Experimental study on nonlinear sloshing frequency in shallow water tanks under the effects of excitation amplitude and dispersion parameter

Abstract

Sloshing of liquid in partially filled tanks under high excitation amplitude is always a complicated phenomenon for shallow water condition. This complication arises due to nonlinear behaviour of liquid free-surface motion when the excitation amplitude is sufficiently large. Due to nonlinearity, the sloshing resonant frequency also gets affected and so the performance of several devices developed based on linear sloshing concept is disturbed. One widely studied and used such device is Tuned Liquid Damper (TLD). In the present study, a series of experiments has been conducted to investigate the nonlinear shallow water sloshing in detail. Experimental tests were carried out for tanks of different base-aspect ratios (length to width of tank), different water-depths, wide range of excitation amplitudes and frequencies. Nonlinear characteristics such as frequency jump-phenomenon, shift in resonant frequency, super-harmonic resonance, responses at higher harmonics and fractional harmonics of forcing frequency have been reported. It has been found that the resonant frequency is sensitive to the excitation amplitude and dispersion parameter (ratio of water-depth to tank-length). For a tank of large aspect-ratio under high excitation amplitude, it is also found that the resonance frequency increases about 45% in comparison to the linear sloshing frequency.