Frequencies of Lock Gate Structure Coupled with Reservoir Fluid

This study determines the natural frequencies of the lock gate structure, considering the coupled effect of reservoir fluid on one side using the finite element method (FEM). The gate is assumed to be a uniformly thick plate, and its material is isotropic, homogeneous, and elastic. The reservoir fluid is assumed to be inviscid and incompressible in an irrotational flow field. The length of the reservoir domain is truncated using the far boundary condition by adopting the Fourier series expansion theory. Two different assumptions on the free surface, i.e., undisturbed and linearized, are considered in the fluid domain analysis. The computer code is written based on the developed finite element formulations. The natural frequencies of the lock gate are computed when interacting with and without reservoir fluid. Several numerical problems are studied considering the effects of boundary conditions, aspect ratios, and varying dimensions of the gate and the fluid domain. The frequencies of gate reduce significantly due to the presence of fluid. The frequencies increase when the fluid extends to either side of the gate. The frequencies reduce when the depth of the fluid domain above the top edge of the gate increases. The frequencies drop considerably when the free surface condition is taken into account. The results of frequencies of lock gate structure may be useful to the designer if it is experienced in natural catastrophes.