Hull Configurations Research Articles

Investigation of CO2 emissions reduction for a 150 m electric catamaran by CFD analysis of various hull configurations

Investigation of CO₂ emissions reduction for a 150 m electric catamaran by CFD analysis of various hull configurations

Effect of Platform Configurations and Environmental Conditions on the Performance of Floating Solar Photovoltaic Structures

The growth and development of floating solar photovoltaic (FPV) power plants is a prominent topic within renewable energy technology. One reason contributing to this desired technology design concept is the possibility of land acquisition issues, whereas the usage of the ocean provides a greater technical alternative area. The objective of the research is to present an innovative design for a floating structure, focusing on investigating and comparing the seakeeping performance of several hull configurations: catamaran, trimaran, quadrimaran and pentamaran. The final computational simulation results indicate a linear negative trend in the motion response graphs, particularly in specific significant response values for heave (Global Z), roll (Global RX), and pitch (Global RY), as the hull configuration increases.

Numerical Investigation of Single and Double Steps in Planing Hulls

Incorporating steps into a hull reduces the wetted surface, promoting improved hydrodynamic lift and reduced resistance at high speeds, provided that the step is designed appropriately. Traditional hydrodynamics studies rely on scaled model testing in towing tanks, but numerical tools offer a more efficient alternative. This study focused on investigating the hydrodynamic performance of stepped hulls by modifying the parent hull of the Naples Systematic Series (C1). The Computational Fluid Dynamics (CFD) code SIEMENS PLM STAR CCM+ version 2302 was used for simulations, including four different beam Froude numbers (FrB = 1.13, 2.22, 2.56, and 2.96) and a total of 15 hull configurations with single and double steps. By employing a three-dimensional computational analysis of multiphase flow using Dynamic Fluid–Body Interaction (DFBI) and overset mesh, various performance parameters such as resistance coefficient, dimensionless wetted surface, sinkage, and dynamic trim were analyzed. The accuracy of the CFD results was confirmed through comparison with experimental data and grid uncertainty assessment. The study demonstrated that placing a single step near the transom decreased trim and increased resistance and wetted surface. Conversely, positioning a step in the forward section reduced the trim angle at lower step heights but increased trim at higher step heights in single-stepped hulls. The application of these findings contributes to the design optimization of stepped hulls for enhanced performance in high-speed maritime applications.

Non-uniform inlet flow definition for highly skewed model propeller by geometric partitioning

Ship design involves many calculations to provide a propulsion system with the appropriate speed. Prioritizing speed-resistance calculations affects main engine, gearbox, propeller, and other auxiliary system selection. Here, the propeller is most intriguing. Since the propeller operates in a fluid domain, internal and external factors affect it. Despite being designed for service speed, water flow can affect the efficiency of a propeller at the ship's stern. Under open-water circumstances, a ship's hull affects a propeller's hydrodynamic performance. The effect usually decreases propeller efficiency, so it's important to know how ship hull and propeller design interact before production. To overcome this issue, researchers test towing tanks extensively. Computational Fluid Dynamics, which is efficient and cost-effective, is also commonly used. This study examines the hydrodynamics of a fishing vessel's highly skewed model propeller. The objective of this study was to assess the propeller's efficiency under uniform and non-uniform flow conditions and investigate an alternative method for dividing the inlet area, which has not been studied in the literature. The study has effectively met its goals, producing satisfactory error margins for both operating conditions. This research significantly contributes to understanding the relationship between hull configuration and propeller design, particularly in non-uniform flow scenarios.

Autonomous Design of a Green Sea-Cleaner Boat

This paper addresses the urgent global issue of marine pollution, with a focus on the inadequacies of traditional cleanup methods and the promising potential of an autonomous green sea-cleaner boat. The study presents a sea-cleaner boat design with reduced wake-wash, integrated with an autonomous system using visual equipment and LiDAR sensors for precise navigation and debris identification. Parametric studies of catamaran hull configurations show that the Flat-Outside Model exhibits the lowest wave elevation, indicating reduced hydrodynamic force and wake-wash, making it an environmentally preferable option. Additionally, the sea-cleaner boat employs LiDAR for obstacle detection and a camera with a Convolutional Neural Network for efficient debris identification and collection, enhancing operational safety and efficiency. Overall, the autonomous green sea-cleaner boat represents a significant advancement in maritime environmental conservation.

Numerical Study on Resistance of Stepped Planing Hull

A stepped planing hull, also known as a step hull, is a hull modification that reduces the wetted surface area. Although this type of hull has proven effective in several ships, it is still rarely used. The step hull possesses numerous advantages that make it ideal for activities involving small and fast boats. However, regrettably, its full potential remains untapped at present. The purpose of this study was to identify the effect of variations in the angle of the step hull on resistance or drag. The study utilized the CFD method, and three hull configuration models were used at each change in hull step angle of 180º, 210º, 240º, and 270º. Configurations 1 and 2 have similarities in terms of rear hull length (600 mm), hull height (20 mm for configuration 1 and 30 mm for configuration 2), and deadrise angle (15° for configuration 1 and 20° for configuration 2). Configuration 3 has similarities with an 800 mm rear hull, 20 mm hull height, and 15° deadrise angle. It was found that as the Froude number increases, the coefficient of total resistance decreases. Conversely, as the Froude number increases, the resulting resistance also increases. The configuration with the highest resistance value corresponds to the alteration from configuration 2 with a hull step of 180°, and that the alteration from configuration 2 with a hull step of 270° corresponds to the configuration with the lowest resistance value. This study concludes that deadrise angle and the height of the step hull are the main factors that require careful consideration when designing ships that use a step hull. Therefore, this research provides an understanding of the step hull and can serve as a basis for the development of the step hull.

TRPIV experimental study of coherent structures and their burst events in the boundary layer on JBC

Turbulent drag on the hull surface is one of the main sources of drag during the navigation of a ship, which is significantly influenced by the boundary layer's coherent structures. To investigate the evolution and energy transport of the coherent structures, this study applied time-resolved particle image velocimetry (TRPIV) to realise the fine measurement of the flow field at different upstream and downstream positions on the surface of the Japanese bulk carrier (JBC). Finite-time Lyapunov exponent (FTLE), proper orthogonal decomposition (POD) and quadrant analysis were used to conduct a detailed analysis of the coherent structures and their evolution. The results show that the skin friction drag is notably affected by the coherent structures at the turbulent boundary layer of the JBC hull surface and their burst events. In addition, the turbulent energy that enhances the skin friction drag mainly comes from the outward-inward transport in the turbulent boundary layer, and the intensity of fluctuation velocity contained within the burst events also obviously affects the skin friction drag. The results of this study can provide physical evidence for the optimisation design of similar hull configurations, the optimisation design of unmanned underwater vehicle configuration, and the planning of drag reduction strategy.

Design method of combined stiffened pressure hulls with variable-curvature characteristic

This study presents a combined pressure hull design method with variable-section ribs. This method for determining the length-radius ratio of the pressure hull's bearing unit is derived based on the stiffness-matching characteristic of the shell and stiffener. The bearing mechanism of variable curvature stiffened shell is discussed through theoretical derivation and numerical simulation. The design scheme of variable cross-section and the equal-stiffness rib is proposed to address the limitations of outer envelope size and inner space utilization of the pressure hull. Its buckling load is determined by the energy method. The design approach for a new type of stiffened pressure hull is summarized. In addition, the method is verified by the design example and the experiment. The results revealed that the combined variable curvature shells are a superior pressure hull configuration. Compared to the cylindrical stiffened shell, the buckling load of the pressure hull with variable cross-section ribs can be improved significantly (about 26.7%). At the same time, space utilization remains at the original level. The stiffened design technique described in this research based on elastic buckling theory can accurately determine the length-radius ratio of the bearing unit, relying on the design objective with high feasibility.

Numerical investigation of two-dimensional axisymmetric and three-dimensional flow simulations over a benchmark underwater vehicle

Two-dimensional (2D) axisymmetric simulation is an efficient and time-saving computational fluid dynamics (CFD) technique when the body is axisymmetric, and the flow is along the length of the body. In the present paper, this technique is used to investigate turbulent flow around the bare hull configuration of the Defense Advanced Research Project Agency submarine model. Verification and validation of the results are done at three levels. The values of the total resistance, the distribution of the wall shear stress and the pressure on the surface, and the velocity profiles at various distances from the nose are compared with results obtained by using three-dimensional (3D) simulations and experimental results from the literature. The uncertainty in CFD results due to meshing is reported using Richardson Extrapolation. It is shown that the errors are minor, and the savings in computer memory and computation time are tremendous using 2D axisymmetric simulations. Good CFD practices essential for 2D axisymmetric simulations are also presented in this article, which will be helpful for the CFD community to conduct numerical investigations on any other axisymmetric bare hull bodies, such as torpedoes, missiles, submarines, and autonomous underwater vehicles in the future. Finally, the components of drag, coefficient of pressure, and wall shear stress at the highest speed (9.26 m/s) are also obtained using 2D axisymmetric simulation, which has not been previously reported in any other literature. The level of rigor in the 2D axisymmetric simulation reported here is rarely seen in recent literature.

Multiaxial fatigue assessment of floating offshore wind turbine blades operating on compliant floating platforms

Fatigue damage is assessed for blades of floating offshore wind turbines operating on three different hull configurations using two different strain-based methods. Lifetime fatigue damage is predicted by summing damage over a range of wind-wave conditions conforming to a long-term Weibull distribution. The three hull configurations are selected to cover a wide range of rotational stiffness. Nonlinear beam theory is applied to compute the 3-D beam displacements along the turbine blades. Time histories of the resulting beam displacements are converted to maximum principal strains and to normal strains, and each resulting strain is used to compute the fatigue damage to the blade shells. Results show that the two strain-based methods yield different predictions of fatigue lives and locations of fatigue failures. The normal strain method significantly underpredicts fatigue damage compared to the maximum principal strain method. Fatigue of blades on floaters with very low rotational stiffness is found to be worse than on those with moderate rotational stiffness.

Multi-objective optimization of semi-submersible platforms based on a support vector machine with grid search optimized mixed kernels surrogate model

Determination of optimal hull configurations in the semi-submersible platform (SEMI) should account for several objectives. These objectives are pertinent to hydrodynamic performances of SEMI under wave action but also total structure cost. They are often contradictory and cannot achieve the minimum simultaneously. Hence, a group of relative optimal and balanced solutions is introduced as optimization results, called Pareto-optimal solutions. This paper presents a surrogate-assisted technique to seek the optimal configuration of SEMI for minimal heave and roll response and the lightest weight. Design variables samples are generated by means of multidimensional Ladin hypercube design, and then these inputs are employed for hydrodynamic simulation to acquire the response data. To determine the relationship between objectives and hull structure size, Support Vector Machine with Grid Search optimized mixed kernels (SVM-GSM) is constructed as a surrogate model, and triple verification in terms of errors and robustness warrants its reliability. Three categories of Pareto optimal solutions are obtained by Non-dominated Sorting Genetic Algorithm II (NSGA-II), which correspond to three optimal goals. For optimization results, a presented comprehensive verification approach integrates frequency-domain analysis (FD), time-domain analysis (TD), convergence analysis, and main factors screening. This combination renders sufficient and reliable validation to optimization results. Results from FD and TD for SEMI indicate that the optimized effect of Pareto solutions is satisfactory. Besides, the main influence factors in design variables for hydrodynamic response are screened and investigated. Finally, the ranking of the influence degree of each variable is obtained and evaluated. The proposed framework in this paper provides a comprehensive validation idea for the construction of the surrogate model and optimization results for SEMI hull structure optimization.

Optimization of a production semi-submersible hull configuration system based on the hydrodynamic response for a location in Mexican waters of the Gulf of Mexico

A methodology that optimizes the hull configuration of a production semi-submersible system is developed in this study, which minimizes the hydrodynamic response of the hull under extreme environmental conditions. The optimization methodology requires the calculation of the hydrodynamic response of different hull prototypes, and then find the optimal hull configuration using the Genetic Algorithm (GA) method. The hydrodynamic response is obtained using the software SESAM, while the GA method is applied using the genetic algorithm toolbox implemented in the software MATLAB. The optimization process is applied to semi-submersible systems for three different oil productions located in Mexican waters of the Gulf of Mexico and designed for the local environmental contour. Six design variables of the semi-submersible hull system are evaluated within the optimization, including the pontoon width and height, the column width and height, the distance between columns, and the draft. This case study confirms that all the evaluated geometric design variables have a high impact on the most probable maximum response (MPMR) and the weight of the hull.

INVESTIGATION OF HULL STRENGTH OF RIVER SEA CONTAINER VESSEL

River sea vessels are ships for inland navigation and suitable for restricted navigation at sea in regions where, - significant wave height does not exceed 2m, according to Bureau Veritas Rules for the classification of inland vessels. In a container vessel structure, almost the entire deck space is occupied by hatches, leaving a narrow strip of deck plating outboard. This calls for a topside structure of heavy plating or a double hull to provide material in tension, stiffness against lateral and torsional loads, and resistance to buckling in compression when the vessel is in sagging condition. For sea going open deck vessels, torsional loading plays a predominant part to the hull girder strength and for inland navigation open deck vessels; the effect of torsion is rather negligible. Keeping this scenario in mind, the aim of this project is to investigate the hull strength of a river sea container vessel under combined bending and torsional loading to study the effect of torsion on river sea open deck vessel. To perform the strength analysis, firstly, a finite element model is created using Femap with NX Nastran software for the investigated vessel. Therefore, still water and wave loads are calculated using direct calculation. To find out the still water loads Argos software is used and for the wave induced loads potential flow software Hydrostar is used. Next, Finite element model is verified with classical beam theory and thin wall girder theory. Then the effect of various loading conditions on structural response is investigated. After, structural response of different hull configurations are scrutinized under combined bending and torsional loading. Finally, some recommendations are proposed for structural response of river sea container vessel subjected to combined bending and torsional loading.

AERODYNAMIC LIFT FORCES ON MULTIHULLED MARINE VEHICLES

The need for high-speed high-payload craft has led to considerable efforts within the marine transport industry towards a vehicle capable of bridging the gap between conventional ships and aircraft. One such concept uses the forward motion of the craft to create aerodynamic lift forces on a wing-like superstructure and hence, reduce the displacement and skin friction. This paper addresses the specific aerodynamic design of multihull for optimal lift production and shows that significant efficiency can be achieved through careful shaping of a ducted hull, with lift-to-drag ratios of nearly 50 for a complete aerodynamic hull configuration. Further analysis is carried out using a hybrid vehicle stability model to determine the effect of such aerodynamic alleviation on a theoretical planing hull. It is found that the resistance can be halved for a fifty metre, three hundred tonne vehicle with aerodynamic alleviation travelling at 70 knots. Results are presented for a candidate vessel.

CFD Analysis into the Resistance of Trimaran with Longitudinal Sidehull Adjustments

There has recently been a surge in demand for multi-hull vessels for military and commercial purposes. The need for multi-hull ships increase from the necessity to balance speed and cargo requirements. Among others, the trimaran is one such hull type. The current study performs a CFD resistance analysis for trimaran as a parameter range of feasible hull forms based on the NPL systematic series. The resistance of trimaran hull shapes are calculated using CFXTM, a commercial CFD code that belongs to ANSYS. The trimaran model was tested at one fixed transverse separation (S/L=0.2) together with 3 longitudinal separations, R/L=0, 0.25, and 0.5, at different Froude numbers (based on length) from 0.2 to 0.6. Testing on the individual hull is also carried out to quantify the effect of resistance interference on the trimaran configuration. The CFD simulation results indicate that the trimaran model with side hulls parallel to the stern (R/L=0) has the least resistance. The interference effect of resistance on Trimaran with R/L=0, 0.25, 0.5 are 2.8%, 4.6%, 6.8% as opposed to non-interference trimaran model, respectively. These findings provide an approach for appropriately selecting the trimaran model with longitudinal side hull configurations.

Numerical Investigation of High-Reynolds-Number Air-Ventilated Water Flow under Solid Body with Surface Geometry Variations

Air-ventilated cavities formed under or around the hulls of marine vehicles can reduce water drag. Hull configurations with partial air ventilation where air cavities reattach to body surfaces are of special practical interest, since the required air supply rates to achieve significant drag reduction can be made rather low. However, formation and stability of such air cavities are sensitive to the hull geometry and operational conditions. In this study, an attempt is made to numerically simulate one setup with a partial air cavity that was previously tested experimentally at high Reynolds numbers, above 50 million. A computational fluid dynamics software Star-CCM+ has been employed for numerical modeling. Stable and unstable states of the air-cavity setup, characterized by long and collapsing air cavities, respectively, were modeled at two air supply rates near the stability boundary. Numerical results were similar to experimental data at the optimal water speed for the tested geometry, when a long air cavity was sustained at a minimal air supply rate. For water speeds that were substantially higher or lower than the optimal case, a stable cavity could not be maintained with small air supply rates for the given hull geometry. Numerical simulations demonstrated how alterations of the body surface could help sustain long air cavities across a broader speed range using air supply rates that were similar to the optimal case. These findings suggest that morphing hull surfaces can potentially be used for control of drag-reducing air cavities and expand the viable operating range for their application to marine vehicles.

Problems and technical solutions of capture fisheries in Eastern Indonesian waters

Problems concerning capture fisheries in Eastern Indonesian Waters cover the existing of fishes at sea, continuity of catching activities, the use of fishing gears, safety aspects, market, price and recent situation of pandemic Covid-19. This conditions have the impact on decreasing of economy aspect of local fishermen. The purpose of this research is to develop facility of capture fisheries and other related technical aspects to overcome the existing problems and to keep the continuity of fishing activities. The research started by initial field survey by the authors. In addition, related problems from other references are used as input design parameters. Design process end-up with the blue prints and the design specifications of fishing boats and fishing gears. The research was continued with construction of boats prototype, training for the fishermen and sea trials. The results of research were prototypes and design specifications of several types of fishing boats. Fishing boats with hull configurations (monohull, catamaran and trimaran) and fishing gears specification were fixed due to boat operational aspects. In addition, the results of study concerning safety aspect and ship operation in period of Pandemic Covid-19 are presented in this paper. Recommendations of results of this study are presented for future development of fishing boats for local fishermen.

Numerical analysis of marine propellers low frequency noise during maneuvering

In this paper the effects of maneuvering motion on the hydro–acoustic performance of a marine propeller in behind–hull configuration is investigated. Velocities induced by ship motions markedly modify the inflow to the propeller and hence noise sources and emission can be different with respect to the rectilinear motion, that traditionally is exclusively considered during the design process. This problem is crucial from a practical perspective, because the success of many types of operations at sea relies on the stealthy qualities of the vehicle and, moreover, for it can provide an additional aid to preserve marine life. In this paper this topic is tackled by a multidisciplinary approach that involves the use of hydrodynamic solvers and an acoustic analogy based on the Formulation 1A by Farassat. In particular, the noise sources, input to the acoustic analogy, are computed by an hybrid approach consisting of CFD simulation to obtain the inflow to the propellers and a blade element momentum theory solver (BEMT), enhanced with linear, partially cavitating hydrofoil theory to account for cavitating conditions too. The test case is a modern twin screw ship undergoing rectilinear advance and turning maneuvers at two different rudder angles for a moderate speed at FN=0.265.

Drag Analysis of Three Rudder-Shaped Like Bodies

This paper presents an investigation of Rudder Shaped-Like (RSL) hull configurations with low-drag characteristic using the resistance model tests and numerical analysis. The new design of the floating platform using three hulls with a self-manoeuvring system as Unmanned Surface Vehicle (USV) and capable of collecting the same data as a hydrography boat is needed. This platform was designed with three hulls placed in a triangle position in the form of rudder shape and vertically placed as a slender body shape using National Advisory Committee for Aeronautics (NACA) 0012 profile. This provides the low-drag characteristic to USV. The results from the experimental and numerical analysis revealed that a larger configuration distance between three hulls leads to a reduction in resistance of the same speed. This result may help to accomplish the required concept design related to low-drag and minimum power operation.

Numerical Investigations on the Resistance and Longitudinal Motion Stability of a High-Speed Planing Trimaran

The planing trimaran is a novel kind of aerodynamic alleviated marine vehicle and possesses a unique hybrid hydrodynamic and aerodynamic characteristics. In this paper, to investigate the hull behavior of a planing trimaran under the effect of tunnel forces, the tunnel and demihull are treated as appendages mounted on the slender main hull. Numerical simulations were carried out for planing trimaran and a monohull which was built according to the main hull configuration. Mesh convergence studies were implemented based on the public experimental data of a similar planing trimaran. Calculated results show that the presence of tunnel and demihull could decrease the resistance of the main hull and improve the longitudinal motion stability at high speeds. Flow evolutions of waves, velocity vector, wetted length and lift distribution were performed to explain the variation of the tunnel lift and its moment and their influence on hull behavior. Parameter studies on demihull length were carried out as well. It was found that, as the demihull length is increased, the tunnel trimming moment would decrease especially in the final stage of ventilation, making resistance reduced but the motion stability weakened.