EULER Code for Helicopter Rotors

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

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GEROS - GRID GENERATOR

• Adapted for Multi-blade calculations
• Various topologies in the framework of
• CHIMERA overlapping grids

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EROS - INVISCID EULER solver
A- Cell-centred FINITE VOLUME
method B- SPATIAL discretisation scheme
C- DUAL-TIME implicit scheme D-
TIME-STEPPING scheme
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Finite volume method
1- Closed surface 2- Rigid motion of the
blade 3- Geometric Conservation Law
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Calculations of the surface fluxes
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IMPLICIT DUAL-TIME METHOD
Time discretisation
Spatial discretisation
Redefinition of the Residual term
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Time-stepping SCHEME
1- Multi-stage Runge-Kutta scheme
2- Unfactored-factored method
Use of acceleration techniques CFL number
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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
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FUN METHOD
Factorisation in the spanwise direction
2 LINEAR SYSTEMS
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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
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Objectif SPEED the code UP

• 1- CODING
• 2- ALGORITHM
• UNFACtored method

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CODING
UNROLLING of repetitive operations Transformation
of the matrices (5x5) into a vector (25x1)
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ALGORITHM
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REFERENCE TESTS

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

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UNSTEADY Case - LANN wing
Pitching moment coeff.
Sectional Force Coefficients
y/b0.475
y/b0.825
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UNSTEADY Case - LANN wing
Mean Steady Pressure
First Harmonic Pressure
y/b0.475
y/b0.825
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Convergence behaviour
STEADY run
UNSTEADY run
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7A Model Rotor in hover flight
Periodic OH grid, 84 x 60 x 32
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7A Model Rotor in hover flight
Pressure Coefficient distribution, Normal force
Coeff.
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CONVERGENCE Behaviour
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COMMENTARIES
UNFACtored method Ö Higher CFL
number Ö Faster convergence Higher
average computing time / iterations
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FINAL RESULTS
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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
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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.