Characterization of the Effect of Helicopter Isolated Blade Vortex on Dynamic Stall

Document Type : Research Article

Authors

1 Department of Aerospace Engineering, Amirkabir University of Technology, Tehran, Iran

2 Department of Aerospace Engineering, Malek Ashtar University of Technology, Tehran, Iran

Abstract

In this research, dynamic stall at sections near the rotor blade tip at a maximum cruise speed of the helicopter with an advanced ratio of 0.35 and cyclic pitching motion, has been studied using computational fluid dynamics simulation. Unsteady Reynolds-averaged Navier–Stokes equations are solved using  model on a domain discretized into a hybrid mesh using finite volume discretization method. Numerical simulation is validated using experimental results of AH1-G helicopter flight tests. Comparison of results indicates that present numerical results match with experimental data well. Dynamic stall occurs as a result of a shock wave in the advancing side which affects the lift coefficient. Interestingly, the effect of the shock wave on the lift coefficient in the regions closer to the blade tip is weakened due to the tip vortex penetration. As a result, few changes are seen in the lift coefficient in these regions in comparison to those of the inner regions of the blade. In addition, the maximum value of lift coefficient in the section closer to the blade tip reduces by 10.2% in comparison to that of the most inner section. Results show that despite the formation of the leading-edge vortex, especially in the inner most sections of the blade, severe dynamic stall does not occur in the retreating side.  In fact, this is due to the weakening of the leading edge vortex by the effect of the radial flow.

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References

[1] T.C. Corke, F.O. Thomas, Dynamic stall in pitching airfoils: aerodynamic damping and compressibility effects, Annual Review of Fluid Mechanics, 47 (2015) 479-505.
[2] A. Brocklehurst, High resolution methods for the aerodynamic design of helicopter rotors, Citeseer, 2013.
[3] N.D. Ham, Aerodynamic loading on a two-dimensional airfoil during dynamic stall, AIAA journal, 6(10) (1968) 1927-1934.
[4] N.D. Ham, M.S. Garelick, Dynamic stall considerations in helicopter rotors, Journal of the American Helicopter Society, 13(2) (1968) 49-55.
[5] W. McCroskey, R. Fisher, Dynamic stall of airfoils and helicopter rotors, AGARD R, 595 (1972) 2.1-2.7.
[6] W.G. Bousman, A qualitative examination of dynamic stall from flight test data, Journal of the American Helicopter Society, 43(4) (1998) 279-295.
[7] M. Potsdam, H. Yeo, W. Johnson, Rotor airloads prediction using loose aerodynamic/structural coupling, Journal of Aircraft, 43(3) (2006) 732-742.
[8] A. Spentzos, G. Barakos, K. Badcock, B. Richards, F. Coton, R.M. Galbraith, E. Berton, D. Favier, Computational fluid dynamics study of three-dimensional dynamic stall of various planform shapes, Journal of Aircraft, 44(4) (2007) 1118-1128.
[9] A. Abhishek, S. Ananthan, J. Baeder, I. Chopra, Prediction and fundamental understanding of stall loads in UH-60A pull-up maneuver, Journal of the American Helicopter Society, 56(4) (2011) 1-14.
[10] A.D. Gardner, K. Richter, Influence of rotation on dynamic stall, Journal of the American Helicopter Society, 58(3) (2013) 1-9.
[11] K. Gharali, D.A. Johnson, Dynamic stall simulation of a pitching airfoil under unsteady freestream velocity, Journal of Fluids and Structures, 42 (2013) 228-244.
[12] A. Zanotti, R. Nilifard, G. Gibertini, A. Guardone, G. Quaranta, Assessment of 2D/3D numerical modeling for deep dynamic stall experiments, Journal of Fluids and Structures, 51 (2014) 97-115.
[13] V. Raghav, N. Komerath, Advance ratio effects on the flow structure and unsteadiness of the dynamic-stall vortex of a rotating blade in steady forward flight, Physics of Fluids, 27(2) (2015) 027101.
[14] J. Letzgus, M. Keßler, E. Krämer, CFD-simulation of three-dimensional dynamic stall on a rotor with cyclic pitch control,  (2015).
[15] C.B. Merz, C. Wolf, K. Richter, K. Kaufmann, A. Mielke, M. Raffel, Spanwise differences in static and dynamic stall on a pitching rotor blade tip model, Journal of the American Helicopter Society, 62(1) (2017) 1-11.
[16] M.R. Visbal, D.J. Garmann, Numerical investigation of spanwise end effects on dynamic stall of a pitching NACA 0012 wing, in:  55th AIAA aerospace sciences meeting, 2017, pp. 1481.
[17] F. Richez, Analysis of dynamic stall mechanisms in helicopter rotor environment, Journal of the American Helicopter Society, 63(2) (2018) 1-11.
[18] Q. Wang, Q. Zhao, Numerical Study on Dynamic-Stall Characteristics of Finite Wing and Rotor, Applied Sciences, 9(3) (2019) 600.
[19] J. Letzgus, M. Keßler, E. Krämer, Simulation of Dynamic Stall on an Elastic Rotor in High-Speed Turn Flight, Journal of the American Helicopter Society, 65(2) (2020) 1-12.
[20] S. Karimian, S. Aramian, A. Abdolahifar, Numerical investigation of dynamic stall reduction on helicopter blade section in forward flight by an airfoil deformation method, Journal of the Brazilian Society of Mechanical Sciences and Engineering, 43(2) (2021) 1-17.
[21] A. Inc, ANSYS FLUENT theory guide (Release 19). Multiphase Flows, in, Ansys Inc, 2017.
[22] J. McNaughton, I. Afgan, D. Apsley, S. Rolfo, T. Stallard, P. Stansby, A simple sliding‐mesh interface procedure and its application to the CFD simulation of a tidal‐stream turbine, International journal for numerical methods in fluids, 74(4) (2014) 250-269.
[23] R. Steijl, G. Barakos, Sliding mesh algorithm for CFD analysis of helicopter rotor–fuselage aerodynamics, International journal for numerical methods in fluids, 58(5) (2008) 527-549.
[24] R. Steijl, G. Barakos, K. Badcock, CFD Analysis of rotor-fuselage aerodynamics based on a sliding mesh algorithm,  (2007).
[25] F.R. Menter, Two-equation eddy-viscosity turbulence models for engineering applications, AIAA journal, 32(8) (1994) 1598-1605.
[26] F. Tejero Embuena, P. Doerffer, O. Szulc, Application of passive flow control device on helicopter rotor blades, Journal of the American Helicopter Society,  (2015).
[27] F.J. Hernandez, Correlation of airloads on a two-bladed helicopter rotor, National Aeronautics and Space Administration, Ames Research Center, 1993.
[28] F. Frey, J. Herb, J. Letzgus, P. Weihing, M. Keßler, E. Krämer, Enhancement and application of the flow solver FLOWer, in:  High Performance Computing in Science and Engineering'18, Springer, 2019, pp. 323-336.
[29] J. Thiemeier, C. Öhrle, F. Frey, M. Keßler, E. Krämer, Aerodynamics and flight mechanics analysis of Airbus Helicopters’ compound helicopter RACER in hover under crosswind conditions, CEAS Aeronautical Journal, 11(1) (2020) 49-66.
[30] G.J. Leishman, Principles of helicopter aerodynamics with CD extra, Cambridge university press, 2006.
[31] J. Jeong, F. Hussain, On the identification of a vortex, Journal of fluid mechanics, 285 (1995) 69-94.
[32] J. DiOttavio, K. Watson, J. Cormey, S. Kondor, N. Komerath, Discrete structures in the radial flow over a rotor blade in dynamic stall, in:  26th AIAA Applied Aerodynamics Conference, 2008, pp. 7344.
Amirkabir Journal of Mechanical Engineering
Volume 54, Issue 1
April 2022
Pages 75-100

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