Numerical investigation on the resistance characteristics of a flying boat planing in calm water

Abstract

Recently, there has been an increasing interest in unmanned flying boats for their wide applications in military and civil fields. The planing resistance characteristics are the primary concern in the design of a flying boat, but the related numerical researches have been rarely published. This paper proposes a decoupling numerical model to investigate the planing resistance characteristics of a flying boat combining the analysis of aerodynamics and hydrodynamics. The numerical model was validated with open-water planing tests conducted at speeds ranging from FrB=1.25 to FrB=8.77, and the mean error in the trim angle and resistance are 8.7% and 10.5%, respectively. The numerical results evidence that the hydrodynamic resistance plays the dominant role in total resistance but would be notably affected by the aerodynamic lift and pitching moment at high speeds. The hydrodynamic analysis on the flying boat reveals that during the pre-planing stage the hydrodynamic pressure force acting on afterbody could provide a forward component, which improves the hydrodynamic resistance characteristics. Additionally, the investigation on the formation of air cavity emphasizes the importance of sufficient air supply for maintaining the air cavity, or the cavity might be choked with water resulting in a sudden increase of hydrodynamic pressure resistance. This study would give a better understanding of the hydrodynamic mechanism of flying boats and provide guidance for the integrated design of aerodynamics and hydrodynamics of flying boats.