical at the rear quarter chord on the lower surface. For beyond the stall angles, the lower surface pressure distributions are observed to remain unchanged from the leading edge downstream to x⁄c=0.15. Also, dynamic results show that the behavior of pressure distribution at the lower surface taps for all stop angles, reduced frequencies and pause durations, are identical from the leading edge to x⁄c=0.70 and are higher than the static values at zero angle of attack. However, the lower surface pressure distributions have been observed to be entirely different at the rear %30 chord for various pause angles, which can be deemed to be the signature of the unsteady Gortler vortices.

Keywords

Main Subjects

References

[1]  J. D. Eldredge, C. J. Wang, M. V. Ol, A Computational Study of a Canonical Pitch-up, Pitch-down Wing Maneuver, 39th AIAA Fluid Dynamic conference, San Antonio, Texas, (2009) 3687.
[2]  M. V. Ol, A. Altman, J. D. Eldredge, D. J. Garmann, Y. Lian, Resume of the AIAA FDTC Low Reynolds Number Discussion Groups Canonical Cases, 48th AIAA Aerospace Science Meeting, rlando, Florida, (2010) 1085.
[3] W. B. Herbst, Future Fighter Technologies, Journal of Aircraft, 17(8) (1980) 561-566.
[4] J. M. Walker, H. E. Helin, J. H. Strickland, An Experimental Investigation of an Airfoil Undergoing Large-Amplitude Pitching Motions, AIAA Journal, 23(8) (1985) 1141-1142.
[5] M. R. Visbal, J. S. Shang, Investigation of the Flow Structure around a Rapidly Pitching Airfoil, AIAA Journal, 28 (1989) 1044-1051.
[6] M. Akbari, S. Price, Simulation of dynamic stall for      a Naca 0012 airfoil using a vortex method, Journal of Fluids and Structures, 17 (2003) 855–874.
[7]  K. Ramesh, A. Gopalarathnam, J. R. Edvards, M.V. Ol, K. Granlund, Theoretical, Computational and Experimental Studies of a Flat Plate Undergoing High- Amplitude Pitching Motion, 43th AIAA Fluid Dynamic conference, San Diego, 2013.
[8] H. Te Yu, L. P.  Bernal, C. Morrison, Experimental Investigation of Pitch Ramp-Hold-Return Motion of Flat Plates at Low Reynolds Number, 50th AIAA Aerospace Science Meeting, Nashville, Tennessee, (2012) 51.
[9] H. Te Yu, Unsteady Aerodynamics of Pitching Flat Plate Wings [dissertation], Central Michigan University, 2014.
[10] C. D. Harris, NASA Supercritical Airfoil, A Matrix of Family-Related Airfoils, NASA Technical Paper, (1990) 2969
[11] A. Golestani, M. B. Ehghaghi Bonab, M. R. Soltani, An Experimental Study of Buffet Detection on Supercritical Airfoil in Transonic Regime, Journal of Aerospace Engineering, 229(2) (2015) 312-322.
[12] A. A. Haghiri, M. Mani, N. Fallahpour, Unsteady Boundary Layer Measurment on an Osilating (Pitching) Supercritical Airfoil in Compressible Flow Using Multiple Hot-Film Sensors, Journal of Aerospace Engineering, 229(10) (2015) 1771-1784.
[13] Z. Eslami Haghighat, Ali R. Davari, M. R. Soltani, Impact of Reduced Frequency on  the  Time  Lag  in  the Pressure Distribution over  a  Supercritical  Airfoil in a Pitch-Pause-Return Motion, Chinese Journal of Aeronautics, 32(2) (2019) 243-252.
[14] J. M. Floryan, W. S. Saric, Stability of Gortler Vortices in Boundary Layers, AIAA Journal, 20(3) (1979) 316- 324.
[15] W. S. Saric, Gortler Vortices, Annual Reviews, Fluid Mechanic, 26 (1994) 379-409.
[16] K. Granlund, M. V. Ol, Experiment on Pitching Plates, Force and Flowfield Measurement at Low Reynolds Number, 49th AIAA Aerospace Science Meeting, Orlando, Florida, (2011) 872.
[17] W. J. McCroskey, L. W. Carr, K. W. McAlister, Dynamic Stall Experiments on Oscillating Airfoils, AIAA Journal, 14(1) (1976) 57-68.
[18] W. Geissler, G. Dietz, H. Mai, Dynamic Stall on Supercritical Airfoil, Aerospace Science and Technology, 9(5) (2005) 390-399.
[19] C. Shih, L. Lourenco, L. V. Dommelen, A. KrotHapalli, Unsteady Flow Past an Airfoil Pitching at a Constant Rate, AIAA Journal, 30(5) (1992) 1153-1161.
Amirkabir Journal of Mechanical Engineering
Volume 52, Issue 4
July 2020
Pages 971-984

Files

Share

How to cite

Statistics