Numerical simulation of rotor-airframe aerodynamic interaction based on unstructured dynamic overset grids

A method of unstructured dynamic overset grids is developed for the numerical simulation of helicopter unsteady rotor-airframe aerodynamic interaction. For the effective treatment of the relative motion between the rotor and the airframe, the domain of flowfield is divided into two overset subzones, namely, a rotational subzone containing the blades and a stationary subzone containing the airframe. The overset part of two subzones is used to convect the flow variables of the two zones. The Taylor series expansion is used to obtain a second-order spatial accuracy, and dual-time stepping is adopted to improve the solution accuracy. Mesh deformation from the blade motion in forward flight is treated by using a spring analogy. Validation is made by numerically simulating the flows around a wind tunnel configuration and comparing the predicted time-averaged and instantaneous inflow and airframe surface pressure distributions with the experimental data. It shows that the present method is efficient and robust for the prediction of complicated unsteady rotor-airframe aerodynamic interaction phenomena.

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