Free vibration analysis of rectangular water tank considering baffle-fluid interaction

Abstract

In the present study, the convective time period of rectangular tanks with elastic baffle within it, is investigated by pressure based finite element method. The fluid within the tank is considered to be water and tank walls are assumed as rigid. The fluid with in the tank is considered as inviscid and fluid motion is irrotational. Galerkin approach is used for finite element formulation of wave equation fluid within tanks. However, displacement based finite element is used to simulate the elastic baffle. A direct coupling approach is used to incorporate the baffle-fluid interaction. The present algorithm also includes the compressibility of water in the reservoir. The efficacy of the present algorithm has been demonstrated through numerous examples. The convective time period increases with the addition of elastic baffle within the tanks. The convective time period increases with the increase of length of tank. The height of fluid also increases this time period. However, the influence of change of height of fluid is greater than those for the change of length. The third convective time period of tank with and without baffle are equal for comparatively lower length but for first convective time period this occurs for comparatively large length. The free vibration responses also increase with the increase of flexibility of baffle wall because the convective time period increases with the increase of baffle height. Position of the baffle also influences the free vibration response of the tank with baffle. The first two convective time periods have the highest value when it is near to the tank wall and the lowest value when it is placed near the midpoint of tank. But for third convective time period has the highest value when it is placed at the middle and gains the least value at one-fourth distance from tank wall. Similar to the height of baffle, the thickness of baffle also changes the flexibility of baffle hence the increase of thickness of baffle reduces the convective time period of the tank.