CFD-Based Simulations of Hydrodynamic Behaviors of a Floating Barge Near Shore

Abstract

This paper presents Computational Fluid Dynamics (CFD)-based simulations of the hydrodynamic behaviors of a floating barge in shallow waters on an inclined seabed near shore. The hull hydrodynamic behaviors with respect to water depth are quantified by evaluation of the hydrodynamic coefficients, i.e., added mass, viscous damping coefficients, and current drag coefficients, which are required for the prediction of hull motion responses and mooring loads of the barge. CFD simulations are performed to predict the hull hydrodynamic coefficients with consideration of the actual seabed conditions, including water depth and varying bathymetry. Added mass and viscous damping coefficients are calculated using forced harmonic oscillations, while current drag coefficient is obtained using steady current flow simulation. These hydrodynamic coefficients are calculated for three of the six degrees of freedom (DOFs), i.e., surge, sway, and yaw of the hull. By considering three different nearshore water depths with a flat seabed and two inclined seabeds, the hull added mass, viscous damping, and current drag coefficients are quantified and compared against the coefficients in deepwater conditions. The hydrodynamic coefficients are found to be significantly affected by shallow water depths. Overall trends show exponential increase of added mass and viscous damping coefficients as water depth reduces. There is a further linear increase in the coefficients when the seabed bathymetry changes from flat to inclined, particularly when the water depth to hull draft ratio is less than 4.50. Similarly, current drag coefficients increase with decreasing water depths for flat seabed conditions, while for inclined seabed conditions, they may increase or decrease depending on the directions with respect to the shore and the current heading. This paper demonstrates the efficiency of CFD simulations in predicting a floating barge’s hydrodynamic behaviors in shallow water conditions, including varying nearshore bathymetry and viscous effects. The CFD simulation methodologies presented may be extended for the hydrodynamic behavior assessments of other nearshore floating structures such as Floating Offshore Liquefied Gas Terminals (FLGTs), Floating Storage and Regasification Units (FSRUs), and floating wind turbine structures.