# Numerical Study of Wave Effect on Aircraft Water-Landing Performance
###### Abstract  
Aircraft, such as amphibious planes, airliners, helicopters and re-entry capsules, are frequently subject to impacting loads from water-landing/ditching on various free surfaces, especially under wave conditions. Understanding and quantifying the water-landing/ditching performance on wave surfaces are of fundamental important for the design and certification of crashworthiness in the field of aerospace engineering. This study aims to numerically assess the effect of wave surface on water-landing process of an amphibious aircraft. The numerical implementation is realized in Reynolds-averaged Navier-Stokes (RANS) framework by combining finite volume method (FVM), volume of fluid (VOF) approach and velocity-inlet wavemaker. The temporal-spatial characteristic of numerical wave and the accuracy of presented model are, respectively, validated by analytical wave and convergence studies. The aircraft landing simulations with different free surface conditions, i.e., calm water, regular wave with different wave heights are then performed and quantitatively compared through several physical parameters, including acceleration, velocity, pressure, pitch angle and free surface deformation. It was found that the aircraft regular wave-landing process experiences several unique stages comparing with the calm-water-landing case. The results clearly confirm that wave surface can influence the aircraft landing performance to a great extent. The fundamental mechanism is found to be that the wave surface slope and wave particle velocity remarkably change the impacting position and effective impacting velocity of the aircraft. a 2022 202  
ditching attempts have been analyzed [1; 5]. Additionally, helicopter crash mishaps occurring due to multiple reasons. Many investigations on helicopter ditching crash have been published [6; 7; 8; 9; 10] and conducted that the probability of experiencing a capsize is highly dependent on the sea state level which depends on the height and period or slope of wave. Summing up, many airline (fixed-wing aircraft) accidents and helicopter mishaps categorized as wave landing/ditching encountered uncontrollable situations and ended in tragedies. Therefore, the assessment of aerodynamics and hydrodynamics performances of aircraft landing/ditching on wave surface are required at the early stage of aircraft design procedure. Particularly, the general features of wave parameter effect on the aircraft landing/ditching process need to be analyzed. There are three methods to address water impacting and landing problems in the literature, including theoretical analysis, experimental test and numerical simulation. A historical review of research related to water impact between 1929 and 2003 can be found in [PERSON] et al. [11] who provides the milestones of research and includes the theoretical and experimental developments. [PERSON] et al. [12] extended significantly on [PERSON]'s review to include researches between 1986 and 2006 by summarizing the major progress on helicopter water impact problem. [PERSON] et al. [4] reviewed earlier developments in the area of aircraft water-landing by NASA Langley Research Center between 1940 and 1975 and concluded the weaknesses of theoretical method and experimental research, respectively. Instead, numerical simulation applications in the field of aircraft water-landing are drawing increasing attention in the academic and industrial communities due to the strengths, e.g., taking into account the complex aircraft configuration and the near field of the surrounding fluids, providing high-resolution results and consuming less money and time. Various numerical results in the field of aircraft calm water-landing/ditching have been published through Arbitrary Lagrangian-Eulerian (ALE) method [13; 14; 15; 16; 17], the massless Smoothed Particle Hydrodynamics (SPH) method [15; 16; 17; 18; 19; 20] and Finite Volume Method (FVM) [4; 21; 22; 23; 24]. Early studies were mainly focused on the feasibility of the ALE and SPH approaches.