Research on Rotorcraft Blade Tip Vortex Identification and Motion Characteristics in Hovering State

Abstract

The rotorcraft blade tip vortex rolled up by the blade tip when the rotor rotates at high speed will produce a complex induced velocity field, which will have an important impact on the aerodynamic load and performance of the rotor. For this reason, this paper carries out the research on the identification of blade tip vortex and the motion characteristics of the vortex. Through the time-resolved particle image velocimetry (TR-PIV) experiment, the flow field of the rotor at a fixed rotate speed (2100 r/min) with a collective pitch of 6° and 9° was obtained. Based on the vorticity field, Q criterion, and Ω criterion, the research on vortex identification and vortex motion characteristics are realized. The results show that with the increase of blade motion azimuth, the radial position of blade tip vortex gradually contracts inward and the axial position moves downward in hovering state. As the collective pitch of the rotor increases, the radial contraction becomes more obvious, and the axial displacement increases, at the same time, the blade tip vortex intensity increases. Comparative study results show that different vortex identification methods have obtained certain deviations in the vortex center. Compared with other vortex identification methods, the Ω criterion method has a smaller deviation and can accurately identify the vortex core radius and vortex boundary.