An experimental investigation on the dynamics of liquid sloshing in a rectangular tank and its interaction with an internal vertical pole

Abstract

In the present study we perform shake table experiments to study the fluid structure interaction effects between the sloshing liquid and the internal structure. A partially filled storage tank is systematically subjected to (i) horizontal (ii) vertical and (iii) seismic excitations. To start with, forced horizontal excitations are imposed by varying the amplitude of excitation ranging from 0.001 L to 0.0075 L, where, L is the tank length. As the amplitude of excitation is increased, sub-harmonic wave features were observed at the wave crests, which indicate the presence of higher slosh modes. The resulting resonant free surface oscillations are validated against available theoretical and computational studies. Furthermore, the tank was subjected to vertical harmonic excitations at nth slosh frequency (ωn), where, n = 1, 2, 3 and 4 covers first four sloshing modes. The excitation frequency (Ωn = ωn∕ωv) of 0.5 and the corresponding forcing amplitudes (κv) are chosen such that, the combinations were with in the unstable range of Matheiu's instability diagram. For higher modes of vertical excitation, the free surface oscillations were found to be better damped. A detailed study of flow visuals, free surface fluctuations, dynamic pressure data, power spectral densities, structural responses etc reveal the nature of coupling with the container wall and the circular cylinder. The shake table is further programmed to simulate the well known El Centro earthquake excitation, where the storage tank is imposed with horizontal as well as combined horizontal and vertical components of excitation (at 50% of actual amplitude) to investigate the fluid structure interaction effects. When the partially filled storage tank is subjected to seismic excitation, spiky jet like features were observed over the free surface.