Systematic Study of Green water and its Impact on Structures

The Offshore Industry is one of the most challenging industries. Offshore vessels must survive all weather conditions over its lifetime. In heavy storms, waves and ship motions become so large that water flows onto the deck, It is referred to as Green Water and is a serious challenge that needs to be considered in designing offshore vessels. The methods for making green water prediction are limited. More data needs to be collected to ensure safe navigation and operation. ComFLOW is a numerical tool in the field of Offshore Engineering used to study these non- linear and complex green water phenomena. ComFLOW is a Navier-Stokes solver with Volume of Fluid(VOF) for free surface motion, It has been used for simulation of dam break flows as a model for green water flow on deck and falling objects in calm waters. In this research, it is used to generate dam-break waves along with simulations involving regular and irregular waves leading to water on deck. It is used to evaluate whether dam break model is a complete model for studying green water loading on deck. A grid convergence study for ComFLOW is conducted along with a verification of ComFLOW for 2 dimensions. Optimum grid cell size is advised for accurate and stable results in ComFLOW for 2 dimensions. Dam break simulations are performed on an idealized deck to observe changes from that of a regular domain boundary. Wave prediction and it’s impact on the topside facilities due to regular and irregular waves is the objective of this research. Absorbing boundary conditions are used to prevent wave reflections. Non-breaking waves are generated for irregular waves. Impact of water on the structure on deck is of primary importance. The wave height is an important parameter in dealing with such green water events. The role of wave height along with the distance of structure on deck is studied in this research. The input parameters such as dam height and distance of the structure from dam height are varied. Localized impact pressures are considered and changes in impact pressure are observed. A structure in regular and irregular waves is also compared with a dam break model. The main conclusions are: • Variations in dam break loads compare well to theory. • The dam break is not a complete model for assessing green water loads.