High-speed Monohull Research Articles

Study of the Lift Force Induced by An Interceptor on A High-Speed Mono-Hull: The Affecting Factors and Estimation Formula

Study of the Lift Force Induced by An Interceptor on A High-Speed Mono-Hull: The Affecting Factors and Estimation Formula

The method of navigation performance optimization analysis for high speed monohull ships

This paper is based on the drag resistance test data of the high-speed monohull model, a mathematical model for comprehensive optimization of the navigation performance of a high-speed monohull taking into account the rapidity, maneuverability, seakeeping and static performance of the ship is constructed. The optimization calculation software based on particle swarm, standard genetic algorithm and growth mechanism genetic algorithm is designed and written. Taking a high-speed monolithic sea-going ship with a displacement of 1500 tons and a large inclination-measuring single propeller as the object of discussion, the comparison of optimization methods, the comprehensive navigation performance of different ship types and the sensitivity analysis of design variables are carried out respectively. It provides a practical approach and an effective and practical scientific method for analysis and evaluation of how to maintain the comprehensive optimal navigation performance of high-speed monohull ships. At the same time, it provides a way to quickly evaluate the comprehensive performance of similar high-speed monolithic ships in the preliminary design stage, and can also obtain the model diagram with the best comprehensive performance through this software or method, which is useful for shortening the preliminary design cycle of the ship and improving the design quality of the ship. It has important reference value.

Three-dimensional simulation and evaluation of the hydrodynamic effects of stern wedges on the performance and stability of high-speed planing monohull craft

This study analyzed the hydrodynamics of a high-speed monohull craft model through increasing its longitudinal stability to improve its performance. First, a high-speed planing monohull craft was simulated using computational fluid dynamics. The free surface was analyzed using a three-dimensional volume of a fluid model. The modeled craft with two degrees of freedom was solved using the overset technique for dynamic mesh. For verification, the results of this study were compared with those of an experimental test performed in the laboratory. Accordingly, it was found that the experimental and numerical results were in good agreement. The modeled craft also showed longitudinal instability at a speed of 8 m/s (equal to the speed of sailing). To eliminate this longitudinal instability and subsequently improve the longitudinal performance, craft stern wedges with triangular sections were added in three modes to examine their effects on the resistance and stability of the craft using computational fluid dynamics. Moreover, the results showed that due to the reduction of trim to about 42%, the longitudinal instability was removed at a constant speed, and as a result the longitudinal performance of the craft increased while the total resistance decreased.

Hull forms of small high-speed wave-piercing monohull crafts and hydrodynamics study

Wave-piercing design is a revolution in hull design for small high-speed boats to operate in adverse sea conditions. To study hydrodynamics of the small high speed wave piercing monohull craft systematically, four typical small high-speed wave-piercing monohull crafts were developed, and validated CFD methods were adopted to calculate hull resistances and motions. The resistances and hull motions of these high-speed wave piercing monohull crafts in calm water and waves were obtained and compared. Obvious operating differences can be observed. High-speed wave piercing monohull crafts with slender and twisted planing hulls have smaller resistance at high speed, but the dynamic effects increase as sea conditions worsen. The high-speed wave-piercing monohull craft with a slim multi-chine hull maintains in waves for softer hull motions but suffers the disadvantages of larger resistance. The high-speed wave piercing monohull craft with a triangular hull shows no obvious advantages compared with the other types.

Model tests on resistance and seakeeping performance of wave-piercing high-speed vessel with spray rails

The resistance and seakeeping performance of a high-speed monohull vessel were investigated through a series of model tests in a towing tank. The hull had a slender wave-piercing bow, round bilge, and small deadrise angle on stern. Tests on the bare hull in calm water were first conducted and tests on spray rails followed. The spray rails were designed to control the flow direction and induce a hydrodynamic lift force on the hull bottom to reduce trim angle and increase rise of the hull. The maximum trim of the bare hull was 4.65° at the designed speed, but the spray rails at optimum location reduced trim by 0.97°. The ship motion in head seas was examined after the calm water tests. Attaching the rails on the optimum location effectively reduced the pitch and heave motion responses. The vertical acceleration at the fore perpendicular reduced by 11.3%. The effective power in full scale was extrapolated from the model test results and it was revealed that the spray rails did not have any negative effects on the resistance performance of the hull, while they effectively stabilized the vessel in calm water and waves.

Investigation of hydroelastic effect in analysis of high-speed craft

Hydroelastic effect in bottom slamming problem of high-speed craft is one of the most challenging issues in structural design. In this paper, numerical method is used to investigate the hydroelastic effect in bottom-water impact analysis of high-speed monohull craft. Slamming with two viewpoints of rigid and elastic structures (hydroelastic effect) is modelled by coupled computational fluid dynamic (CFD) and finite element method (FEM) techniques. The results showed that considering hydroelastic effect, especially in high-impact speed, reduces the structural deformations and stresses compared with quasi-statistic analysis. The effect of different parameters, such as boundary condition, plate properties, wedge deadrise angle, and impact velocity in slamming problem, was investigated. The results for aluminium and steel plate with the same bending strength showed that dynamic characteristic of plate material is a major parameter in hydroelastic analysis result. Finally, a simplified method is used to apply the effect of hydroelasticity in bottom plate design. This work is hoped to advance the hydroelastic analysis art in bottom structural design of high-speed monohull craft.

The Optimization Analysis of Navigation Performance and Structural Properties of the High-Speed Monohull Ship in River

Abstract The authors use the weighting summation of rapidity and maneuverability as the sub-objective function of ship performances; By using the weighting summation of static and dynamic properties as the sub-objective function, The weighting summation of these 2 sub-objective functions is just the general objective function. In this paper, a parallel multi-processing genetic chaos algorithm(PM-C-FGA) has been put forward based on fuzzy method, genetic algorithm and chaos algorithm. This algorithm applied effectively to optimize the navigation performance and structural configuration of high-speed mono-hull ship in river.

Broaching prediction of a wave-piercing tumblehome vessel with twin screws and twin rudders

The new intact stability criteria which are under development at the International Maritime Organization (IMO) are required to cover a broaching phenomenon, well known as a great threat to high-speed vessels which can lead to capsizing. Some reports exist which demonstrate that their numerical models can predict a highly nonlinear phenomenon of broaching. However, additional validation studies are needed for unconventional vessels, in addition to conventional ones, to develop direct stability assessment methods for the new intact stability criteria. In this research, we selected as the subject ship a wave-piercing tumblehome vessel with twin screws and twin rudders, a design expected to be one of a new generation of high-speed monohull ships. Firstly, a series of captive model tests were conducted to measure the resistance, the manoeuvring forces, the wave-exciting forces, the heel-induced hydrodynamic forces, and the roll restoring variation for the unconventional tumblehome vessel. Secondly, the existing mathematical model which had been developed for broaching prediction of conventional vessels with a single propeller and a single rudder was extended to unconventional vessels with twin propellers and twin rudders. Finally, comparisons between numerical simulations and the existing free running model experiments were conducted. As a result, it was demonstrated that fair quantitative prediction of broaching is realised when the rudder force variation, the roll restoring variation and the heel-induced hydrodynamic force for large heel angles are taken into account.

Experimental verification of the linear and non-linear versions of a panel code

In the proposed paper numerical calculations are carried out using two versions of a three-dimensional, timedomain panel method developed by the group of Prof. P. Sclavounos at MIT, i.e. the linear code SWAN2, enabling optionally the use of the instantaneous non-linear Froude-Krylov and hydrostatic forces and the fully non-linear SWAN4. The analytical results are compared with experimental results for three hull forms with increasing geometrical complexity, the Series 60, a reefer vessel with stern bulb and a modern fast ROPAX hull form with hollow bottom in the stern region. The details of the geometrical modeling of the hull forms are discussed. In addition, since SWAN4 does not support transom sterns, only the two versions of SWAN2 were evaluated over experimental results for the parent hull form of the NTUA double-chine, wide-transom, high-speed monohull series. The effect of speed on the numerical predictions was investigated. It is concluded that both versions of SWAN2 the linear and the one with the non-linear Froude-Krylov and hydrostatic forces provide a more robust tool for prediction of the dynamic response of the vessels than the non-linear SWAN4 code. In general, their results are close to what was expected on the basis of experience. Furthermore, the use of the option of non-linear Froude-Krylov and hydrostatic forces is beneficial for the accuracy of the predictions. The content of the paper is based on the Diploma thesis of the second author, supervised by the first one and further refined by the third one.

Experimental verification of the linear and non-linear versions of a panel code

In the proposed paper numerical calculations are carried out using two versions of a three-dimensional, time-domain panel method developed by the group of Prof. P. Sclavounos at MIT, i.e. the linear code SWAN2, enabling optionally the use of the instantaneous non-linear Froude-Krylov and hydrostatic forces and the fully non-linear SWAN4. The analytical results are compared with experimental results for three hull forms with increasing geometrical complexity, the Series 60, a reefer vessel with stern bulb and a modern fast ROPAX hull form with hollow bottom in the stern region. The details of the geometrical modeling of the hull forms are discussed. In addition, since SWAN4 does not support transom sterns, only the two versions of SWAN2 were evaluated over experimental results for the parent hull form of the NTUA double-chine, wide-transom, high-speed monohull series. The effect of speed on the numerical predictions was investigated. It is concluded that both versions of SWAN2 the linear and the one with the non-linear Froude-Krylov and hydrostatic forces provide a more robust tool for prediction of the dynamic response of the vessels than the non-linear SWAN4 code. In general, their results are close to what was expected on the basis of experience. Furthermore, the use of the option of non-linear Froude-Krylov and hydrostatic forces is beneficial for the accuracy of the predictions. The content of the paper is based on the Diploma thesis of the second author, supervised by the first one and further refined by the third one.

Stability and safety analysis of the air-lifted catamaran

The air-lifted catamaran (ALC) is an innovative fast marine transportation concept, comprising the application and variation of a new, skirtless air cushion and air-lubrication, thus rendering it a hybrid between catamaran and surface effect ship (SES). Its features and capabilities are beyond current conventional high-speed monohull and catamaran. The present paper presents pertinent studies on stability concerning this craft, including dynamic stability, stability in turning and directional stability. The stability analysis takes into account air compressibility in the cushion, and is carried out in time domain. Some simulated results are presented and discussed, and requirements for design and operation of the craft based on IMO HSC Code 2000 are briefly outlined.

Analysis and Prediction of Slamming-Induced Loads of a High-Speed Monohull in Regular Waves

In recent years, an important trend in the shipbuilding industry has been the increase in the length and speed of high-speed crafts, thus demanding lighter structures. High-speed vehicles with their increased flexibility are more likely to be excited by impulsive loads, such as slamming, which has been extensively studied and discussed by the scientific community. Nevertheless, ship design still demands plain and reliable procedures (numerical and/or experimental) to evaluate the time-dependent global loads in structural dynamics. In this paper, the aim is to explore the possibility of combining the conservation of fluid momentum with the two-dimensional numerical estimation of the effective wetted length in order to improve the prediction of the impact loads without losing the simplicity and efficiency of analytical methods. In order to evaluate the prediction capability of the proposed formulation, the numerical computation of the slamming force is based on processing the model test data relative to the incoming waves and rigid-body motion, and the attained results are compared with the hydrodynamic force experimentally identified. The presented analysis is applied to the slamming tests in regular head waves of a segmented model, supported by an elastically scaled beam, of a fast ferry. By using the slamming load obtained with the theoretical model, the elastic response in terms of bending moments is computed and compared with that provided by direct measurement with strain gauges. Finally, the uncertainty analysis relative to both numerical and experimental results is performed.

High-speed catamaran or monohull? How do you choose?

A decision-making tool has been developed to aid designers when confronted with the choice between two different hull form configurations for a particular route. It incorporates both economic and technical issues, which are the two major components to influence the comparison and evaluation of vessels. A number of technical factors have been taken into account including resistance and powering, passenger comfort and structural configuration; they have different weightings depending on the vessel's operational requirements. The use of the system is demonstrated by way of a case study for a prospective ferry route in South Australia. Conclusions are drawn on its performance and recommendations made for future development.

A Numerical Study of the Resistance of Transom-Stern Monohulls

Experimental data for the wave profiles behind a series of transom-stern ship models has been re-analyzed to provide convenient and accurate regression formulas for the ventilation of the stern and the length of the transom hollow. Predictions of the wave resistance and, hence, the total resistance can now be improved by using this approach, together with the traditional thin-ship formulation for resistance. However, the accuracy of these predictions is improved further if one also considers that there must be a minimal effective hollow length based on the flow behind the backward-facing step. These theories, together with the use of form factors, are applied to a series of fourteen high-speed monohull vessels. It is shown that these methods provide a high degree of predictive accuracy.

スケグによる高速船の針路安定性改善

This paper describes the improvement of course-keeping ability of a ship by attaching the skegs. The ship was designed as a high speed monohull with 40 knots by water jet propulsion system, however, the remarkable course-keeping instability appeared unfortunately. To improve the course-keeping ability, the skegs with As/(LT)=1/50, where As is the total skeg area, L the ship length and T the draft were designed. The captive model tests such as the resistance test and circular motion test were carried out to capture the hydrodynamic force characteristics for the ship with and without skegs. Based on the experimental data, maneuvering simulations such as 15/15 zig-zag maneuver and 30deg turning were made to investigate the effectiveness of the skegs. Through the simulations, we found that skegs with As/(LT)=1/33 are needed for improving the course-keeping ability of the ship. It was confirmed that the skegs are effective in the wide speed range from slow to high near 40 knots by oblique towing test for various ship speed.

On the numerical prediction of seakeeping and of structural loads of high-speed vessels

The applicability of an efficient 3D numerical method for the evaluatfion of the seakeeping performance and structural loads of advanced high-speed vessels is investigated. A semi-empirical approach to account for the viscous flow effects on ship's behavior at speed is presented and discussed. Numerical results are compared with model tests for two high-speed monohull vessels with satisfactory agreement.

Seakeeping Analysis of a High-Speed Monohull With a Motion-Control Bow Hydrofoil

The seakeeping performance is studied of a foil-assisted high-speed monohull vessel using a state-of-the-art three-dimensional Rankine panel method. The vessel is equipped with a bow hydrofoil acting as a passive heave and pitch motion-control device in waves. The formulation of the seakeeping of ships equipped with lifting appendages is developed, and the mechanisms responsible for the reduction of the heave and pitch motions of high- speed vessels equipped with hydrofoils are studied. The sensitivity of the heave and pitch motions on the longitudinal position of the hydrofoil is studied. It is found that the most efficient location for the hydrofoil is at the ship bow leading to a 50% reduction of the root mean square values of the heave and pitch motions in a Joint North Sea Wave Project (JONSWAP) spectrum. Several extensions of the analysis of the present paper are discussed. They include the reduction of the roll motion of high-speed vessels, the design of optimal active motion-control mechanisms, and the coupling of the hull form and lifting appendage design for high-speed monohull vessels.