Airfoil Optimization of Wing-in-Ground Craft Considering Anti-waves Ability

The WIG (Wing-in-Ground) craft is a novel vehicle that makes use of the ground effect to realize cruising above the water. Under the influence of ocean waves, the wing may experience lift oscillation, posing a risk to its flight safety. However, there are few researches on aerodynamic design of WIG crafts considering lift oscillation. The objective of this paper is to explore the main factors affecting the lift oscillation of WIG airfoil, find out a way to reduce the lift oscillation, and then carry out the airfoil design optimization to achieve the maximization of lift and minimization of drag, subject to the constraints of lift oscillation. First, simulation of a NACA23012 airfoil using the Volume of Fluid (VOF) method is used to simulate the periodically fluctuating water surface. An efficient global surrogate-based optimization algorithm is used for low lift oscillation design to improve anti-waves ability. Result shows that the leading edge of the upper surface has a major impact on the lift oscillation. The optimized airfoil obtains a 12% reduction in lift oscillation by reducing the strength of the low-pressure area at the leading edge. Second, on the basis of above research, the airfoil design subject to lift oscillation constraint is carried out to increase lift and reduce drag. The results show that the strength of the low-pressure area of the optimized airfoil is reduced, and the designed airfoil achieves 8.4% increase in lift-to-drag ratio as well as 8.5% reduction in lift oscillation, compared to the baseline airfoil.