Efficient Multiobjective Optimization of Amphibious Aircraft Fuselage Steps with Decoupled Hydrodynamic and Aerodynamic Analysis Models

This paper proposes an efficient framework for multiobjective optimization of the fuselage step on a large amphibious aircraft using a combination of computational aerodynamic and hydrodynamic methods. Both cruise drag and water take-off resistance and distance are calculated to evaluate the effects of the two key parameters, the longitudinal location and the depth of the step. A Reynolds-averaged Navier-Stokes (RANS) model was used for the calculation of cruise drag of the wing body configuration. Water take-off resistance and distance required for the baseline configuration were calculated using a volume of fluid method for hydrodynamic calculation and RANS method for aerodynamic calculation, respectively. A drag breakdown method was adopted to improve the efficiency of the hydraulic calculations. The method can achieve an accuracy of less than 5% difference compared to fully viscous calculations with only half of the computational time. The optimization is achieved using a combination of design of experiment and the response surfaces method. The optimized step configuration achieved an 18% improvement in take-off distance while maintaining similar cruise performance. The proposed method is generic and can be used in the optimizations of other components such as wings and fuselage geometries of amphibious aircraft. (C) 2015 American Society of Civil Engineers.