Modeling and Simulation of Vehicles Carrying Liquid Cargo

A method for modeling and simulation of the dynamics ofvehicles subject to liquid slosh loads is presented. The vehiclecomponents are modeled as a multibody system, the sloshing liquiddynamics is determined from solving the instationary, incompressibleNavier–Stokes equations under consideration of free surfaces. Toanalyze the overall system dynamics, the concept of modular simulationis applied decomposing the dynamic system into subsystems. The rigidbody and fluid subsystems are modeled by separate software codes whichare coupled by the transfer of in- and output variables duringsimulation runtime.To account for the vehicle motions, thefluid equations of motion are transformed into a moving frame ofreference, inputs and outputs of the fluid subsystem are derived. Forsolving the incompressible Navier–Stokes equations, efficient methodshave to be applied. The system of equations resulting from a FiniteVolume discretization is solved by a multigrid method, the location offree surfaces is determined by a Volume-of-Fluid approach. To validatethe methods for modeling fluid dynamics, benchmark calculations of theflow around a cylinder and the collapse of a water column are presented.The proposed method for modeling the interaction of sloshingliquids and vehicle motions is used to determine the brakingcharacteristics of partially liquid-filled tank vehicles. It is shownthat a loss of directional control due to wheel lock-up is more likelyfor tank vehicles with sloshing liquid cargo than for vehicles loadedwith equivalent rigid cargo because of the dynamic liquid load shift.