Numerical Study Of Nonlinear Liquid Sloshing And Its Applications On Tank Truck

Liquid sloshing and the interaction of liquid-structure widely exist in many engineering fields. It is difficult to calculate large amplitude sloshing, because it usually has strong nonlinear property. Specially, system stability of tank would be influenced severely by impact load imposed by violent liquid sloshing, leading to damage of the structure. So it is important, both in theory and practical purpose, to study the characteristics of liquid sloshing dynamics. For a tank truck, sloshing caused by its movement would also affect the stability and ride comfort of the vehicle. In this paper, nonlinear liquid sloshing and vibration of liquid-structure coupling system are studied by numerical methods; and the liquid sloshing effect in a moving tank truck is also discussed.Firstly, a modified numerical method for two dimensional nonlinear sloshing problems is proposed, σ-transformation is used to change the fluid domain into a fixed rectangular area. The free surface of next time step is predicted and then substituted into the continuity equation and rigid wall boundary conditions. An approximate technique is introduced in boundary conditions of free surface and the equations are linearized. The solution of the equations will be taken as the correct value of free surface on the next time step. This method has good convergence and numerical stability, and is suitable for solving mathematical problems with moving boundaries.Secondly, the numerical examples of standing waves, forced sloshing in horizontally and vertically excited tanks are calculated. In order to verify the accuracy of the method, the numerical results are compared with analytical solutions. Nonlinear characteristics of large amplitude sloshing are revealed by the results; while the effect of some factors such as frequency, amplitude of excitation and initial free surface on sloshing nonlinearity is also investigated. Moreover, forced sloshing under horizontal excitation is experimentally studied.Thirdly, horizontal and vertical vibration models of liquid-structure coupling systems are presented. A numerical method based on the preceding computational scheme for nonlinear sloshing is proposed to solve coupled dynamical equations. For the horizontal vibration of coupling system, sloshing nonlinearity is studied in free oscillations and resonant situations of all orders. For the vertical vibration of coupling system, stability of sloshing during the process of vibration is discussed, while the influence of nonlinear factors on the movement of the tank is also investigated.Finally, taking tank truck as the research object, the effect of liquid sloshing on brake performance and ride comfort is studied. The motion of free surface and sloshing force acting on the tank in brake process is simulated by numerical method. The changes of sloshing force and nonlinear effect are discussed under different conditions of acceleration and filling rate. The vibration model of 1/4 tank truck is established; and the dynamic response of this model is calculated under random road excitation. The results show that the power spectral density of tank acceleration can be decomposed into linear and nonlinear frequency parts. In addition, the effect of sloshing suppression with baffle and the optimization of vehicle ride comfort are also analyzed.