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Numerical Investigation on Aerodynamic Performance and Interaction of a Lift-Offset Coaxial Rotor in Forward Flight

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Abstract

A numerical method based on Reynolds Averaged Navier–Stokes (RANS) equations and moving overset mesh technique is developed to simulate the unsteady flow field of a rigid coaxial rotor. A high-efficient hybrid trim model is adopted to ensure the simulation accuracy of lift-offset (LOS). Cases in different advance ratios are trimmed for constant thrust coefficient and torque-balance. The effects of LOS, rotor spacing and RPM on the aerodynamic performance and interaction are analyzed. Results show that, in forward flight the lift–drag ratio can be improved by appropriate LOS. The rotor drag increases with LOS, as there is also a corresponding offset of drag. The optimum LOS varies with flight speed. At large advance ratio the interactions of the coaxial rotor are much weak, except the blade–meeting interaction. The interaction is typically illustrated by the impulsive loads of the upper blade at retreating side (270°), as the flow field is dominated by the advancing blade (90°) of the lower rotor. The interaction intensity is sensitive to LOS, rotor spacing and RPM, as it depends on the flow field gradient induced by the lower blade acting on the upper blade.

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Abbreviations

c:

Blade chord

C T, C Q :

Rotor thrust and torque coefficient

C L, C D :

Rotor lift and drag coefficient

Cl:

Blade sectional lift coefficient

C p :

Pressure coefficient

\(\mu \) :

Rotor advance ratio

Matip :

Rotor tip Mach number in hover

R:

Rotor radius

\({\theta }_{0},{\theta }_{1s}{,\theta }_{1c}\) :

Collective, lateral cyclic, and longitudinal cyclic pitch angles

S1, U1, L1:

One blade of the single, upper and lower rotors

L:

Lower rotor

U:

Upper rotor

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 12102154), and the Foundation of Key Laboratory of Aerodynamic Noise Control (No. ANCL20200203).

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Authors and Affiliations

  1. Institute for Energy Research, Jiangsu University, Zhenjiang, 212013, China

    Haotian Qi, Ping Wang & Linsong Jiang

  2. Key Laboratory of Aerodynamic Noise Control, China Aerodynamics Research and Development Center, Mianyang, 621000, China

    Haotian Qi

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  1. Haotian Qi
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  2. Ping Wang
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  3. Linsong Jiang
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Correspondence to Haotian Qi or Ping Wang.

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Qi, H., Wang, P. & Jiang, L. Numerical Investigation on Aerodynamic Performance and Interaction of a Lift-Offset Coaxial Rotor in Forward Flight. Int. J. Aeronaut. Space Sci. 23, 255–264 (2022). https://doi.org/10.1007/s42405-022-00444-9

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  • DOI: https://doi.org/10.1007/s42405-022-00444-9

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