# A Study on the Movement Characteristics of Fuel in the Fuel Tank during the Maneuvering Process
###### Abstract  
To investigate the movement characteristics of fuel within an aircraft's fuel tank during maneuvering, this study employs numerical simulations using the Finite Pointset Method (FPM) with specific boundary conditions and excitation. The simulation results successfully capture the complex phenomena of fuel free surface fluctuations, surging, rolling, and breaking, along with the corresponding changes in the center of gravity induced by fuel movement. Throughout the aircraft's maneuvering process, the longitudinal center of gravity experiences minimal variations, whereas the aerodynamic center of gravity exhibits significant fluctuations, reaching a range of 0.47 m. The longitudinal center of gravity consistently shifts backward with a displacement of 0.41 m. The maximum height attained by the liquid's free surface during aircraft maneuvering measures approximately 0.22 m, reaching the upper panel's height of the wing fuel tank, resulting in a certain level of impact on the upper panel. The maximum impact force generated during the aircraft maneuvering process amounts to \(2.3\times 10^{5}\) pascals, with the point of action located at the junction of the transverse frame and the upper panel. The findings of this work provide support for the safe design of aircraft fuel tank systems. aircraft fuel system; maneuvering; free surface; wing fuel tank; Finite Pointset Method +
Footnote †: journal: Applied  
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fluid large deformation motion, combined with large eddy simulation, to calculate the dynamic response of flexible container sloshing under wind load. [PERSON] and [PERSON] [6; 7] used the VOF method to numerically simulate a three-dimensional rectangular liquid tank, calculating impulsive pressure and non-impulsive pressure. Among them, the Smoothed Particle Hydrodynamics (SPH) method is a grid-free calculation method proposed by [PERSON] [8] and [PERSON] [9] in 1977, which has been widely used in the field of fluid dynamics [10; 11]. [PERSON] and [PERSON] [12] overcame the pressure noise problem in simulating free surface hydrodynamics problems using the SPH method by the means of density filtering. [PERSON] et al. [13] theoretically proved that the weakly compressible SPH method can automatically satisfy the free surface boundary conditions at the free surface, and the truncation of the kernel function at the free surface does not affect the accuracy of the free surface simulation. [PERSON] and [PERSON] [14] numerically studied the sloshing of rectangular liquid tanks and found that, when excited near the resonance frequency, the numerical results of wave amplitude were smaller than the experimental and theoretical values. They believed that this could be due to the unreasonable reflection of liquid viscosity effects in the numerical model, but did not conduct a detailed study on this issue. Compared with traditional grid-based methods, the SPH method is suitable for simulating problems involving large deformations, free surfaces, moving boundaries, and deformable boundaries. It solves the problem of grid distortion caused by large deformations in traditional grid-based numerical methods when solving the problem of liquid shaking. However, the SPH method also has shortcomings or areas for improvement, such as poor calculation accuracy when particles are irregularly distributed, low algorithm stability, and incomplete boundary handling [15]. The literature [16] proposes using a finite number of particles to discretize the fluid domain, with each particle carrying physical information such as velocity and pressure, called the Finite Pointset Method (FPM). This method is an important development of the SPH method in the field of grid-free calculation. In terms of simulating the free surface, although there are relevant literature and demonstrations in different technical fields, most of them are based on traditional Smoothed Particle Hydrodynamics (SPH), Arbitrary Lagrangian-Eulerian (ALE) and dynamic mesh methods.