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.

The flow around airfoil is a significant topic due to the complexities associated with separated structures and fluctuating forces. This study investigates flow transition and vortex evolution for a symmetric airfoil within the range of Reynolds number Re=800–2000 and angle of attack AoA=18∘–26∘. A series of numerical simulations are performed using a well-validated level-set based immersed boundary method. The effects of increasing Re and AoA on the near-profile flow and vortex structures are examined comprehensively through various physical results from the time-averaged, time-history and time-resolved perspectives, including lift and drag coefficients, Strouhal number, pressure and friction distributions, portrait phase map, and spectrum of lift coefficient and instantaneous vorticity. Within the adopted parameter space (Re=800–2000 and AoA=18∘–26∘), three distinct flow patterns, namely, single-period & single-amplitude, double-period & double-amplitude, and multi-period & multi-amplitude, are identified based on the time-history and spectrum of the lift coefficient. Comparative analyses reveal that the flow pattern is strongly influenced by both the Reynolds number and the angle of attack. A detailed analysis of these flow patterns is presented through the period time-evolution of the lift coefficient and vortex structures. The results indicate that the mechanisms of flow patterns are closely related to the formation, merging, splitting, and shedding of various vortices.

When a carrier-based aircraft is in arrested landing on deck, the impact loads on landing gears and airframe are closely related to landing states. The distribution and extreme values of the landing loads obtained during life-cycle analysis provide an important basis for buffering parameter design and fatigue design. In this paper, the effect of the multivariate distribution was studied based on military standards and guides. By establishment of a virtual prototype, the extended Fourier amplitude sensitivity test (EFAST) method is applied on sensitivity analysis of landing variables. The results show that sinking speed and rolling angle are the main influencing factors on the landing gear’s course load and vertical load; sinking speed, rolling angle, and yawing angle are the main influencing factors on the landing gear’s lateral load; and sinking speed is the main influencing factor on the barycenter overload. The extreme values of loads show that the typical condition design in the structural strength analysis is safe. The maximum difference value of the vertical load of the main landing gear is 12.0%. This research may provide some reference for structure design of landing gears and compilation of load spectrum for carrier-based aircrafts.