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A directional dynamic model of a partially filled liquid tank vehicle is developed to investigate its dynamic characteristics during typical straight-line braking maneuvers. The computer simulation model is developed by integrating the fluid slosh model of a partially filled tank to the pitch plane vehicle model. The dynamic behavior of liquid within the tank is modeled using an equivalent mass-spring system. The analogous mechanical system model for the partially filled cleanbore cylindrical tank is developed by utilizing the potential flow theory for longitudinal oscillations. An approximate summation method is developed in order to obtain the mechanical system parameters and are validated against experimental results available in literature. Computer simulation of the tank vehicle for typical braking maneuvers is then performed by incorporating the slosh forces and moments computed using the mechanical analogy model into the vehicle model.

The computation of dynamic slosh forces arising due to liquid motion within a partially filled tank is quite important in analyzing the directional behavior of tank trucks during various highway maneuvers. The most precise computation of liquid motion and the associated slosh forces involves solving complex non-linear fluid mechanics equations and is extremely cumbersome. The motion of liquid within a partially filled tank is herein investigated by representing the fluid slosh through an equivalent mechanical system using a pendulum analogy model. The model parameters are computed based on inviscid fluid flow conditions and the dynamic fluid slosh forces arising due to the dynamics of the vehicle during a given maneuver are computed using the equivalent mechanical system. The dynamic fluid slosh forces and moments are then integrated into the vehicle dynamics model to study the directional response characteristics of tank vehicles.