Investigation and Development of Fuel Slosh CAE Methodologies 2014-01-1632
When a vehicle with a partially filled fuel tank undergoes sudden acceleration, braking, turning or pitching motion, fuel sloshing is experienced. It is important to establish a CAE methodology to accurately predict slosh phenomenon. Fuel slosh can lead to many failure modes such as noise, erroneous fuel indication, irregular fuel supply at low fuel level and durability issues caused by high impact forces on tank surface and internal parts. This paper summarizes activities carried out by the fuel system team at Ford Motor Company to develop and validate such CAE methodology. In particular two methods are discussed here. The first method is Volume Of Fluid (VOF) based incompressible multiphase Eulerian transient CAE method. The CFD solvers used here are Star CD and Star CCM+. The second method incorporates Fluid-Structure interaction (FSI) using Arbitrary Lagrangian-Eulerian (ALE) formulation. While Eulerian domain predicts motion and forces of fluid inside the tank, Lagrangian domain models tank shell and predicts its vibration under these forces. Solver used here is LS-DYNA. While details of second method are covered in another publication  by co-author of this paper, Dr. Usman, first method is focused on in greater detail due to its successful integration in to design verification (DV) process. Many engineering quantities such as tank surface pressure vs. time plot, surface integral force, momentum, mean kinetic energy, free surface shape etc. are monitored. However, surface pressure time history, surface integral force and free surface shape are found to be the most useful information to characterize slosh behavior and correlate with the test. Simulation results are compared with bench test. Issues related to effect of pressure reference location, wall Y+, courant number, mesh size and inner iteration are also discussed. Current CFD method is fully developed and integrated in the product design process to evaluate tank and baffle design early in the process to avoid costly tool changes or extensive testing. This method can be combined with other analytical tools to further include effect of aero/fluid acoustic and vehicle architecture.