Research On Rotor Dynamic Wake Model Based On Vortex Ring Elements With Multiple Degrees Of Freedom

Real-time flight simulation is an effective approach for helicopter maneuvering flight research, which requires the employed helicopter mathematical model not only have high accuracy during the maneuvering flight, but also have rapid and real-time computational efficiency. For this need, A new rotor dynamic wake model based on multi-degree of freedom vortex ring elements is presented and some related verification and applied research has been conducted. Vortex ring elements which have 7 degrees of freedom are used to represent the rotor wake vortices. The proposed model can describe dynamic distortion behaviors of rotor wakes during large maneuvering flight, and give transient induced velocity distribution of rotor wake in the rotor disk or any area of the space, which has important application value for of helicopter maneuvering flight research.The first chapter, as the background, the rotor inflow / wake model research literatures are briefly introduced, and pointed out that the generality and computational efficiency of the existed models still can't fully meet the requirements of the engineering application.The second chapter, a rotor wake model with vortex ring elements is proposed; The motion and generation model but also the vortex core diffusion model of vortex ring elements is presented; A numerical stable time step algorithm for vortex ring elements is developed;A fast calculation method for vortex ring elements is proposed.The third chapter, some example is presented to preliminarily verify the correctness and computational efficiency of the proposed model. Vortex ring elements wake model is extended to both a single rotor wake model including internal vortex wake and a coaxial rotor wake, and the models are verified by the experimental data.The forth chapter, a rotor unsteady aerodynamic model is proposed by combination with vortex ring elements wake model, blade flapping motion equation, and airfoil unsteady aerodynamic model. Some examples are chosen to research the rotor unsteady aerodynamics in maneuvering flight.The fifth chapter, vortex ring elements wake model is coupled with the existing dynamics flight model. By comparisons with the flight test data, it shows that the proposed rotor wake model has high accuracy and can correctly calculate the off-axis responses in pitch / roll maneuvering flight.