International Journal of Aeronautical and Space Sciences

The Korean Society for Aeronautical and Space Sciences (한국항공우주학회)
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A High-efficiency Trim Method for CFD Numerical Calculation of Helicopter Rotors

  • Ye, Zhou (National Key Laboratory of Science and Technology on Rotorcraft Aeromechanics, PO Box 331, Nanjing University of Aeronautics and Astronautics) ;
  • Xu, Guo-hua (National Key Laboratory of Science and Technology on Rotorcraft Aeromechanics, PO Box 331, Nanjing University of Aeronautics and Astronautics) ;
  • Shi, Yong-jie (National Key Laboratory of Science and Technology on Rotorcraft Aeromechanics, PO Box 331, Nanjing University of Aeronautics and Astronautics) ;
  • Xia, Run-ze (National Key Laboratory of Science and Technology on Rotorcraft Aeromechanics, PO Box 331, Nanjing University of Aeronautics and Astronautics)
  • Received : 2016.06.01
  • Accepted : 2017.05.05
  • Published : 2017.06.30
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Abstract

In order to resolve the trimming difficulty in rotor CFD calculations, a high-efficiency and improved "delta trim method" is established to compute the blade control settings that are necessary to identify the blade motion. In this method, a simplified model which combines the blade element theory and different inflow models is employed to calculate the control settings according to the target aerodynamic forces, then it is coupled into a CFD solver with unsteady Navier-Stokes equations by the delta methodology, which makes the control settings and aerodynamics calculated and updated in the meantime at every trim cycle. Different from the previous work, the current research combines the inflow model based on prescribed wake theory. Using the method established, the control settings and aerodynamic characteristics of Helishape 7A, AH-1G and Caradonna-Tung rotors are calculated. The influence of different inflow models on trimming calculations is analyzed and the computational efficiency of the current "delta trim method" is compared with that of the "CFD-based trim method". Furthermore, for the sake of improving the calculation efficiency, a novel acceleration factor method is introduced to accelerate the trimming process. From the numerical cases, it is demonstrated that the current "delta trim method" has higher computational efficiency than "CFD-based trim method" in both hover and forward flight, and up to 70% of the amount of calculation can be saved by current "delta trim method" which turns out to be satisfactory for engineering applications. In addition, the proposed acceleration factor shows a good ability to accelerate the trim procedure, and the prescribed wake inflow model is always of better stability than other simple inflow models whether the acceleration factor is utilized in trimming calculations.

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References

  1. Bagai, A. and Leishman, J. G., "Rotor Free-Wake Modeling Using A Pseudo-Implicit Relaxation Algorithm", Journal of Aircraft, Vol. 32, No. 6, 1995, pp. 1276-1285. DOI:10.2514/3.46875
  2. Allen, C. B., "Parallel Flow-Solver and Mesh Motion Scheme for Forward Flight Rotor Simulation", Proceedings of the 24th Applied Aerodynamics Conference, San Francisco, California, 2006.
  3. Biava, M., Bindolino, G. and Vigevano, L., "Single Blade Computations of Helicopter Rotors in Forward Flight", Proceedings of the 41st Aerospace Sciences Meeting and Exhibit, Reno, Nevada, 2003.
  4. Yang, Z., Sankar, L. N., Smith, M. J. and Bauchau, O., "Recent Improvements to A Hybrid Method for Rotors in Forward Flight", Journal of Aircraft, Vol. 39, No. 5, 2002, pp. 804-812. DOI:10.2514/2.3000
  5. Chung, K. H., Hwang, C. J., Park, Y. M., Jeon, W. J. and Lee, D. J., "Numerical Predictions of Rotorcraft Unsteady Air- Loadings and BVI Noise by Using A Time-Marching Free- Wake Acoustic Analogy", Proceedings of the 31st European Rotorcraft Forum, Firenze, Italy, 2005.
  6. Kim, J. W., Park, S. H. and Yu, Y. H., "Euler and Navier- Stokes Simulations of Helicopter Rotor Blade in Forward Flight Using An Overlapped Grid Solver", Proceedings of the 19th AIAA Computational Fluid Dynamics, San Antonio, Texas, 2009.
  7. Zhao, J. G. and He, C. J., "A Viscous Vortex Particle Model for Rotor Wake and Interference Analysis", Journal of the American Helicopter Society, Vol. 55, No. 1, 2010, pp. 1-14. DOI:10.4050/JAHS.55.012007
  8. Steijl, R., Barakos, G. N. and Badcock, K. J., "A CFD Framework for Analysis of Helicopter Rotors", Proceedings of the 17th AIAA Computational Fluid Dynamics Conference, Toronto, Canada, 2005.
  9. Bramwell, A., Done, G. and Balmford, D., Bramwell's Helicopter Dynamics 2nd Edition, Butterworth-Heinemann Press, Oxford, 2001.
  10. Drees, J. M., "A Theory of Airflow Through Rotors and its Application to Some Helicopter Problems", Journal of the Helicopter Association of Great Britain, Vol. 3, No. 2, 1949, pp. 79-104.
  11. Leishman, J. G. and Ananthan, S., "Aerodynamic Optimization of A Coaxial Proprotor", Proceedings of the 62th Annual Forum and Technology Display of the American Helicopter Society International, Phoenix, AZ, 2006.
  12. Bagai, A., Contributions to the Mathematical Modeling of Rotor Flowfield Using a Pseudo-Implicit Free-Wake Analysis, University of Maryland Press, Maryland, 1995.
  13. Blazek, J., Computational Fluid Dynamics: Principles and Applications, Second Edition, Elsevier Ltd Press, Oxford, 2005.
  14. Baldwin, B. S. and Lomax, H., "Thin Layer Approximation And Algebraic Model for Separated Turbulent Flows", Proceedings of the AIAA 16th Aerospace Sciences Meeting, Huntsville, Alabama, 1978.
  15. Roe, P. L., "Approximate Riemann Solvers, Parameter Vectors, and Difference Schemes", Journal of Computational Physics, Vol. 43, No. 2, 1981, pp. 357-372. DOI:10.1016/0021- 9991(81)90128-5
  16. Luo, H., Baum, J. D. and Loehner, R., "A Fast, Matrix- Free Implicit Method for Computing Low Mach Number Flows on Unstructured Grids", International Journal of Computational Fluid Dynamics, Vol. 14, No. 2, 2000, pp. 133- 157. DOI:10.2514/6.1999-3315
  17. Chiu, I. T. and Meakin, R. L., "On Automating Domain Connectivity for Overset Grids", Proceedings of the 33rd Aerospace Sciences Meeting & Exhibit, Reno, NV, 1995.
  18. Lohner, R., Sharov, D., Luo, H. and Ramamurti, R., "Overlapping Unstructured Grid", Proceedings of the 39th AIAA Aerospace Sciences Meeting & Exhibit, Reno, NV, 2001.
  19. Renzoni, P., D'Alascio, A., Kroll, N., Peshkin, D., Hounjet, M. H., Boniface, J. C. and Schöll, E., "EROS-A Common European Euler Code for the Analysis of the Helicopter Rotor Flowfield", Progress in Aerospace Science, Vol. 36, No. 5, 2000, pp. 437-485. DOI: 10.1016/S0376- 0421(00)00006-3
  20. Lebel, G., Benoit, B., Dufour, R. and Jacquet- Richardet, G., "Aerodynamic and Dynamic Models for Rotor Load Prediction - Application to New Generation Blades", Proceedings of the 67th Annual Forum of the American Helicopter Society, Virginia Beach, VA, 2011.
  21. Cross, J. F. and Tu, W., "Tabulation of Data from the Tip Aerodynamics and Acoustics Test", Proceedings of the 1990 NASA Technical Memorandum, Cupertino, California, 1990.