A fully-nonlinear potential flow model for water entry/exit in aircraft ditching applications

The aircraft ditching, despite being a rare event, has to be considered in the design phase to guarantee safety and to respect certification. As a way to avoid the expensive full scale experimental tests, computational approaches able to provide a reasonably accurate description of hydrodynamics and fluid-structure interaction taking place during the aircraft ditching are of primary interest. Besides high fidelity, fully coupled, fluid and structural solvers, fast and efficient solvers, albeit approximate, are strongly needed by aircraft manufacturers for the design and certification stage when many different configurations have to be analyzed. Simplified methods based on Modified Logvinovich Model [1] or Generalized Wagner [2] have been found to be very efficient and able to provide accurate predictions of the sectional forces. In this paper, a fully nonlinear model is developed with the aim of providing a more accurate prediction of the pressure distribution and of the fluid-structure coupling. The model is based on the mixed Eulerian-Lagrangian BEM formulation. As a preliminary step towards the development of a 2D+t procedure, in this paper the model is tested in the vertical water entry and exit of a wedge and a cone and validated against other numerical or experimental data.