Improving numerical simulation of rotor forward flight flow field with unstructured dynamic overset grids

Existing methods for the numerical simulation of rotor forward flight flow field still suffer mainly from two shortcomings: (1) repeatedly establishment for structured dynamic overset grids; (2)searching for donor elements with Inverse Map^[4] is somewhat slow. By using unstructured dynamic overset grids, we can obviate these two shortcomings, thus improving the efficiency and precision of numerical simulation. In the paper, we explain three topics: (1)the motion of blades; (2)unstructured dynamic overset grid system; (3)numerical simulation. The establishment of overset grids, searching for donor elements, data transmission, and linear spring analogy are presented. We explain the fast generation of two overlapping subdomains-rotational area and static area. We also explain why we do not need to repeatedly establish hole map and why we can fast search for donor elements without generating an Inverse Map. We describe the linear spring analogy for treating the flapping and pitching motions of the rotor. The governing equations and the time matching are proposed. We explain solving unsteady Euler equations with an efficient physical time matching technique called dual time matching. Finally we give a numerical simulation example. The simulation results show preliminarily that our calculated results are in fairly good agreement with the test data in the paper by Caradonna et al^[11].