In recent years, an airplane is widely applied to the coastal fields, leading to the gradual increase of the occurrence of airplane's emergency landing on water surface. In such case, the study on the ditching is now considered as one key part of safety performances of an airplane. Theoretically, the relevant study on water ditching is essentially one problem involving a water entry, which is very difficult due to strongly nonlinear feature, e.g. a free-surface. In this paper, an in-house developed nonlinear LES (large eddy simulation) two-phase Navier-Stokes solver is used for simulating the problem during the water entry of an airplane, over a fixed Cartesian grid. The free-surface is captured with the VOF approach. The calculated results with the parameters variation of the ditching like the attack angle and the speed of the entry are represented.
Water ditching is an emergency when an aircraft is unable to continue its flight in case of an accident. As early as the late 1950s, the United States took the lead in launching a study on the technology of airplane's emergency landing on water surface. Then, A lot of experiments and theoretical analyzes have been done. Recently, various numerical methods on the aircraft design and verification process are being emphasized. Compared with the costly and time-consuming model experiment, the numerical simulation method is characteristic of low-cost, flexibility and convenience.
Essentially, airplane's emergency landing on water surface belongs to the water impact problem, which is generally a two-phase flow (water and air) problem involving a moving solid boundary. Recently, various theoretic models on the study of the water impact are applied and there has been significant progress in this area, for example, by using a SPH (smoothed particle hydrodynamics) method for fluid-structure interaction (Campbell and Vignjevic, 2012). Within the framework of the grid-based technique, the communication between an immersed moving boundary and its surrounding flows remains an issue for moving boundary problems, as addressed probably in several ways, by adding a positive (or negative) source term in the pressure Poisson solver (Liu et al., 2005) and by introducing the grid velocity into the advective term (Wang and Wang, 2014), based on the cut-cell approach of Causon et al., (2001). The relevant study can be found in Cheny and Botella (2010) for the immersed moving boundary by interpolation.
