Effect of viscosity on sloshing in a rectangular tank with intermediate liquid depth

The viscous effects on the horizontally-excited sloshing under resonant and off-resonant excitations are investigated experimentally. Both tap water and glycerin at different temperatures are chosen as the experimental fluids. The intermediate depth ratio h/L = 0.2 is chosen. The sloshing of water and glycerin at four kinematic viscosities ranging from 1.14 x 10(-6) m(2)/s to 1.1 x 10(-3) m(2)/s is studied. Through well-controlled experiments, by analyzing the pressure and free surface snapshot, the sloshing gradually turns from the resonant-steady state to the harmonic state for a certain viscosity threshold. The free surface profiles of low and high viscous fluids under resonant excitations are further analyzed, in connection with the dynamic pressures and excitation accelerations. The peak dynamic pressures are successively out of synchrony with the peak excitation accelerations, obvious phase shift occurs which eventually goes to one fifth of the resonant frequency. Through the fast Fourier transform, it is found that the dominant response frequencies of high viscous fluids are integral times of the forcing frequency behaving a distinct state from the low viscous fluids especially for the water.