Development of an Unsteady Aerodynamic Analysis Module for Rotor Comprehensive Analysis Code

  • Published : 2009.11.30


The inherent aeromechanical complexity of a rotor system necessitated the comprehensive analysis code for helicopter rotor system. In the present study, an aerodynamic analysis module has been developed as a part of rotorcraft comprehensive program. Aerodynamic analysis module is largely classified into airload calculation routine and inflow analysis routine. For airload calculation, quasi-steady analysis model is employed based on the blade element method with the correction of unsteady aerodynamic effects. In order to take unsteady effects - body motion effects and dynamic stall - into account, aerodynamic coefficients are corrected by considering Leishman-Beddoes's unsteady model. Various inflow models and vortex wake models are implemented in the aerodynamic module to consider wake induced inflow. Specifically, linear inflow, dynamic inflow, prescribed wake and free wake model are integrated into the present module. The aerodynamic characteristics of each method are compared and validated against available experimental data such as Elliot's induced inflow distribution and sectional normal force coefficients of AH-1G. In order to validate unsteady aerodynamic model, 2-D unsteady model for NACA0012 airfoil is validated against aerodynamic coefficients of McAlister's experimental data.


Linear Inflow;Dynamic Inflow;Prescribed Wake;Free Wake;Blade Element Method;Unsteady Effect


  1. J. G. Leishman, "Principle of Helicopter Aerodynamics 2nd Edition", Cambridge University Press, 2006.
  2. J. G. Leishman, T. S. Beddoes, "A Generalized Model for Airfoil Unsteady Aerodynamic Behavior and Dynamic Stall Using the Indicial Method", Proceedings of the 42nd Annual Forum of the American Helicopter Society, Washington D.C., June 1986.
  3. G. S. Bir, I. Chopra and et al., “University of Maryland Advanced Rotorcraft Code(UMARC) Theory Manual", Technical Report UM-AERO 94-18, Center for Rotorcraft Education and Research, University of Maryland, College Park, July 1994.
  4. C. J. He, "Development and Application of a Generalized Dynamic Wake Theory for Lifting Rotors", Doctor Thesis, Georgia Institute of Technology, 1989.
  5. D. A. Peters and C. J. He, "Finite State Induced Flow Models Part II : Three- Dimensional Rotor Disk", Journal of Aircraft, Vol. 32, No. 2, 1995, pp. 323-333.
  6. Z. Yang, L. N. Sankar, M. J. Smith and O. Bauchau, "Recent Improvements to a Hybrid Method for Rotors in Forward Flight", Journal of Aircraft, Vol. 39, No. 5, Sep.-Oct., 2002, pp. 804-812.
  7. N. M. Komerath and O. A. Schreiber, "Implementation and Validation of a Wake Model for Low-Speed Forward Flight", Final Report, NASA Grant NAG-1-693, Sep., 1987.
  8. J. Lee, K. Yee and S. Oh, "Numerical Investigation of Dual Rotors Using a Time- Marching Free-Wake Method", Proc. Of American Helicopter Society 64th Annual Forum, Montreal, Canada, April 29-May 1, 2008.
  9. J. W. Elliot, S. L. Althoff and R. H. Sailey, "Inflow Measurement Made with a Laser Velocimeter on a Helicopter Model in Forward Flight-$\mu$=0.15", NASA TM 100541, 1988.
  10. K. W. McAlister and L. W. Carr, "Water Tunnel Experiments on an Oscillating Airfoil", NASA TM 78446, 1976.
  11. G. H. Vatistas, V. Kozel and W. Mih, "A Simpler Model for Concentrated Vortices", Experiments in Fluids, Vol. 11, 1991, pp. 73-76.
  12. H. B. Squire, "The Growth of a Vortex in Turbulent Flow", Aeronautical Quarterly, Vol. 16, Aug. 1965, pp. 302-306.
  13. R. C. Baker and B. Charlie, “Nonlinear unstable systems", International Journal of Control, Vol. 23, No. 4, 1989, pp. 123-145.

Cited by

  1. Aeroelastic Analysis of a Hingeless Rotor Using a Dynamic Wake Model vol.48, pp.5, 2011,
  2. The impact of yaw error on aeroelastic characteristics of a horizontal axis wind turbine blade vol.60, 2013,