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 present study proposes a pseudorotation adjoint-based aerodynamic and aeroacoustic optimization method for the application on isolated rotors with both accuracy and efficiency. The pseudorotation adjoint-based optimization methodology incorporates two innovative techniques: i) a hybrid computational fluid dynamics–computational aeroacoustics method closely integrating with Reynolds-averaged Navier–Stokes equations under a rotating reference frame within a pseudorotation moving-medium Ffowcs Williams-Hawkings formulation to evaluate aerodynamic performance and tonal noise, and ii) a unified architecture for steady-state adjoint-based sensitivity analyses of both aerodynamics and aeroacoustics leveraging the pseudorotation approach, thereby facilitating effective multi-objective weighted optimizations within one comprehensive framework. The proposed pseudorotation steady adjoint-based optimization method is applied to a bidiscipline optimization problem of rotor blades compared with our previous on-the-fly unsteady adjoint method. Results of the comparative study demonstrate that the pseudorotation steady approach exhibits good agreement with the unsteady approach in predicting aerodynamics and aeroacoustics as well as their sensitivity derivatives. Furthermore, the steady adjoint optimization demonstrates its capability in achieving an optimum rotor design that closely resembles the outcome from unsteady adjoint optimization while exhibiting a 20-fold acceleration in computational time. These results highlight the potential of this proposed pseudorotation adjoint-based optimization method in efficiently exploring fundamental principles governing high aerodynamic performance and low tonal noise emissions for isolated rotors.