EFFECT OF FREE SURFACE WAVE ON FREE VIBRATION OF A FLOATING PLATFORM

Bhagirathi Tripathy, Pratap Kumar Pani

Abstract: Use of floating structures is very common and widespread. Starting from boats, ships and submarines they are used these days for various purposes like platforms for industrial use like offshore oil exploration, civic amenities like floating air strips, defense bases and in some island nations for recreation and habitation. Hence, strength and stability of these platforms are very important. In the present study, the fluid-structure interaction effect on the free vibration frequency of a floating platform is investigated. The fluid is treated as inviscid, incompressible and having a small amplitude irrotational motion. The platform is considered to be of rectangular in size and is made of homogeneous material following Hooke’s law. Finite element technique is adopted for the solution of this problem with eight noded brick elements for the fluid and four noded quadrilateral elements for the plate. The interaction problem of the platform and the fluid is solved independently for the platform and the fluid domain by transferring the pressure to the platform from the fluid and the acceleration of the platform to the fluid sequentially. The effects of the surface wave, thickness and aspect ratio of the platform on free vibration frequencies are studied. It is observed that surface wave reduces the free vibration frequencies significantly for frequencies those are due to the bulging modes of the platform.

Keywords: Inviscid, Irrotational, Hydro elasticity, Eigen frequencies, Eigen value

DOI: https://doi.org/10.15623/ijret.2013.0209010