Abstract
To study the three-dimensional effects on the dynamic-stall characteristics of a rotor blade, the unsteady flowfields of the finite wing and rotor were simulated under dynamic-stall conditions, respectively. Unsteady Reynolds-averaged Navier–Stokes (URANS) equations coupled with a third-order Roe–MUSCL spatial discretization scheme were chosen as the governing equations to predict the three-dimensional flowfields. It is indicated from the simulated results of a finite wing that dynamic stall would be restricted near the wing tip due to the influence of the wing-tip vortex. By comparing the simulated results of the finite wing with the spanwise flow, it is indicated that the spanwise flow would arouse vortex accumulation. Consequently, the dynamic stall is restricted near the wing root and aggravated near the wing tip. By comparing the simulated results of a rotor in forward flight, it is indicated that the dynamic stall of the rotor would be inhibited due to the effects of the spanwise flow and Coriolis force. This work fills the gap regarding the insufficient three-dimensional dynamic stall of a helicopter rotor, and could be used to guide rotor airfoil shape design in the future.
Highlights
To satisfy the flight requirements of a helicopter in forward flight, rotor blades are designed to perform pitching, flapping, and rotation movements
Rotor blades work in unsteady aerodynamic environments compared with a fixed-wing aircraft
This study indicated that the Differential Infrared Thermography (DIF) method could differentiate the stalled and attached flow with no contacted-blade surface treatment
Summary
To satisfy the flight requirements of a helicopter in forward flight, rotor blades are designed to perform pitching, flapping, and rotation movements. The aerodynamic characteristics of helicopter rotor are much more complex, and the dynamic-stall phenomenon [1,2]. Some studies on the three-dimensional (3D) dynamic-stall characteristics of a finite wing or rotor were done by employing experiment and numerical methods. By employing CFD, a numerical study about the 3D dynamic stall of a wing with an NACA0015 airfoil was performed by Salari [19]. Raghav [22] investigated the dynamic-stall characteristics of a rotor in forward flight by employing an experimental and a computational method, and this research captured the radial-jet layer caused by radial acceleration. In order to obtain a deeper understanding of these 3D effects on dynamic stall, the unsteady aerodynamic characteristics of a finite wing are studied under spanwise flow and nonspanwise flow by using the URANS CFD method. A study on unsteady aerodynamic characteristics of a rotor in forward flight was performed
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