Abstract
This contribution relates to the simulation of the flow around the tip of a helicopter rotor blade in hovering flight conditions. We here propose a new methodology of framework adaptation, using a comprehensive rotor code and high-fidelity numerical simulations. We construct an equivalent fixed-wing configuration from a rotating blade, in which centrifugal and Coriolis forces are neglected. The effect of this approximation on the solution is analyzed. The method is validated by a detailed comparison with wind tunnel data from the literature, concerning aerodynamic properties and tip vortex roll-up. This validation also includes variations of the pitch angle and rotational speed, up to transonic tip velocities. Compared to previously published methods of framework adaptation, the new hybrid method is found to reproduce more accurately the flow around a rotating-blade tip.
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Abbreviations
- (r, θ, z):
-
Rotating-blade frame
- (x, y, z):
-
Fixed-wing frame
- (X, Y, Z):
-
Inertial frame
- (δ, n):
-
Sectional frame
- (ξ, η, ζ):
-
Non-inertial frame
- c :
-
Blade chord (m)
- C n :
-
Lift coefficient
- C p :
-
Pressure coefficient
- C t :
-
Thrust coefficient
- M :
-
Mach number
- R :
-
Blade radius (m)
- Ro :
-
Rossby number
- V i :
-
Induced velocity m s−1
- V tip :
-
Tip speed (m s−1)
- ρ :
-
Fluid density (kg m−3)
- ψ :
-
Wake age (°)
- ψ S :
-
Segregation wake age (°)
- Ω:
-
Rotational speed (rpm)
- CT:
-
Caradonna and Tung [1]
- KT:
-
Kocurek and Tangler [2]
- K:
-
Komerath et al. [3]
- S:
-
Srinivasan and McCroskey [4]
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Acknowledgements
The authors thank Michael Le Bars (IRPHE-CNRS) for discussions on the centrifugal and Coriolis forces.
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This paper is based on a presentation at the 41st European Rotorcraft Forum, September 1–4, 2015, Munich, Germany.
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Joulain, A., Desvigne, D., Alfano, D. et al. Numerical investigation of the vortex roll-up from a helicopter blade tip using a novel fixed-wing adaptation method. CEAS Aeronaut J 8, 245–260 (2017). https://doi.org/10.1007/s13272-016-0234-z
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DOI: https://doi.org/10.1007/s13272-016-0234-z