Prediction of fluid surge in partially-filled clean-bore and transverse baffled tanks of multiple designs under the United Nations Model Regulations

Transport tanks are designed for the movement of liquids and gas by road, rail, and sea. Longitudinal fluid sloshing is a frequent occurrence, that occurs when the tank is subject to acceleration and deceleration, which influences the stability and braking performance. Installing transverse baffles in the large-compartment tank is an effective method to suppress fluid sloshing under multiple transport scenarios. In traditional CFD analysis, the maximum rigid body force (RBF) is used as the key characteristic to compare fluid damping effects among tanks with different baffle configurations. However, from an early study in Cai et al. (2021) it was shown that overprediction of the RBF occurred for a clean-bore tank when fluid hit the tank wall and separated from the main domain at high speed. The overprediction could reach up to 200% and the magnitude of overprediction was strongly dependent on the selected mesh size, time step size, flow model and occurred in the ALE/SPH/CFD solvers. The reported study simulated the fluid sloshing inside in a clean-bore, as well as six tanks with different baffle configurations. The RBF overprediction occurred for most configurations under various fluid fill ratios and longitudinal accelerations. Consequently, impulse rather than maximum RBF is recommended as the main characteristic to compare different baffle configurations. Furthermore, the simulation results indicate that in baffles with 30% of open area, as required by the United Nations Model Regulations, the change of shape of the baffle results in up to 15% change on impulse in the full tank while had up to 31% change on the maximum impulse on the baffle. Consequently, under the United Nations Model Regulations, the design engineer could put more focus to optimize the baffle shape based on the requirement to maintain the structural stability rather than the need to reduce fluid sloshing to the overall tank.