Efficient Decoupled Hydrodynamic and Aerodynamic Analysis of Amphibious Aircraft Water Takeoff Process

This paper proposes a framework to analyze the takeoff process of amphibious aircraft using decoupled hydrodynamic and aerodynamic numerical methods. The approach combines a volume-of-fluid calculation for the boat shape using FLUENT and a separate Reynolds-averaged Navier-Stokes calculation using ANSYS/CFX for the wing-body configuration. The two separated calculations are repeated for every time step during takeoff, and steady calculations are assumed for each time step. The waterline is updated for each time step using calculations of flight mechanics based on engine data and hydrodynamic and aerodynamic results obtained. In addition, to improve the efficiency of the method, a drag breakdown method is adopted to replace the time-consuming viscous calculations. In the method, the frictional drag is calculated based on flat-plate theory, and wave resistance is computed using the inviscid model. The new method can achieve an accuracy of within 5% of those using fully viscous calculations, while halving the computing time. The method is applied in the analysis of a typical amphibious aircraft takeoff process and can be used in further optimizations of the amphibious configuration.