A Method for Optimizing the Hull Form of Fishing Vessels

Abstract

Hull optimization is an important aspect of ship design to improve safety and economic-technical efficiency for ships. This problem has been studied for a long time and has achieved many significant results, but in practical applications, there are still some contents that need to be improved such as the presentation and transformation of the existing hulls, an optimal mathematical model suitable for a specific type of ship, or method for solving the objective function, etc. On that basis, in this paper, a method for optimizing the hull form of fishing vessels is presented, including algorithms using interpolating cubic spline to generate the existing hulls that pass exactly through the given offsets and are constructed in a format to use both Computational Fluid Dynamics (CFD) analysis in resistance prediction and Lackenby method in hull form transformation, a suitable mathematical model for hull optimization problem of fishing vessels, an effective solver based on a combination of CFD, Kriging surrogate models, and traditional optimization techniques. In addition, solutions for improving the accuracy of CFD-based resistance predictions are also presented based on ensuring the accuracy of the 3D hull models and determining the suitable input parameters used for CFD simulations. This study was applied to optimize the hull form of a Vietnamese traditional wooden fishing vessel, symbol MH076, and obtained results that are consistent with the theoretical and practical trends, with the deviations of CFD-based resistance values and corresponding model test data are within the range of 63% and the reduction in total resistance or required power at design operating is around 8.81%.

Comparative Analysis of Slamming Phenomenon Prediction between U and V Hulls using Strip Theory Method

“…The value in the table is calculated using Equation ( 19), while the value is calculated using Equation (20). The difference in the slamming probability value (D%) is calculated using Equation (21).…”

“…With this slight difference value, the two hulls can be considered to have the same value for some parameters, so that the comparative resistance value can be analyzed properly. (21) The values that are strikingly different from the two hulls are the values of wetted surface area ( ),…”

“…The results of the calculations are presented in Table 2. As a comparative analysis tool, Equation (21) was used here and also for the next comparations.…”

“…The ship's hull is never separated from the problem of the ship's motion in the wavy sea so the hull form design must be able to overcome it [16], One of the dynamic effects of the ship's motion in the wavy sea is the slamming phenomenon [17], Slamming is an event where the hull of the ship experiences a phase difference with the phase of the ocean waves, which causes the bottom of the bow to be lifted from the surface and down to hit the waves [18], Some literature describes the shape of the hull on the seakeeping performance of the ship, one of which is the modified hull shape which is optimized by linear regression [19] and a inverse design method [20], The optimization of the shape of the hull with the transformation method [21] to improve the seakeeping of fishing boats was conducted [22], The optimization with shape transformation on fast boats has also been carried out [23], The shape of the hull that resembles the letters U and V has a difference in the WPA (Water Plan Area) value where the WPA will greatly affect seakeeping performance, including slamming events [24],…”