Straight-line braking dynamic analysis of a partly filled baffled and unbaffled tank truck

Abstract

The straight-line braking performance characteristics of a partly filled tank truck with and without transverse baffles are investigated in the presence of transient fluid slosh within the tank. The dynamic interactions of the floating cargo with the vehicle are evaluated by integrating a dynamic fluid slosh model of the partly filled tank with and without transverse baffles with the seven-degrees-of-freedom pitch plane model of a tridem truck. The dynamic fluid slosh within the tank containing equally spaced four curved single-orifice baffles with flow equalizer is modelled using three-dimensional Navier—Stokes equations coupled with the volume-of-fluid equation and analysed using the FLUENT software. The coupled tank—vehicle model is subsequently analysed to determine the straight-line braking properties for different fill volumes, magnitudes of braking treadle pressure, and road surface adhesion coefficients, while the cargo load is considered to be constant. The results show interactions of the sloshing cargo with the vehicle. A degradation of the braking performance of the partly filled tank truck is evident in the presence of transient fluid slosh, particularly in the absence of baffles. The braking performance, however, is highly dependent upon the fill volume, presence of baffles, and severity of braking input. For a clean-bore tank truck, the stopping distance increases monotonically with decreasing fill volume, while the addition of transverse baffles in general results in considerably shorter stopping distance. The baffled tank truck, however, reveals a relatively shorter stopping distance under an intermediate fill condition (approximately 52.1 per cent), compared with the lower and higher fill volumes. Although the analyses are limited to conventional single-orifice baffles, the proposed coupled vehicle—tank model could serve as an important tool for exploring alternative baffle designs and layouts.