Numerical Simulation Of Dynamic Stall Control On Helicopter Rotor Wings With Variable Droop Leading Edge Method

The dynamic stall, occurred on the retreating blade of rotor wing in helicopter forward flight, produces much negative effect on the speed, load and the control of helicopter. Researchers worldwide quoted several concepts, in order to suppress or eliminate the undesired effect of dynamic stall. VDLE(Variable Droop Leading Edge) is one of the effective methods, however, only validated in 2D calculations and experiments. As the motion of helicopter's rotor wing is more complicate, and the dynamic stall on 2D and 3D varies, the validity of VDLE on rotor wing is discussible. In this thesis, 3D URANS equations are solved and the technology of dynamic & overlap grid is applied, to simulate and control the dynamic stall occurred on the retreating blade of rotor wing in forward flight, with VDLE method. The calculation figures that VDLE restrained the generation and development of dynamic stall, low the power of rotor wing and raise the flight quality.The governing equations, numerical discrete schemes, boundary conditions and turbulence model referred in the thesis. Note that the flow field of flying forward rotor wing is unsteady, the technologies of overlap grid and moving mesh are detailed. Considering the periodicity of the rotor wing's motion, the relationship files for grid overlapping are precalculated, so as to reduce the time for calculationIn order to qualify the solver, the code for unsteady flow is applied, which concludes the"dual time"methods, to simulate the hover of rotor wing with blades untwisted. The results are compared with the experiment's data, to assure the overlap grid generation and its information exchange correct.The main research starts at 2D surging, followed by the description on phenomenon and mechanism of 2D dynamic stall, and the controlling effect of VDLE on dynamic stall. The oscillating of an untwisted blade is also simulated. Analyzing the air force graphs and flow field pictures, the differences between the surging blade and airfoil are expounded, and the interaction of tip flow and dynamic stall is interpreted.Finally, it comes to the numerical simulation of rotor wing in flight forward with the control of VDLE, which mainly under two different conditions. Compared with the uncontrolled case, the application of VDLE in the light stall calculation successfully reduced the power of rotor wing, while causes a slight shrink of the lift; the application of VDLE in the deep stall both successfully reduces the rotor wing and heightens the lift of rotor plate, which shows the VDLE method effective on dynamic stall restrain.