Session: 06-10-01 Offshore Industry: Structures and Design I

Paper Number: 121442

121442 - Dynamic Analysis of Offshore Triceratops With Missile Launcher 

The major and traditional function of an offshore platform is oil and gas exploration and production. The naval defense system requires strengthening on design and development of strategic platforms, which can be used for multi-utility such as rescue operations, retiring centres for maritime defense, and a floating naval base for missile launch under emergencies. It can also serve as an emergency landing platform for jets with VTOL systems. Furthermore, the increasing human threats to attack strategic platforms demand that such platforms be made self-resilient. With missile launching capability, the risk of maritime terrorism on the offshore platform will be reduced significantly. As most of the advanced offshore platforms are commissioned for unmanned operations, making them self-defensive becomes critical. The offshore triceratops is identified as a promising candidate for deployment as a maritime-based missile launcher due to its unique and innovative responsive behaviours in deep ocean environments.

The objective of the present research is to design and develop a multi-utility compliant platform that counteracts the environmental loads in addition to recoil effects caused during missile launch. The scope of work includes numerical investigations on the missile-launching triceratops under regular and irregular waves.

The offshore triceratops with a missile launcher is modelled as two rigid bodies with 9 degrees of freedom. The structure is modelled in such a way that the two rigid bodies share translational degrees of freedom while they have independent rotational degrees of freedom. This feature is ascribed to the presence of the ball joint. The platform's design follows an iterative approach, which will be repeated until the buoyancy of the structure matches the combined weight of the structure itself, the payload it carries, and the total force exerted by the tether. The meta-centric height of the resulting structure came out to be 33.4 m which confirms its hydrostatic stability. These designed parameters are used as structural and geometric inputs in the numerical analysis. Numerical analysis is carried out in ANSYS AQWA for two different conditions, namely, with and without missile launch. The structure is modelled as a surface element using the designed parameters. Free oscillation test is conducted to find out the natural time period of the structure. The time period in the heave, roll, and pitch degrees of freedom is in the range of 3 s, while that of surge, sway, and yaw is 150 s. It confirms the compliant nature of the triceratops. Whereas it is stiff in heave, pitch, and roll degrees of freedom, it is flexible in surge, sway, and yaw degrees of freedom. Furthermore, the natural time period of the structures is outside the wave time period, which ensures that resonance conditions will not take place. Subsequently, power spectral densities in the active degrees of freedom are obtained from the time response analysis.

Presenting Author: Ashish Unnikrishnan Indian Institute of Technology Madras

Presenting Author Biography: Possessing a bachelor's degree in Civil Engineering acquired from the National Institute of Technology Calicut, the individual currently assumes the role of a research scholar in the Department of Ocean Engineering, at the Indian Institute of Technology Madras. He is presently working in the area of structural dynamics applied to ocean structures. His academic pursuits are underscored by an ardent enthusiasm for the application of structural engineering to various streams of academia and industry.

Authors:

Srinivasan Chandrasekaran Indian Institute of Technology Madras
Ashish Unnikrishnan Indian Institute of Technology Madras