PARAMETRIC INSTABILITY OF THE PLANE FREE SURFACE OF THE LIQUID IN CYLINDRICAL STORAGE TANKS

The paper deals with the dynamic analysis of the ground-supported cylindrical vertical liquid storage tanks with the aim to determine the response of the upper liquid portion during vertical excitation. Tanks are used as storage for liquids in various sectors of industry. Hence, it is a request for satisfactory performance during dynamic loadings (e.g. earthquakes). The paper is dedicated to the phenomenon associated with the vertical oscillations of the liquid which results in the standing waves at the free surface known as Faraday waves. The analysis of a linear mathematical model for ideal liquid subjected to the vertical excitation with the constant amplitude and frequency is presented. It takes into account the theory introduced by Benjamin and Ursell which leads to the Mathieu equation for parametric vibration. Using Mathieu formulation, the mth mode of oscillation is excited when the combination of parameters corresponding to the amplitude and frequency lies in an unstable region of the stability chart. The free surface remains plane when assuming a pair of parameters in a stable region.