Research on vibration characteristics of multi-tiered tank structure with a horizontal plate with openings

Abstract

In this study, vibration characteristics of a rectangular tank with a horizontal plate to divide inside liquid are examined by model test and FE analysis. The plate in the tank has an opening at the center, which allows fluid in the tank to pass through it up and down.Vibration tests are performed with the change of water level and opening size and acceleration responses of the tank walls are measured. The effect of opening size, position of openings and number of openings are also examined using FE analysis. Main conclusions are as follows.(1) With the increase of water level, natural frequency of the tank drastically drops when water level passes up the divider plate,especially when the area of hole on the plate is small.(2) Damping ratio of 1st mode increases as the ratio of the area of hole of a divider plate decreases.(3) Natural frequency of a tank is dependent on the size, position and number of openings. The size of an opening has most significant effect on natural frequency.(4) Tank design method to avoid resonance can be newly developed making use of the vibration characteristics shown above.