Objectives This study seeks to design an original bilge keel for a 66 m ocean-going squid fishing boat and optimize the design scheme to improve its wave resistance and ensure the boat's rapidity.

Methods By converting the length and width of a bilge keel, five more bilge keels of different sizes are designed. Based on the computational fluid dynamics (CFD) method, the volume of fluid (VOF) model and overlap grid technology are used to numerically simulate the free roll attenuation of these six different bilge keels and obtain reliable resistance values and free roll attenuation time curves. The effects of bilge keel length, width and length-to-width ratio on the roll motion are studied. Through a comparison of roll motion, three optimization schemes with better roll reduction effects are selected, and the numerical simulation of resistance is carried out to study the optimization design schemes.

Results As the simulation results show, compared with Model 0, the roll damping of Model 3 increases by 23.37% when Fr = 0, increases by 25.31% when Fr = 0.168 and increases by 85.80% when Fr = 0.230, providing a superior roll damping effect. Moreover, among the three bilge keels with good roll damping effects, compared with Model 0, Model 3 has the smallest resistance increase value, which can meet the requirements for the boat's rapidity on the basis of obtaining good wave resistance.

Conclusions The results of this study can provide useful references for improving the wave resistance and selection of bilge keels for ocean-going squid fishing boats.