Twin Hull Vessels Research Articles

A Novel BEM for the Hydrodynamic Analysis of Twin-Hull Vessels with Application to Solar Ships

A novel Boundary Element Method (BEM) is presented for predicting the hydrodynamic behavior of twin-hull vessels, traveling at low speeds, aiming to quantify the benefits of integrating solar technology onboard. In particular, the power requirements of an electric 33 m long twin-hull ship are examined. The study discusses the placement of solar panels on deck and assesses their utilization in terms of real-time energy generation, aiming to extend the autonomy range while also reducing carbon emissions. The discussed methodology predicts the power needs by considering various operational variables, design specifications and hydrodynamic principles. In addition, it addresses the viability and possible advantages of integrating solar technology onboard and provides preliminary estimates regarding the extent to which solar energy may compensate for power needs, based on several factors, including the velocity, the prevailing sea state and the incident solar irradiance. The results provide useful information regarding the utilization of solar energy in the shipping sector, in addition to advancing sustainable maritime propulsion.

Three-dimensional Effects on Gap-Resonances in Twin-Hull Vessels in Time-Harmonic Vertical Oscillations

Three-dimensional effects induced by dimensional ratios on the gap resonances happening in twin hull vessels oscillating in forced vertical motion have been analyzed. They can lead to relevant consequences, such as the amplification of the inner radiated waves or the generation of standing waves in between the demi-hulls, that can have a direct effect on the operating profile of the vessel. The response of twin hull vessels in waves can be strongly affected by these resonant phenomena. Also, some of these behaviors can be exploited in the framework of wave energy conversion systems. The present analysis is carried out by using an open-source, linear, Boundary Element Method (BEM), based on the Green function approach. Mathematical backgrounds of the added mass and damping coefficients computation for a floating body under harmonic vertical oscillation are provided as well as details of the numerical discretization used in the BEM. A panel mesh sensitivity study is carried out and the numerical prediction is validated by comparison against available experimental data, another CFD solution obtained by a high-fidelity viscous solver based on the open-source libraries Open-FOAM and approximate analytic formulations. The effect of the beam ratio and the length-to-beam ratio on the resonant phenomena has been analyzed. This has been achieved by systematic variations of the geometric dimensions of the hull, focusing on the trends of the hydrodynamic coefficients, the amplitude of the radiated waves, and the location of the resonant frequencies over the analyzed range.

Numerical analysis of the offshore wind turbine pre-mating process using a low-height lifting system for a nonconventional installation vessel

The offshore wind industry is a growing business. New and alternative installation methods which have the potential to reduce the cost of developing offshore wind farms are urgently needed. In this paper, an innovative concept that is tentatively designed for median or large water-depth sites is studied. The conventional jacked-up installation vessel is replaced by the small waterplane area twin-hull vessel (SWATH) equipped with the dynamic position (DP) system, and the heavy lifting is replaced by the low-height lifting crane with lifting wires for lowering the assembled OWT to the floating foundation. The global dynamic responses of the installation system under environmental loads are investigated by the fully coupled nonlinear numerical models, and the corresponding strength capacity for the lifting crane is validated. Several sea states are selected to study the feasibility of the concept, and the response variables of the OWT tower mating point (i.e., the displacement and velocity) are analyzed under different loading conditions. The lifting wires and selected lifting crane components are also investigated to understand their force situations. Some interesting conclusions are drawn, which can provide references for introducing the control system to the low-height lifting system and further optimizing the concept.

Dynamic response of a SWATH vessel for installing pre-assembled floating wind turbines

New and efficient installation concepts which can reduce the cost of developing an offshore wind farm are of particular interest. This paper explores a promising concept using the small water-plane area twin-hull vessel (SWATH) to install pre-assembled wind turbines (OWT) onto floating spar foundations. A focus is placed on the hydrodynamic performance of the SWATH and the response analysis of the coupled SWATH-spar system. Firstly, the numerically calculated difference-frequency wave force effect and damping forces of the original SWATH were verified with experimental data. Secondly, the original SWATH was modified to satisfy the criteria of weight-carrying capacity and hydrostatic stability. Thirdly, a multibody numerical model for the SWATH-spar system was developed, in which the hydrodynamic and mechanical couplings between the SWATH and a spar were considered. The SWATH is equipped with a dynamic positioning system to counteract the slow-drift wave force effects. The nonlinear time-domain simulations were carried out for the mating stage when a wind turbine is lifted above the spar foundation. Based on the analysis of statistics of the relative displacement and velocity of the tower bottom and the spar top, the installation concept with SWATH is found to be of decent performance. Finally, recommendations are provided for future research on this concept, which contributes to developing next-generation installation concepts for bottom-fixed and floating wind farms.

Numerical Investigation of the Automatic Air Intake Drag Reduction Strut Based on the Venturi Effect

Drag reduction by injecting air is a promising engineering method for improving ship performance. A novel automatic air intake drag reduction strut structure based on the Venturi effect is proposed for the high-speed small water-plane area twin hull vessels in the present study. The drag reduction strut can achieve the function of automatic air intake when the vehicle is moving at high speed, and the air inhaled and the incoming flow form bubbly flows to cover the strut surface, effectively reducing the drag of the strut. Considering the longitudinal symmetry of the strut structure, a two-dimensional single-chip drag reduction strut structure is designed to facilitate analysis and a solution. The volume of fluid model is combined with the k-ω SST turbulence model, and a numerical simulation is carried out to investigate the variation of the air inflow, the air volume fraction in the bubbly flows of the strut and the drag reduction rate of the strut for different sailing speeds. The analysis result shows that when the proposed model reaches a certain speed, the external air is inhaled by the strut intake duct, and the bubbly flows are formed with the incoming flow covering the surface of the strut, thereby reducing the drag coefficient. Meanwhile, it is found that as the sailing speed increases, the drag reduction rate of the strut gradually rises and its maximum value reaches about 30%. For high sailing speeds, the drag reduction rate is affected by wave-making resistance so that it gradually declines.

ON THE MACRO HYDRODYNAMIC DESIGN OF HIGHLY EFFICIENT MEDIUM- SPEED CATAMARANS WITH MINIMUM RESISTANCE

A new class of fuel-efficient and environmentally friendly twin-hull vessels is currently under development. Compared to high-speed catamarans, a significant reduction in speed combined with an increase in deadweight tonnes will lead to a highly efficient medium-speed catamaran design. Recently-built conventional and high-speed ferries are compared to each other in terms of length, speed, deadweight and transport efficiency to classify the new design. The goal of this study is to find a preliminary macro design point for minimum total resistance by considering the main particulars of the catamaran vessel: block coefficient, prismatic coefficient and slenderness and separation ratios of the demihulls. Publications containing recommendations towards the optimum hull form parameters for moderate Froude numbers are reviewed and existing experimental data analysed to identify parameters for this new class of vessel. Designs with varied L/BOA-ratios and constant deck area are compared to find configurations of low total resistance for carrying a nominated deadweight at a particular speed, the associated change of the light ship weight has been taken into account. Two different model test series of catamaran models have been considered and their resistance curves agreed to each other. Recommendations are made; with the most important being the vessel should not exceed a speed of Fr = 0.35, with optimal prismatic coefficients around CP ≈ 0.5 and low transom immersion. This study presents the preliminary design of medium-speed single and twin-hull vessels for operations close to hump speed.

Hydrodynamic hull form optimization of fast catamarans using surrogate models

ABSTRACT This paper demonstrates the practical benefit of using efficient computational methods to optimize fast catamarans hydrodynamically. The development of a simplified panel method, which is based on thin ship theory, and the validation of the associated code for the prediction of the calm water resistance of twin-hull vessels is presented. The method was applied in the multi-objective optimization of a fast, zero-emission, battery-driven catamaran by a genetic algorithm, while considering the ensuing design constraints. Results of the study were compared with resistance predictions from a non-linear Rankine panel method and a viscous CFD solver. Moreover, surrogate models were implemented to speed up the optimization process involving several hundred parametrically generated designs. The proposed simplified panel method in connection with a empirical correction for the stern flow proved very valuable in the resistance prediction and hull form optimization of fast catamarans and of slender hulls in general.

Parametric study of buckling and post-buckling behavior for an aluminum hull structure of a high-aspect-ratio twin hull vessel

Metal plates are essential parts of structures such as ship hulls and offshore oil platforms. These plates are typically under compressive axial forces. Hence, one of the main mechanisms for failure and collapse of such structures is buckling of plates. Thus, for safe and secure design, buckling strength of plates should be evaluated. Finite element analysis techniques are perfect tools for this purpose because of the accuracy and flexibility for performing simulations with different variables. In this study, the strength of aluminum plates has been studied using finite element analysis software and it was tried to study the influence of variables such as initial imperfections, plate thickness and aspect ratio on plate strength. It was found that increase in the imperfection magnitude leads to a decrease in the strength of the plate. This is mostly noticed in thin plates because of the plate’s stiffness reduction. Although the plate’s aspect ratio has a slight effect on strength, it has a considerable impact on the failure mechanism. In order to study a combination of plates and stiffeners buckling behavior, part of a high-aspect-ratio twin hull vessel hull structure is assessed under bending moment. It is observed that longitudinal stiffeners at the bottom of the hull in linear analysis undergo the maximum stress, while in non-linear analysis, the maximum stress is spread along with the structure of the deck and bottom, and neutral axis tolerates the minimum stress.

Analisa dan Evaluasi Faktor-Faktor Yang Mempengaruhi Karakteristik Olah-Gerak (MANEUVER) Kapal

The past decade has witnessed a rapid grawth of interest in the development of fast catamaran for various applications. The paper describes the study of interference resistance components on demihull separation. Catamarans or twin-hull vessels may be formed either by connecting two symmetrical demihulls or by splitting a mono hull into two halves to form two asymmetric demihulls. The slenderbody method in Hull Speed- Maxsurf Program was used for predicting the resistance components. The method assumes that the ship's beam is small compared to its length. Effect of resistance interference components on catamaran hull separations are explained and discussed with some work from other published data, which shows good agreement.Keywords : Turning circle, zig-zag, ship, trim, speed.

IDENTIFIKASI RASIO PARAMETER KAPAL PENUMPANG CATAMARAN BERBAHAN FRP

Parameter ratios are important information for the ship designer in the preliminary design stages. They can be used as a tool to identify the main parameter of vessel and their other technical characteristics. The information about parameter ratios of mono-hull vessel is currently available in Naval Architecture literatures, but it is not the case for the type of twin-hull vessel called catamaran. Having conducted technical analysis in this research, it has been identified that parameter ratios of passenger catamaran vessel made of FRP has values of L / B ratio from 2.52 up to 3.7, L / D ratio from 5.25 up to 11:24, slenderness ratio (Lwl/BwL) from 9 up to 12. Other values of various parameter ratios like B/T, D/T, L /√ L, and Displacement/L are also discussed.

On The Macro Hydrodynamic Design Of Highly Efficient Medium-speed Catamarans With Minimum Resistance

A new class of fuel-efficient and environmentally friendly twin-hull vessels is currently under development. Compared to high-speed catamarans, a significant reduction in speed combined with an increase in deadweight tonnes will lead to a highly efficient medium-speed catamaran design. Recently-built conventional and high-speed ferries are compared to each other in terms of length, speed, deadweight and transport efficiency to classify the new design. The goal of this study is to find a preliminary macro design point for minimum total resistance by considering the main particulars of the catamaran vessel: block coefficient, prismatic coefficient and slenderness and separation ratios of the demihulls. Publications containing recommendations towards the optimum hull form parameters for moderate Froude numbers are reviewed and existing experimental data analysed to identify parameters for this new class of vessel. Designs with varied L/BOA-ratios and constant deck area are compared to find configurations of low total resistance for carrying a nominated deadweight at a particular speed, the associated change of the light ship weight has been taken into account. Two different model test series of catamaran models have been considered and their resistance curves agreed to each other. Recommendations are made; with the most important being the vessel should not exceed a speed of Fr = 0.35, with optimal prismatic coefficients around CP ≈ 0.5 and low transom immersion. This study presents the preliminary design of medium-speed single and twin-hull vessels for operations close to hump speed.

Kajian Design Requirfaient Kapal Waterways Provinsi Dki

Design requirement is stmu:fard requirernent tluzt should be met and carried out before introducing akind of newly transportation mode. Sudi matter luzd e-uer been experienced recently bi; the PravinceGovernment of OKI as tnjing to introduce newly transportation rrwde so called waterways besidebus way as a part of macro transportation sd1eme (PTM). During initial. operation trials, the vesselsJuul faced many difficulties and obstacles because of her unsuitable design. In realih;, the existing rivervessels namely KM K.erapu III and KM K.ernpu IV m~re preuiously used for sen transportation. TI1e1;could not fulfill the conditim1 of existing rirer enIironment bemuse their design requirement Juul notbeen m1ailnble and azrried out yeL Draft of tllt'se uessels npproxinmtely 0.6 m Juul become obstacle tooperate in the existing river having depth of about 1 meter or even less. After conducting an analysison design requirement for required river transport, it is finally founded that the suitable river vesselwould have a twin-hull vessel as known as catamaran which has a displacement hull h;pe, made ofFRP, with main dimensions of 9.95m length, 3.20111 width, 1.20m depth, 25knots speed, 25 personscapacitt;, 145/rp, and slenderness ratio I.;b=9. Howerier, dredging effort should be recommended tomaintain river depth at least 1 m or e-uen more and 111ake sure that the proposed riessel may runsmoothly during her operation nnd free fro111 dependenci; from open-closed si;stem of water gate inmaintaining the water depth lend.Keywords: Watenuays, West Flood Canal, Catamaran vessel, Principal dimensions, PravinceGovernment of D KI

An Integrated Methodology for the Design of Ro-Ro Passenger Ships

The present paper provides a brief introduction to the holistic approach to ship design, defines the generic ship design optimization problem and demonstrates its solution by use of advanced optimization techniques. A set of software tools for the parametric design and evaluation of ROPAX vessels has been developed and linked to a multi-objective optimization software, to form an integrated ship-design methodology, facilitating the design space exploration and selection of optimal designs in a rational and efficient way, Zaraphonitis et al. (2007). The present paper focuses on the optimization of design of conventional ROPAX vessels. For an application to high-speed, twin hull vessels, see Skoupas et al. (2009).

Comparative study on the resistance characteristics of mono and split hulls

At present, a number of fast advanced marine vehicles are being developed to meet various functional requirements for both commercial and military purposes. The hull forms of these advanced marine vehicles are classified into mono and multi-hulls. Among the multi-hulls, twin hulls are very popular because of their inherent features such as large deck area, better stability, lower wave-making resistance at high speeds and better safety. Twin hull vessels may be formed either by connecting two symmetrical demihulls or by splitting a mono hull into two halves to form two asymmetric demihulls. The features of the split hull vessel can be governed by many factors such as hull without and with tunnel, tunnel dimension, lateral spacing, and staggered position of the demihulls. Since the propulsive power of any marine vehicle depends mainly on its resistance characteristics, it is required to predict the resistance of the vessel either theoretically or experimentally. In the present study, an attempt has been made to carry out both experimental and numerical investigations on the resistance characteristics of a typical mono hull as well as split hull without and with tunnel and different positions of the demihulls. Using the experimental results, a comparative study on the resistance characteristics is studied.

A New-Generation Motion-Control System for Twin-Hull Vessels Using a Neural Optimal Controller

A new ride control system using a neural optimal controller (NOC) is developed and applied to improve the heave and pitch motion responses of two twin-hull vessels operating in regular head seas. A time domain model for the vessel dynamics in the presence of active fin control is used to simulate the vessel and fin motion responses. An online switching procedure is introduced to select among a number of linear quadratic regulator optimal controllers, designed for different operating conditions of the vessel, to improve the system robustness. Although the online switching offered better robustness and performance characteristics, in between switching operating points, it still remained suboptimal. Therefore, an artificial neural network (ANN) controller was developed as an alternative and initially trained to emulate the same level of control at a number of design operating points, as a NOC. The advantage of this novel application is that practical difficulties in applying an online switching procedure are no longer present and, more importantly, the ANN has been capable of nonlinear generalization to give a near optimal solution away from the trained operating conditions.

Twin-Hull Vessel Motion Control Using a Neural Optimal Controller Design

A Neural Optimal Controller is designed for the reduction of vertical plane motions of a twin-hull vessel over a wide range of encounter wave frequencies in head seas. Improvement in system performance is achieved by dynamic switching between optimal controller designs for different sea conditions. To overcome control problems associated with the switching procedure, a dynamic Artificial Neural Network is used and is initially trained to emulate the same level of control at a number design operating points. The ANN is capable of generalising to give a near optimal solution away from the operating conditions.

Prediction of motion and wave loads of twin-hull ships

A three-dimensional linearised potential theory associated with a cross-flow approach for taking viscous effects into account is presented for the prediction of motion and dynamic structural responses of twin-hull vessels travelling with forward speed in regular waves. Comparisons between theoretical and experimental results are shown for the motion responses and lateral wave loads of an ASR (anti-submarine rescue) catamaran and 3000-ton SWATH (small waterplane area twin-hull) ship. In general, good agreement between theory and experiment is found except for some discrepancies that are believed to be caused by neglect of forward speed effects on free surface.

ON THE HYDRODYNAMIC FORCES OF TWIN-HULL VESSELS

The added mass and damping coefficients for semi- and fully submerged twin cylinders in vertical motion are determined as functions of the oscillation frequency, the cylinder spacing ratio, and the cylinder submergence ratio It has been found that resonance may occur in particular combinations of cylinder spacing and oscillation frequency at which the hydrodynamic mertial and damping characteristics deviate from the trend curves for the case of a single cylinder Justification of using the two-dimensional results to calculate motions of three dimensional twin-hull vessels is discussed It is suggested that, by means of strip theory approach, these results can be used to estimate the hydrodynamic forces for catamaran type vessels in pitch and heave motions.