Abstract

As a high-performance ship, trimaran is composed of a main hull and two slender side hulls. It has obvious advantages over monohull and catamaran in rapidity, seakeeping, stealth and general arrangement. Taking a trimaran as the research object, this paper uses the Multidisciplinary optimization platform for ship hydrodynamic performance (SHIPMDO-WUT) independently developed by our research team to carry out optimization. This platform uses Radial Basis Function interpolation method (RBF) to modify the ship hull form. The objective function of the optimization is wave-making resistance coefficient (Cw). In order to explore the influence of hull form and sidehull arrangements on the Cw of trimaran, the optimization is divided into two steps: The first step is only to optimize the side-hull arrangements. The second step is to optimize the hull form and side-hull arrangements comprehensively. The optimization results show that 1) arrangements modifying is significantly affected Cw of trimaran. 2) modifying the hull form will change the best position of side hulls and there is a relationship between arrangements and hull form.

INTRODUCTION

With the proposal and implementation of energy efficiency design index (EEDI) by IMO, energy conservation and emission reduction has become an important index in ship design. Trimaran, as a kind of highperformance ship, has been widely concerned since it came into being. It has broad application prospects in both civil and military fields for its excellent rapidity and Seakeeping performance. Compared with conventional monohull, trimaran has two side hulls, larger deck area and flexible general layout. In the aspect of resistance performance, two side hulls can form favorable interference with the main hull, so as to effectively reduce wave making resistance.

In recent years, in the field of hull form optimization, many scholars have studied the resistance performance optimization of trimaran. Daniel Floden (2004) used Shipflow to optimize the position of side hulls under various speeds, and analyzed the influence of side body position on wave making resistance. Palmers (2015) changed the position of the side hull and used an improved Particle Swarm Optimization algorithm to find the position of the side body with the minimum resistance. Mizine et al. (2008) used Shipflow to predict the wave making resistance of trimaran. The result verified the calculation accuracy of Shipflow, and obtained the influence of the main hull and side hull on the wave making resistance. Mahmood S. et al. (2011) Optimized the trimaran form by only considering the main hull and keeping the side hull unchanged. Yang Chi et al. (2015) considered both the position of side hulls and the hull form of side body. First, CFD calculation was carried out for nine different positions of side hulls to obtain the optimal position of resistance. Then the hull form of side hull was optimized to obtain the optimal profile of side hull at three design speeds (Fn = 0.25, 0.35 and 0.45). Liu Xinwang (2019) optimized the side hull position of trimaran by using the self-developed ship form optimization software, which reduced the total resistance by 44%. Sun Lina (2015) adopted the idea of hierarchical optimization, firstly optimized the position of side, and then completed the optimization of hull form under various speeds based on the optimal position. Zong Zhi (2018) used six parameters to optimize coefficient of total resistance (CT) of a trimaran, three to control the hull form of the main hull, two to change the position of side hulls and the rest one being length ratio of new side hull to original side hull. CT of the optimized trimaran decreased by 21.34%.

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