Hull Shape Research Articles

Underwater Wireless Charging System of Unmanned Surface Vehicles with High Power, Large Misalignment Tolerance and Light Weight: Analysis, Design and Optimization

Wireless charging systems (WCSs) are considered very appropriate to recharge underwater surface vehicles (USVs) due to their safe, flexible, and cost-effective characteristics. The small depth of immersion of USVs allows a WCS operated at an mm-level distance using a dock. Resultant tight coupling between the transmitter and receiver is conducive to high power, yet faces a challenge to alleviating misalignment sensitivity. In addition, considering USVs’ endurance, the weight of a WCS should be strictly limited. In this paper, a 6.0 kW underwater WCS is analyzed, designed, and optimized, which achieves a good balance of power capacity, misalignment tolerance, and onboard weight. A multi-receiving-coil structure is employed, which is crucial to large misalignment tolerance. On this basis, two types of coils adapting the hull shape of USV, viz., curved and quasi-curved coils, are devised and compared in case the hydrodynamic performance of USV is degraded. Finally, the weight of receiver is effectively reduced using bar-shaped ferrite without sacrificing the power capacity of WCSs. The results indicate a merely 8.73% drop in coupling coefficient with misalignment ranging from 0 to 100 mm. Moreover, ferrite use is reduced by 40.48 kg compared to a ferrite sheet, which accounts for 50.28% weight of the receiver.

The influence of the hull representation for modelling of primary ship waves with a shallow-water equation solver

Long-period ship-generated loads have become design-relevant in many shallow and confined waterways. Numerical methods based on depth-averaged equations have conceptually proven successful to provide the ship wave parameters required for waterway management and design. Yet, the validation of these models remains challenging, due to variations in hull shapes, transient ship-motion during field data collection, and the dearth of published experimental benchmark data. The present study makes use of a new experimental data set to validate novel ship-modelling options in the shallow water equations solver REEF3D::SFLOW, using its free surface pressure extension for predicting long-period ship-generated load. The model predicts the primary wave field and the maximum return current with sufficiently low errors (MAPE) of 9.09% and 23.48%, respectively. A sensitivity study reveals that a simple slender body pressure assumption yields comparable simulation performance compared to a more complex hull-derived pressure distribution. The cross-sectional area of the respective pressure function, rather than the exact pressure function shape, is found to be decisive for the correct prediction of the design parameters primary wave height and maximum return current. Based on a systematic investigation of the ship draft to water depth relation, concise guidance on the choice of appropriate pressure functions is presented.

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

Choosing the right hull shape is important in designing a ship, for example, a U-section or V-section of the hull. The hull shape will affect various aspects, such as design, resistance, seakeeping, structure and production. The ship hull must be properly designed so that it can operate according to the ship’s mission. From the seakeeping aspect of the ship's motion at sea, the difference in the hull shape will result in different motions and dynamic effects such as the slamming phenomenon. Based on the difference in the hull shape cases, this study analyzed the difference in the probability of slamming between the U and V hulls. Both hulls were made based on Formdata and almost all parameters were made the same. Parameters that cannot be forced to be the same are WSA (wetted surface area), (coefficient of waterplane area), and (distance of keel to buoyancy), where those parameters determine the difference in the results. The calculation of RAO (operator amplitude response) was obtained using the strip theory method which assisted by Maxsurf Motion software. The results became the input for the calculation of the slamming probability. The study results show that the U hull has a higher probability of slamming occurrence than that of the V hull, with the difference in values ranging from 20% to 35%. Therefore, the U hull will get more frequent slamming loads, so it has the potential to have a higher structural failure (fatigue) than that of the V hull.

Analisys of Hull Shape Art, Speed, Resistance, Power Using Holtrop Method On A Vessel With DWT 12,335 Ton

A general cargo vessel carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. General cargo vessels are equipped with cargo cranes to facilitate the loading and unloading of cargo. This study aims to determine the relation between speed, resistance, and power using the Holtrop method on vessels with a DWT of 12,335 Tons. The ship was modelled using shipping software, and then validated the results with Holtrop mathematical calculations. Holtrop method for calculating tankers, general cargo, fishing vessels, tugs, passengers, containers, and frigates By using the main dimensions of the ship with Length Over All (LOA) 129.8 m, Length Between Perpendicular (LBP) 110 m, Length On Load Waterline (LWL) 112.75 m, Breadth (B) 18 m. height (H) 9 m, Draft (H) 7.2 m, Speed (V) 12.5 Knots. Tests were carried out on Maxsurf Software by calculating resistance and obtaining a graph that displays the relationship between power and speed and resistance and speed.

CFD Study on Hydrodynamic Performances of a Planing Hull

The scope of the present study is to investigate the effects of various geometrical hull features, such as tunnels, spray rails and whiskers on the hydrodynamic performance of a high-speed planing hull. The criteria being tested to emphasize the boat performance are the total drag, sinkage and trim angle. In addition, the decomposition of the resistance into viscous and wave-making resistance are taken into consideration. The study starts with a validation test against experimental data in order to accentuate the capability of the Computational Fluid Dynamics CFD simulation to accurately predict the total drag and trim angle of the initial form. This is later followed by a verification study based on the Richardson Extrapolation method with a grid- and time-step-convergence test in order to predict the numerical errors during the simulation. After establishing the simulation parameters regarding the proper grid size and time step, the comparative study takes place for five hull shapes and two whisker configurations while the boat is sailing at eight different speeds. The assessment of the hydrodynamic flow parameters is evaluated compared to the initial form in order to investigate the influence of the geometry change on the hydrodynamic performances of the boat. Validation of the numerical results showed the reliability of the CFD simulation to accurately predict the drag and trim angle of the boat, while the comparative study revealed that the total drag can be reduced by up to 9%, especially at higher speeds.

Analisys of Hull Shape Art, Speed, Resistance, Power Using Holtrop Method On A Vessel With DWT 12,335 Ton

The ship's resistance affects the selection of the main engine of the ship, especially the bulk carrier ship, which has a significant block coefficient. This study aims to obtain ship resistance with the Holtrop method on bulk carrier ships with a DWT of 30,000 tons. Holtrop method for calculation of tanker, general cargo, fishing vessel, tug, passenger, container, and frigate by using the main dimensions of the ship with Length Between Perpendicular (LPP) 175.27 m, Length on Load Waterline (LWL) 177.95 m, Breadth (B) 24.33 m. height (H) 14.5 m, Draft (T) 10.4 m, Speed (V) 14.5 Knots. Based on computerized results for a speed of 14.5 knots, the ship resistance value is 481.0 KN.

Environmental Inefficiencies of Short Sea Shipping Vessels by Optimization Processes Based on Resistance Prediction Methods

Fulfilment of the progressive environmental normative involves a singular challenge for Short Sea Shipping (SSS), since it must maintain its competitiveness versus other transport alternatives. For this reason, over the last decade SSS vessels have been the subject of numerous analyses, in terms of operative research, and optimizations, from the marine engineering standpoint. Despite widespread awareness about the impact of a vessel’s resistance on environmental performance, many of the previous analyses were based on resistance prediction methods with low accuracy levels. This fact necessarily involves deviations regarding the expected sustainability of vessels. This paper attempts to quantify (in monetary terms) the environmental consequences due to this low level of accuracy. To meet this aim, it analyzes the environmental performance of an SSS feeder vessel, which was obtained from an optimization process based on standard resistance prediction techniques, when its propulsion power requirements for sailing at optimized speed were assessed through the Reynolds Averaged Navier–Stokes method in Computational Fluid Dynamic simulations. The findings show that standard resistance prediction methods without consideration of hull shape must be avoided, not only in the optimization process, but also for operative research, especially in free sailing analysis.

Hull Form Optimization of Fishing Vessels by Adoption of Stern Wedge and Bilge Keel

The most recent ships incorporate a number of significant design enhancements to improve the vessel’s seaworthiness. Bulbous bow, bilge keel, stern wedge, stern tunnel, spray rails, and others are examples. A stern wedge is a small modification of the buttock lines aft of station 19 1/2. The use of this hull design feature on small high-speed planning craft for the purpose of improved powering performance is an accepted naval architectural practice. However, its use on fishing vessels is uncommon. A bilge keel is a marine gear that reduces the tendency for a ship to roll. Hull shape modifications such as bilge keel can potentially increase safety by reducing roll motions. These enhancements have not been adopted or evaluated on fishing vessels, despite the fact that they have been employed on seagoing ships. The installation of bilge keels on fishing vessels was found to have a significant influence on the roll motion of the vessels, boosting their safety and efficiency. When compared to normal trawlers, the installation of bilge keels increased roll period by at least 40% and reduced roll amplitude by 16%.

Research on the bubble sweep-down mechanism and suppression scheme of the research vessel

Vessels will encounter the phenomenon of bubble sweep-down when sailing in the ocean, which seriously affects the accuracy of underwater detection and resource exploration. In addition, the installation of defoaming attachments will affect the resistance performance of the ship. It is significant for a scientific research vessel to study the mechanism of bubble sweep-down and propose a bubble suppression scheme considering the ship's resistance characteristics. Detached-Eddy Simulation (DES) Shear Stress Transfer (SST) k-ω model combined with the Discrete Element Method (DEM) is used to simulate the process of microbubbles sweeping down to the ship's bottom under the influence of the flow at the bow of the scientific research vessel, and the deflection effect of the fairing on the bubbles, to carry out a mechanical analysis of the bubble sweep-down phenomenon. The results show that the bubble movement is closely related to the characteristics of the bow flow, the bubble's trajectory was related to the vessel speed and the bubble starting position, and the bubble at the bottom of the bow was easier to sweep down to the bottom of the ship. The fairing was a defoaming attachment with excellent resistance performance, which can physically block the air bubbles and strengthen the bottom vortex structure to change the bubbles' trajectory. Exploring the bubble sweep-down mechanism and the suppression scheme can better serve the design of the hull shape and defoaming attachment of scientific research ships.

Design limits for wave energy converters based on the relationship of power and volume obtained through multi-objective optimisation

Wave energy conversion can have a significant role in the transition to a net-zero energy system. However, cost reductions are still required for this technology to be commercially competitive. To achieve commercialisation at a reasonable expense, disruptive innovations at early stages of development need to be enabled. Thus, to explore more of the design space, design limits need to be defined. Although physical limits, such as the maximum capture width and the Budal upper bound, have been defined, more realistic limits considering the variability of the resource, device dimensions and the actual hydrodynamic behaviour of different shapes can help provide further insights. This is relevant to both technology developers and funding bodies wanting to identify potential areas for innovation. In this study, the use of multi-objective optimisation is proposed to explore these limits, by investigating the optimal relationship between average annual power production and device size. This relationship depends on resource level, mode of motion used for power extraction and hull shape. The obtained fundamental relationships fall within the existing physical limits, but provide further insights into the impact of different factors on these limits. This allows for a more direct comparison with the performance of state-of-the-art wave energy converters.

Interval optimization design of a submersible surface ship form considering the uncertainty of surrogate model

The integrated design of the ship form is a key issue in the design of submersible surface ship (SSS). In the simulation-based design (SBD) framework, lack of sample data leads to uncertainty in the surrogate model. In this paper, first, a hull cross-section shape modification technology, the self-fusion method, was used to change the ship form, and a fourth-order response surface model was introduced to establish surrogate model of hydrodynamic performance. Second, total resistance in the surface condition and one at a diving depth of 0.48 m were selected as the optimization targets. Third, an automated computing platform was developed to integrate the modules to improve computing efficiency and accuracy. Finally, to explore the adaptability of the ship form scheme, the interval optimization analysis method was introduced into uncertainty optimization. Among them, the interval variable was the surrogate model accuracy, and the targets were the minimum median and the minimum radius of the weighted resistance of cross-domain cases. A two-layer nested optimization system was chosen. Results show that resistance of the optimal SSS was reduced. The interval optimization results were compared with the deterministic optimization results, and the feasibility of hull shape interval optimization was verified.

Monohull or Twin hull Shape Selection Based on the Performance of Hull Planning on Fixed Displacements

The selection of the hull shape below the waterline becomes very important to improve performance and minimize emission during the design stage of the fast boat hull. To understand the performance comparison between the monohull and twin-hull of the same length and width, an analysis was carried out on an 8 m fiberglass ship with Maxsurf. Performance analysis was carried out with Hydromax for hydrostatic performance and ship stability and Hullspeed to analyze the performance of ship resistance and power. Hydrostatic Wetted Surface Area and transverse metacenter radius for the monohull were 13.883 m2 and 1.486 m, while a catamaran shows 12% to 24% higher WSA and 2% to 3% higher BMt compared to a monohull. The resistance and power of the ship at 40 knots for monohull were 24267.07 N and 1116.09 HP. In contrast, the catamaran shows up to 74% increase. Stability arm and radius of gyration show as follow: 0.297 m and 0.631 m for a monohull, while a catamaran shows up to 140% higher max GZ and 222% GMt. The results of this study can be used as a reference for determining the use of a monohull or catamaran hull in the early stages of a fast boat design.

CFD Optimisation of the Longitudinal Volume Distribution of a Ship’s Hull by Constrained Transformation of the Sectional Area Curve

Abstract The paper presents a proposal for a formalised approach to hull shape optimisation with respect to total resistance, by fine-tuning longitudinal volume distribution. An algorithm for automated modification of the hull is presented, allowing for varying the sectional area distribution with a negligible influence on the resulting displacement. Computational fluid dynamics (CFD) solver STAR-CCM+ and computer computer-aided design (CAD) software NX were used to search the optimal volume distribution of selected parent shapes, with respect to total resistance. The bow part and the aft part were optimised separately. The resulting resistances of the selected optimal shapes were then verified by means of scale model tests, realised in the towing tank at the Maritime Advanced Research Centre (CTO) S.A. A noticeable gain in total resistance was achieved and confirmed by experimental tests. The proposed approach seems to be a promising method for relatively quick parametric optimisation of the designed hull shapes; it is also applicable for generic CFD optimisation studies.

Adjoint node-based shape optimization of free-floating vessels

The paper is concerned with a node-based, gradient-driven, continuous adjoint two-phase flow procedure to optimize the shapes of free-floating vessels and discusses three topics. First, we aim to convey that elements of a Cahn–Hilliard formulation should augment the frequently employed Volume-of-Fluid two-phase flow model to maintain dual consistency. It is seen that such consistency serves as the basis for a robust primal/adjoint coupling in practical applications at huge Reynolds and Froude numbers. The second topic covers different adjoint coupling strategies. A central aspect of the application is the floating position, particularly the trim and the sinkage, that interact with a variation of hydrodynamic loads induced by the shape updates. Other topics addressed refer to the required level of density coupling and a more straightforward—yet non-frozen—adjoint treatment of turbulence. The third part discusses the computation of a descent direction within a node-based environment. We will illustrate means to deform both the volume mesh and the hull shape simultaneously and at the same time obey technical constraints on the vessel’s displacement and its extensions. The Hilbert-space approach provides smooth shape updates using the established coding infrastructure of a computational fluid dynamics algorithm and provides access to managing additional technical constraints. Verification and validation follow from a submerged 2D cylinder case. The application includes a full-scale offshore supply vessel at mathrm{Re} = 3 times 10^8 and mathrm{Fn} = 0.37. Results illustrate that the fully parallel procedure can automatically reduce the drag of an already pre-optimized shape by 9–13% within approx,{mathcal{O}}(10,000-30,000) CPUh depending on the considered couplings and floatation aspects.

An efficient and accurate approach for zero-frequency added mass for maneuvering simulations in deep and shallow water

An overall increase in ship sizes in conjunction with a general decrease in ship powering has increased the relevance of reliably predicting a ship’s maneuvering performance. These predictions rely often on mathematical models based on modified Taylor series expansion, where nonlinear multivariate algebraic polynomials that require hydrodynamic coefficients are determined from physical or numerical planar motion mechanism (PMM) tests. The added mass coefficients are needed for a fast and accurate simulation. For maneuvering simulations, these added mass coefficients should be obtained for zero frequency. Despite the advance of high-performance computing, numerical PMM tests based on solving the unsteady Reynolds-averaged Navier–Stokes equations is time-consuming and often not suitable for practical design-related investigations. Furthermore, hydrodynamic coefficients obtained from PMM tests are frequency-dependent. An alternative to numerical PMM tests consists of steady numerical tests. This kind of analysis requires much less computing time and effort for the users. However, the acceleration-dependent hydrodynamic forces and moments cannot be derived from these steady computations. Here we introduced a fast and accurate procedure to obtain water depth-dependent zero-frequency added mass and added moment of inertia. Using Euler Equations, we impulsively accelerated the ship hull over only one time step. We validated our method against an analytical solution for an ellipsoid. We performed systematic computations of added mass and added moment of inertia for two benchmark containerships, a benchmark tanker, and a cruise ship, thereby demonstrating the effects of water depth on added mass for different hull shapes.

Development of a Six Degree of Freedom Velocity Prediction Program for the foiling America’s Cup Vessels

Abstract Since the introduction of hydrofoils to the Moth sailing class in the early 2000’s foiling has become increasingly popular in sailing from windsurfers to large 75’ foiling monohulls. The last 3 America’s Cups have been competed on hydro foiling vessels. Design programs such as Velocity Prediction Programs (VPP) have become a key asset to America’s Cup teams to allow for the optimisation and testing of designs before manufacture. Presented is the development of a Six Degree-of-Freedom (6DoF) Quasi-Static Velocity Prediction Program (SVPP) and Dynamic Velocity Prediction Program (DVPP) for the 35th and 36th America's Cup foiling AC50 Catamaran and AC75 Monohull. The models have been validated against race data from the 35th and 36th America’s Cup showing good correlation for a wide wind range of 8 to 22 knots. The paper presents how the AC50 SVPP was used for analysis on the impact of Rudder Rake Differential (RD) on overall performance, and predicting the optimal wind range for use of the light and heavy weather dagger boards on the AC50 Catamaran. The AC75 SVPP and DVPP were used to analyse the affect of hull shape and the main foils’ fixed angle-of-attack (AOA) on time-to-fight and peak velocity to determine optimal foil setup and pitch angle when foiling. The SVPP and DVPP use XFLR5 software suite to model the foils. Experimental data for a T-foil tested in the Australian Maritime College towing tank facility has been used to predict viscous and free surface effect adjustments to the predictions from XFLR5.

Development of a solar-powered small autonomous surface vehicle for environmental measurements

Nowadays, the use of autonomous surface vehicles has increased in popularity. Autonomous surface vehicles can be adapted to perform water quality measurements, water contamination and hazards detection, garbage collection, aquatic animal population control, shore control, and other applications. This paper shows the novel construction of a small solar-powered autonomous surface vehicle. The vehicle was manufactured of composite materials of natural origin. It was equipped with an electric engine powered by ultralight photovoltaic panel, and a set of sensors and actuators used for autonomous operation and measurements of such factors, as pH, turbidity, purity, and oxygen content in water. The investigations carried out have been divided into three main parts. First, the geometry of the proposed autonomous surface vehicle was modelled using computational fluid dynamics and optimal shape of hull and deck was determined. Then, a dedicated construction of the photovoltaic panel was developed and tested under real conditions. The maximum power generated was 41.7 W when solar radiation was 850 W/m2. The matched power related to the area of 1 m2 was higher by 9.7% – 34.3% compared to other tested market-available panels. Finally, simulations in the TRNSYS software were carried out to determine the operational parameters of the developed autonomous surface vehicle under different operating scenarios. Simulations showed that the operation scenario of the autonomous surface vehicle significantly affects its primary energy consumption due to the energy supplied from the grid to recharge the system after each day of operation. The change in location can increase the primary energy savings, since among the investigated locations the primary energy saving ratio varied between about 30 and 50%. The analysis pointed out that the developed construction of the solar-powered small autonomous surface vehicle is a really promising solution and can be considered as an addition or replacement to the actual available water quality monitoring systems.

HULL SHAPE OPTIMIZATION OF SMALL UNDERWATER VEHICLE BASED ON KRIGING-BASED RESPONSE SURFACE METHOD AND MULTI-OBJECTIVE OPTIMIZATION ALGORITHM

Small underwater vehicles have unique advantages in ocean exploration. The resistance and volume of a vehicle are key factors affecting its operation time underwater. This paper aims to develop an effective method to obtain the optimal hull shape of a small underwater vehicle using Kriging-based response surface method (RSM) and multi-objective optimization algorithm. Firstly, the hydrodynamic performance of a small underwater vehicle is numerically investigated using computational fluid dynamics (CFD) method and the value range of related design variables is determined. The mesh convergence is verified to ensure the accuracy of the calculation results. Then, by means of the Latin hypercube sampling (LHS) design of simulation, the Kriging-based RSM model is developed according to the relation between each design variable of the vehicle and the output parameters applied to the vehicle. Based on the Kriging-based RSM model, the optimal hull shape of the vehicle is determined by using Screening and MOGA. As results, the vehicle resistance reduces and volume increases obviously.

Analisys of Hull Shape Art, Speed, Resistance, Power Using Holtrop Method On A Vessel With DWT 12,335 Ton

A general cargo vessel carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. General cargo vessels are equipped with cargo cranes to facilitate the loading and unloading of cargo. This study aims to determine the relation between speed, resistance, and power using the Holtrop method on vessels with a DWT of 12,335 Tons. The ship was modelled using shipping software, and then validated the results with Holtrop mathematical calculations. Holtrop method for calculating tankers, general cargo, fishing vessels, tugs, passengers, containers, and frigates By using the main dimensions of the ship with Length Over All (LOA) 129.8 m, Length Between Perpendicular (LBP) 110 m, Length On Load Waterline (LWL) 112.75 m, Breadth (B) 18 m. height (H) 9 m, Draft (H) 7.2 m, Speed (V) 12.5 Knots. Tests were carried out on Maxsurf Software by calculating resistance and obtaining a graph that displays the relationship between power and speed and resistance and speed.

Лайнер «Нормандия» как образец стиля ар деко

The article is dedicated to ocean liners, the ambitious projects of the 1930s. The Interwar period was the golden age of transatlantic shipping, primarily due to technical improvements, for example, increased engine power and changes in ship hull shape. However from an artistic point of view, liners also proved to be an important field of application. Many European architects, sculptors, and decorators were involved in the design of the exterior of the liners and their interiors. Most of the masters who participated in the development of a special “liner style” were practitioners of art deco. The spectacular, varied art deco proved to be the most appropriate style, corresponding to the problems which had been set before the artists by the client companies. The subject of the research is to identify the relationship between the “liner style” of the 1930s and art deco, determining the place of the transatlantic liner projects in the culture of the XX century. The object of the research is the design conceptions in general, as well as works of art in the interiors of the liners. The author’s aim is to demonstrate the high importance of these projects for the understanding of the Art Deco era, to characterize the complex approach of masters to the design of liner exteriors and interiors, to consider and compare the most outstanding design solutions. The research methodology includes historical and descriptive, comparative methods, cultural, historical, and culturological approaches. The main attention in the article is given to the French “Normandy”, a recognized example of this style. To expand the context and the possibility of generalization, the focus is also made on two English liners: “Queen Mary” and “Queen Elizabeth”. Among the artists the author points special attention to a French master, Jean Dunant. Dunant’s panels made for the Normandy cigar lounge are considered examples of a decorative style, inspired by the exoticism of archaic or Oriental cultures.