Investigation on unsteady aerodynamics of rotor in the vortex ring state
Research on the rationality of rotor in the vortex ring state is of significant importance for helicopter flight safety.Based on the Reynolds-averaged Navier-Stokes control equations,the sliding mesh technique,unstructured mesh modeling and the Spalart-Allmaras turbulence model,rotor en-countering the vortex ring state in vertical flights with different descent rates was simulated.Firstly,the wind tunnel experimental data of the rotor in vortex ring states were verified.Then the aerody-namic parameters of the rotor in the deep vortex ring state were analyzed.It was found that the span-wise aerodynamic force between propellers has a non-synchronous periodic change.Finally,the rotor aerodynamic changes under different descent rates were compared.The research results show that the vortex ring will cause significant thrust loss at the front end of the rotor blade,while the thrust at the rear end of the rotor will increase slightly.An analytic idea is provided for the rotor encountering vortex ring state in this paper,which has certain practical significance for guiding the rotor shape de-sign.
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