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A coupled prescribed wake-Euler solver for efficient computing helicopter rotor flows in hover

Hejranfar, K ; Sharif University of Technology | 2006

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  1. Type of Document: Article
  2. Publisher: Curran Associates Inc , 2006
  3. Abstract:
  4. A numerical solution technique is developed to simulate the flowfield of hovering helicopter rotor. The present method uses a coupled prescribed wake-Euler solver to efficiently allow the vortical wake effects. The threedimensional Euler equations written in a rotating coordinate frame are solved by using a cell-centered finite volume scheme that is based on the Roe's flux-difference splitting on unstructured meshes. High-order accuracy is achieved via the reconstruction of flow variables using the MUSCL interpolation technique. Calculations are carried out for an isolated rotor in hover for two operating conditions of subsonic and transonic tip Mach numbers, Mtip = 0.44 and Mtip = 0.877 , and the collective pitch angle θc = 8° (the Caradona and Tung test cases). The computed surface pressure distributions for each case are compared with available numerical and experimental data. The results indicate that for conventional grids, the calculated surface pressure distributions do not agree with the experimental data especially at inboard sections of the blades. This difference may be due to the fact that the numerical methods using course grids have inherent numerical dissipation which can affect the structure of the rotor wake. To improve the computed results, a perturbation method is used and wake effects are modeled using only a tip vortex trailed from the tip of each blade. The resulting surface pressure distributions using the proposed technique exhibit good agreement with the numerical and experimental results, especially for the subsonic case
  5. Keywords:
  6. Aerodynamics ; Pressure distribution ; Flux difference splitting ; Interpolation techniques ; Perturbation method ; Prescribed wake ; Rotor flows ; Surface pressure distribution ; Three-dimensional Euler equations ; Unstructured grid ; Wakes
  7. Source: 25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, 3 September 2006 through 8 September 2006 ; Volume 3 , 2006 , Pages 1670-1681
  8. URL: http://www.icas.org/ICAS_ARCHIVE/ICAS2006/PAPERS/661.PDF