Free vibration analysis of stiffened lock gate structure coupled with fluid

Abstract

Free vibration analysis of rectangular stiffened lock gate structure is investigated to analyse the effect of fluid on the gate structure. Mindlin’s plate and Euler’s beam theories are used to formulate the isotropic plate and the stiffener, respectively. The fluid is assumed to be incompressible and inviscid resulting in an irrotational flow field. The far boundary of the fluid domain is truncated near the lock gate structure. The truncation of far boundary of the fluid domain is made by considering the Fourier half range cosine series expansion of Laplace equation. The theoretical formulation of the coupled problem of fluid-structure interaction is derived and it is transformed into a computer program. Similar study has been found in open literature for the lower order elements with unstiffened plate. In the present study, nine noded isoparametric plate element, three noded isoparametric beam element and twenty-seven noded isoparametric brick element have been used to discretise the plate, stiffener and fluid domain, respectively. The results obtained are compared with the reported one, which indicates the acceptance of the developed computer codes. The natural frequencies of stiffened lock gate coupled with and without fluid are evaluated by varying the dimensions of lock gate, stiffener and fluid domain.