A new moving-embedded grid method for numerical simulation of unsteady flow-field of the helicopter rotor in forward flight

Aiming at the key moving-embedded grid approach for predicting the flowfield of helicopter rotor, a new highly efficient method for judging the grid cell relationship has been presented. In this method, the occupied relationship of blade grids among the background grids has been established by calculating the position of special blade grid points among the back-ground grid system, and the method can be used to identify the hole cell among the moving-embedded grid system. Further, the method was extended to establish Inverse Map. Based on the present method, a moving-embedded grid technique has been developed for predicting the flowfield of rotor in forward flight. The effects of background grid and blade grid size on efficiency and reliability have been evaluated respectively by conducting many kinds of rotor test cases in forward flight. Test results showed that the consuming time in constructing the embedded-grid relationship increased slowly with the variable blade grid and background grid size, and it was demonstrated that the present method can satisfy the need for predicting the rotor flowfield in forward flight with good robustness. Finally, the aerodynamic characteristics of the UH-60A rotor in hovering flight and 7A rotor in forward flight have been simulated by the present method with unsteady N-S/Euler solver. By the comparisons of the consuming time by using different hole-cutting approaches and calculated results with experimental data, it was demonstrated that the method can be effective to simulate the unsteady rotor flowfield in forward flight with high-efficiency.