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EULER Code for Helicopter Rotors

EULER Code for Helicopter Rotors. EROS - European Rotorcraft Software. Romuald Morvant March 2001. PLAN. 1- Presentation of the EROS project 2- The numerical SCHEMES 3- FUN & UNFACtored methods - RESULTS 4- CONCLUSIONS 5- FUTURE WORK. OBJECTIVES. Accurate prediction of the

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EULER Code for Helicopter Rotors

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  1. EULER Code for Helicopter Rotors EROS - European Rotorcraft Software Romuald Morvant March 2001

  2. PLAN • 1- Presentation of the EROS project • 2- The numerical SCHEMES • 3- FUN & UNFACtored methods - RESULTS • 4- CONCLUSIONS • 5- FUTURE WORK

  3. OBJECTIVES Accurate prediction of the Aerodynamic Load distribution along the blades. 1- Reduce pilot control-loads 2- Increase speed 3- Identify and quantify the aerodynamic noise sources

  4. GEROS - GRID GENERATOR Adapted for Multi-blade calculations Various topologies in the framework of CHIMERA overlapping grids

  5. EROS - INVISCID EULER solver • A- Cell-centred FINITE VOLUME method • B- SPATIAL discretisation scheme • C- DUAL-TIME implicit scheme • D- TIME-STEPPING scheme

  6. Finite volume method • 1- Closed surface • 2- Rigid motion of the blade • 3- Geometric Conservation Law

  7. Calculations of the surface fluxes

  8. IMPLICIT DUAL-TIME METHOD Time discretisation Spatial discretisation Redefinition of the Residual term

  9. Time-stepping SCHEME • 1- Multi-stage • Runge-Kutta scheme • 2- Unfactored-factored • method • Use of acceleration techniques • CFL number

  10. RESULTS from previous reports • Ö JAMESON - Runge-Kutta • Ö ROE - FUN method • Preference for the ROE-FUN method: • - BETTER respect of the physic (convection) • - FASTER convergence

  11. FUN METHOD • Factorisation in the spanwise direction 2 LINEAR SYSTEMS

  12. ANALYSES of the FUN method • Ö SMALL SIZE of the matrices • ´ LARGE NUMBER of pseudo-time steps • to get a high convergence. • Problems to damp out the small • errors frequencies

  13. Objectif: SPEED the code UP 1- CODING 2- ALGORITHM UNFACtored method

  14. CODING • UNROLLING of repetitive operations • Transformation of the matrices (5x5) • into a vector (25x1)

  15. Implementation of the UNFACtored method • Modification of the LHS block matrix size • where the flow variables are stored • Consideration of the 3 Dimensions ALGORITHM

  16. REFERENCE TESTS - LANN WING : unsteady case (3D) - EC/ONERA 7A 4-bladed Model Rotor Model Rotor in transonic hover flight Single block grid

  17. UNSTEADY Case - LANN wing Pitching moment coeff. Sectional Force Coefficients y/b=0.475 y/b=0.825

  18. UNSTEADY Case - LANN wing Mean Steady Pressure First Harmonic Pressure y/b=0.475 y/b=0.825

  19. Convergence behaviour STEADY run UNSTEADY run

  20. 7A Model Rotor in hover flight Periodic OH grid, 84 x 60 x 32

  21. 7A Model Rotor in hover flight Pressure Coefficient distribution, Normal force Coeff.

  22. CONVERGENCE Behaviour

  23. COMMENTARIES • UNFACtored method • Ö Higher CFL number • Ö Faster convergence • Higher average computing time / iterations

  24. FINAL RESULTS

  25. CONCLUSIONS • Ö GOOD agreement with the FUN method • Ö Calculations 5 times faster • This method requires some other tests. • It looks ATTRACTIVE for the unsteady cases

  26. FUTURE WORK • Use of the UNFACtored method for the • CHIMERA grid • Implementation of the WENO method relevant • to a future AEROACOUSTIC module: • Blade Vortex Interaction (BVI) • MPI implementation to enable the studies of • large and important cases.

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