Rotor Wake Measurements For A Rotor In Forward Flight

In order to have a better knowledge of the flowfield around an helicopter blade in forward flight and to obtain data for comparison with new inflow models, laser measurements of the velocity components in the vicinity of the rotor disc and in the wake have been performed. Three-dimensional measurements can be performed with the laser Doppler velocimeter used in these experiments but most of the results shown here, were obtained in two-dimensional ; some of them in backscattered mode and others in forward scattered mode. This paper presents the main experimental results obtained in different vertical planes of the advancing blade side for a three-blade rotor. In particular the azimuthal evolutions of the tangential and vertical velocity components and the trajectory of the tip vortex, in the vertical plane Ψ = 90° are studied.