Smoothed Particle Hydrodynamics For Aircraft Ditching

Aircraft ditching performance as an important index to measure the safety,its essence is such a complex problem of nonlinear large deformation of fluid-solid coupling. Therefore, the effective tool of numerical simulation is of great significance. In this paper, in order to simulate the water entry problems of unsteady, nonlinear, and the accompanying phenomenon of spitting, developed a based on smooth particle hydrodynamics(SPH) numerical simulation software, was applied to study included helicopter and civil aircraft ditching problems, has important value of engineering application.This article first embarking from the integral interpolation introduces the basic principle of SPH method, and deduces the SPH form of basic equations of hydrodynamics; use a method which virtual particles fill the truncation domain of support filed by boundary to process the fluid particles near the wall, which can effectively simulate complex boundary shape. Meanwhile the quaternion method is used to describe the body kinematics equation, to avoid the singularity problem when solving rigid body motion with general method.In the process of program design, according to the requirements analysis, the software includes data input, particle generation, SPH solver, the motion law of solution, calculating process monitoring and result output and UI six function modules. At the same time, it is developing a combination of Verlet-list and Cell-list neighboring particles searching algorithm and reordering the particles with Morton Key/Z-curve order method, greatly improving the efficiency of the software. In addition, in order to improve the stability of the software, tensile instability correction, modification of kernel function and the reconstruction of density are used, and the effect is remarkable. Thus, paper use two-dimensional dam break, two-dimensional wedge water entry, there-dimensional dam break and the water landing problem of capsule for example to verify the accuracy and robustness of the algorithm and software and the ability to solve complex problems.At the last of the paper, the numerical simulation software is used to study the helicopter and civil aircraft ditching problems of complex geometrical shape. A helicopter model with varies pitching angle of 6, 8, and 10 degree was simulated, which obtaining the good water splash effect and accurate overload. And simulating the DLR-F12 aircraft model using the real condition of slip angle, satisfactory results were obtained.