Session: 08-01-02 Hydrodynamic Interaction and Unsteady Effects

Submission Number: 156334

A Study on the Hydrodynamic Interactions Between Demi-Hulls on Roll Damping of a Catamaran Type Crew Transfer Vessel Using RANS Simulations 

The utilization of Crew Transfer Vessels (CTVs) has been increasing in recent years, particularly for maintenance of offshore wind power facilities. Among various types, catamaran-type CTVs have gained attention due to their superior speed, stability, and expansive deck area. However, despite their high stability, catamaran-type CTVs exhibit shorter natural roll periods compared to monohull vessels, which can lead to reduced ride comfort. Consequently, understanding and mitigating roll motion through the elucidation of roll damping mechanisms is an important research topic. While studies on the roll damping of monohull vessels are abundant, research focusing on catamarans is relatively scarce. Notably, Katayama et al. (2008) conducted a representative study, but detailed investigations into the mechanisms of roll damping and the hydrodynamic interference effects between demi-hulls remain limited.

This study aims to clarify the mechanisms of roll damping forces in a general catamaran-type CTV using Reynolds-Averaged Navier-Stokes (RANS) simulations. We conducted forced roll simulations to estimate the added moment of inertia and damping coefficients associated with roll motion. These computational results were validated by comparing them with existing data from similar hull types, confirming their reliability. To further understand the contributions to roll damping, towing simulations at a fixed heel angle were performed to isolate the lift components. Additionally, we carried out forced roll simulations on a single demi-hull to investigate the flow characteristics without hydrodynamic interference from the other demi-hull.

By comparing the results from the single demi-hull simulations with those of the full catamaran configuration, we identified hydrodynamic interference effects between the demi-hulls. Differences in vorticity, velocity fields, wave height distributions around the hulls, and pressure distributions on the hull surfaces were analyzed. These differences contribute to the overall roll damping behavior of the vessel. The lift components obtained from the fixed heel angle towing simulations provided further insights into the role of lift forces in the roll damping mechanism.

Our findings reveal that the hydrodynamic interference between demi-hulls influences the roll damping characteristics of a catamaran-type CTV. The interference alters the flow patterns and pressure fields around the hulls, which in turn affect the damping forces experienced during roll motion. This highlights the importance of considering these interference effects in the design and analysis of catamaran vessels.

Presenting Author: Motoki Araki National Maritime Research Institute, Japan

Presenting Author Biography: Received the Ph.D degree of Engineering from Osaka University, Japan in 2013. Joined to CFD research group of National Maritime Research Institute (NMRI) in 2013 and move to deep sea technology research group of NMRI in 2016. Currently works on riser system of deep sea mining and application of CFD on ocean engineering field.