Performance and Wake Analysis of Rotors in Axial Flight Using Computational Fluid Dynamics

Abstract

Flow field around rotors in axial flight is known to be complex especially in steep descent where the rotor is operating inside its own wake. It is often reported that, in this flight condition, the rotor is susceptible to severe wake interactions causing unsteady blade load, severe vibration, loss of performance, as well as poor control and handling. So far, there is little data from experimental and numerical analysis available for rotors in axial flight. In this paper, the steady Reynolds-Averaged Navier-Stokes Computational Fluid Dynamics solver Helicopter Multi-Block was used to predict the performance of rotors in axial flight. The main objective of this study was to improve the basic knowledge about the subject and to validate the flow solver used. The results obtained are presented in the form of surface pressure, rotor performance parameters, and vortex wake trajectories. The detailed velocity field of the tip vortex for a rotor in hover was also investigated, and a strong self-similarity of the swirl velocity profile was found. The predicted results obtained when compared with available experimental data showed a reasonably agreement for hover and descent rate, suggesting unsteady solution for rotors in vortex-ring state.

Dynamic Modeling and Analysis of Tilt-Wing Electric Vertical Take-Off and Landing Vehicles

“…In order to evaluate the accuracy of the rotor model, it is compared to the results from CFD simulations in Fig. 4, found in [68]. The authors analysed the performance and wake of the famous Caradonna Tung rotor, that is often used as validation case for CFD-based rotor investigations.…”

“…Fig. 4 Comparison of the rotor model with CFD references of a Caradonna Tung rotor in vertical ascent[68] …”