Development of Effective Baffle Configuration for Slosh Response Control In Liquid Storage Tanks

Abstract

The quantification and damping of slosh responses have become important due to the increasing demand for the safety of the liquid tanks under severe external excitations. There is uncertainties in the selection of an effective configuration of the baffle plate as an anti-slosh mechanism. Therefore, the present study focuses on the development of an effective configuration of perforated baffle plate by analysing the slosh responses of the liquid tanks under seismic ground motions and pitch excitations. Initially, modal analysis was carried out to investigate the dynamic characteristics of cylindrical as well as rectangular liquid tanks. Subsequently, nonlinear dynamic analysis under seismic ground motions of different PGA/PGV ratios has been carried out, considering the models of rectangular tanks with and without baffle plates. A detailed parametric study is carried out by considering the effects of the percentage of perforation, inter perforation distance, size of perforations, offset distance of the perforated plate, the distance between the perforated baffle plates, alignment of perforations, and the vertical position of perforated baffle plate on the slosh damping efficiency of liquid tanks. The slosh responses are observed in terms of free surface elevation and hydrodynamic pressure as major response parameters. The parametric study is extended for the response of a small-scale model under pitch excitation as well. Finally, the experimental validation of the developed configuration of the baffle plate is done on the same small-scale model using a shake table test. Modification coefficients for the standard codal expressions are suggested for the accurate estimation of the fundamental impulsive frequency of cylindrical tanks. The frequency values decrease with the installation of baffle plates in the rectangular tanks. The optimum perforation of the baffle plate is in the range of 5% to 17%, considering the responses under convective as well as impulsive conditions that should be selected based on the frequency characteristics of the sloshing liquid and the input motion along with the requirements for weight reduction. The study identified different zones and damping ranges to pilot the positioning of the perforated baffle plate in the liquid tanks. Additionally, a novel ‘zig-zag blocking alignment’ of perforations for the perforated baffle plates to damp the slosh response under both convective and impulsive modes of response, which can be applied even under severe sloshing conditions, has been developed.