Hull Form Research Articles

Development of stealth design systems for advanced submarine hull forms to reduce underwater radiated noise and target strength

The stealth capability of a submarine is the key performance to be considered in submarine design since it is directly related to survivability and operational capability. In this study, a system that can be applied from the conceptual design stage for the submarine shape, including the hull forms and appendages, has been developed by considering the two key components that determine the stealth capability of underwater vessels: underwater radiated noise (URN) and target strength (TS). First, for submarine stealth design considering URN, a design optimization technique was developed that can reduce the high flow noise caused by the interaction between the propeller and the vortex generated in various parts of the hull and appendages. And for submarine stealth design considering TS, shape design technology that can minimize the reflections of active sonar was developed through an evaluation method with high adaptability to shape modifications. Finally, by developing the optimization design procedures that comprehensively cover URN and TS, the optimal shapes and arrangements of sail and rudders that can maximize stealth performance have been derived.

The Hull of a Galleon: An Archaic Construction or a Masterpiece of Ship Design

The Galleon was considered a masterpiece of shipbuilding in the sixteenth century, but from a modern point of view, the shape of her hull looks archaic and primitive. However, how accurate is this perception? Is the hull form of Galleon primitive? What were the reasons for its unique design features? This article investigates these questions by directly analysing the hull’s features from the point of view of modern ship’s theory, as well as from a historical perspective. A careful evaluation of specific design criteria of a typical Galleon, together with analysing a 3D model of its hull on modern software, with further insight for the seakeeping behaviour of Galleon with a comparison to more modern full-rigged ship (Barque of 19 CE), showed that these features were not random, but instead had a good rationale behind it, and served specific and carefully decided functions, required at the time.

Effectiveness of Crew Boat Hull Form on Manouvering Performance

The condition of the crew boat is good hull shape with good operational conditions when maneuvering. In this case, the condition of the waveform at sea will have a significant impact on the ship’s motion. To provide the optimal type of hull, it was developed by conducting several simulations on the ship’s motion. Several simulation conditions were carried out, including analyses of ship speed, the shape of the waves formed, and ship maneuvering. At the simulation stage, several types of hulls were carried out, including the single U-hull, the single V-hull, the trimaran, and the catamaran. The simulation limits the length of the ship but not the width of the ship because the conditions in the multi-hull require sufficient space for its width, so that it can be ascertained that it provides effective and efficient results for the selection of the shape of the hull. The simulation analysis carried out provides a recommendation that the single V hull model gives good results compared to other types of hull selection for crew boat hulls.

Development of propulsion solutions for river-sea ships of the northern Black Sea

Conception of hull form and propulsion design of river-sea ships essentially depends on the restrictions of specific inland waterways. River-sea ships of the Northern Black Sea were historically designed for operation through the locks of European inland waterways of the former Soviet Union. River-sea vessels of the late Soviet Union were designed as simple and technological. After dramatic economical changes the ships of new generation acquired completely different features of general and propulsion design. The vessels had unusually full hull forms and azimuthal thrusters. As is shown in the paper, the full hull forms have sound economic grounds for the considered ship type. However, azimuthal thrusters have controversial features and are not non-alternative. Based on analysis of previous and current propulsion solutions their further development is proposed within the considered ship type. Hull forms designed with specially developed CFD methods are recommended as a further step toward propulsion optimality.

Design-space dimensionality reduction in global optimization of functional surfaces: recent developments and way forward

ABSTRACT In shape optimization of complex industrial products (such as, but not limited to, hull forms, rudder and appendages, propellers), there exists an inherent similarity between global optimization (GO) and uncertainty quantification (UQ): they rely on an extensive exploration of the design and operational spaces, respectively; often, they need local refinements to ensure accurate identification of optimal solutions or probability density regions (such as distribution tails), respectively; they both are dramatically affected by the curse of dimensionality as GO and UQ algorithms' complexity and especially computational cost rapidly increase with the problem dimension. Therefore, there exists a natural ground for transferring dimensionality reduction methods from UQ to GO. These enable the efficient exploration of large design spaces in shape optimization, which, in turn, enable global optimization (possibly in a multidisciplinary and stochastic setting). The paper reviews and discusses recent techniques for design-space dimensionality reduction in shape optimization, based on the Karhunen-Loève expansion (equivalent to proper orthogonal decomposition and, at the discrete level, principal component analysis). An example is shown and discussed for the hydrodynamic optimization of a ship hull.

Frictional Resistance Increase Due to Hull Roughness: An Analysis of the Hull Form Parameters Influence

An awareness of the drag increase brought on by biofouling's roughness on the ship hull is one technique to cut emissions aboard ship. However, predicting the increased drag on ships poses significant challenges. When predicting the rise in frictional resistance brought on by roughness, the hull is considered flat. In fact, ship hulls have a variety of shapes, and it is not certain whether this is a factor influencing the magnitude of the increase in resistance due to roughness. In this article, the effect of the hull's form parameters— (ratio of length per breadth), (coefficient block), and (Length of center buoyancy)—on the increase in frictional resistance brought on by roughness have been investigated. The method used to calculate the ship resistance is Computational Fluid Dynamics (CFD) simulation, complemented by roughness modelling using the wall function approach method. The Design of Experiment (DOE) method has been used to vary the shape of the hull model as a variation of the test specimen in this study. The verification and validation tests have been carried out on the CFD simulation results, where the results have been compared with proven empirical methods. Based on the study results, the value of frictional resistance and increased frictional resistance () of all specimens has shown no significant difference in value, evidenced by the variance values, ranging only 1.57-2.1%. Thus, these results prove that the increase in frictional resistance due to roughness is sufficient to assume the ship's hull as a flat plate. The other finding is that roughness can also increase the pressure resistance, and hull shape parameters also contribute towards changes in the value of resistance.

Power Prediction Method for Ships Using Data Regression Models

This study proposes machine learning-based prediction models to estimate hull form performance. The developed models can predict the residuary resistance coefficient (CR), wake fraction (wTM), and thrust deduction fraction (t). The multi-layer perceptron and convolutional neural network models, wherein the hull shape was considered as images, were evaluated. A prediction model for the open-water characteristics of the propeller was also generated. The experimental data used in the learning process were obtained from model test results conducted in the Korea Research Institute of Ships and Ocean Engineering towing tank. The prediction results of the proposed models showed good agreement with the model test values. According to the ITTC procedures, the service speed and shaft revolution speed of a ship can be extrapolated from the values obtained from the predictive models. The proposed models demonstrated sufficient accuracy when applied to the sample hull forms based on data not used for training. Thus, they can be implemented in the preliminary design phase of hull forms.

Design and Build of an Autonomous Catamaran Urban Cargo Vessel

This study introduces a novel test bed, named the Maverick, which aims to advance the field of autonomous inland waterborne freight transportation and facilitate its eventual implementation. More specifically, the Maverick focuses on operating in small waterways within urban areas, aligning its application scenario with the European project AVATAR. The hull form of the Maverick was selected to be a catamaran, as it offers several advantages, including a large open deck area, high transverse stability, and excellent maneuverability at low speeds. The Maverick is equipped with two 360-degrees-steerable azimuth thrusters, one at the bow and one at the stern. This configuration makes the Maverick over-actuated, and offers more advanced motion control possibilities compared to conventional rudder-propeller actuated vessels. The Maverick is composed out of modular building blocks combined with a flexible interface, which enables it to accommodate diverse control terminals for future developments. Furthermore, to illustrate the feasibility of the Maverick within an urban context, this study also includes results of several trail tests. The interactive communication framework that was successfully employed in the autonomous sailing experiment is introduced. The Maverick offers a versatile platform for testing and developing a wide range of technologies in situation awareness, autonomous sailing, smart waterway logistics, and other interconnected domains. Therefore, this innovative research vessel can pave the way for the development of a new freight transport mode within European urban areas, contributing valuable experiences to the field.

Guideline for Preliminary Design Phase of Trawler Type Yachts

Yacht design is a multidisciplinary process that consists of set of iterative sub-processes. The main aim of the whole process is to reach the optimum design that satisfies not only the engineering-related requirements, but also the user’s expectations. In the preliminary design process, determination of the type and the main dimensions of the yacht according to the user’s preferences is followed by the processes such as the general arrangement plan, determination of the hull form and superstructure design, estimation of hydrostatic and hydrodynamic characteristics, etc. In this research, it is aimed to obtain a parametric design framework which enables to reach hull form characteristics, layout parameters and resistance estimation values with respect to various speeds, only by using only LOA of trawler type motor yachts. In this content, 26 trawler type motor yachts were investigated and their hull were modeled for speed-resistance calculations. As a result of the research, graphics and tables were presented that allow to reach the characteristic parameters, which are important in terms of design and engineering, by using only the LOA value in the preliminary design phase of the trawler type motor yachts.

Study on the Manoeuvring Performance of a Fishing Vessel Based on CFD Simulation of the Hull Forms and Rudder Shapes

To evaluate manoeuvring performance of merchant ships, the mathematical modeling group (MMG) or computational fluid dynamics (CFD) simulations are used. However, it is difficult to use the MMG to evaluate the manoeuvring performance of fishing vessels, thus research using CFD simulations is necessary. Also, since the course-changing and turning ability is crucial in fishing operations, a rudder design suitable for fishing vessels is necessary. This study designs a rudder using National Advisory Committee for Aeronautics (NACA) airfoil sections and evaluates its manoeuvring performance. A CFD model is used to evaluate the manoeuvring performance of the fishing vessel, and turning and zig-zag tests are conducted. The effectiveness of using CFD simulations based on Reynolds averaged Navier-Stokes equations to assess the manoeuvring performance of fishing vessels was validated. No significant difference was found in the manoeuvring performance for hull forms and rudder designs for course-changing ability. However, the original hull form showed superior turning performance. Among five rudders with varying aspect ratios and shapes, the rudder with 5.5% aspect ratio had the best turning performance. Regarding the rudder design for fishing vessels, NACA airfoil was employed, and a rudder aspect ratio of 5.5% based on the immersed hull side area is recommended.

Matlab Implementation using Holtrop and Mennen Method of Bare Hull Resistance Prediction for Surface Combatant Ship Coupled with CFD

Holtop’s & Mennen’s method is one of the most widely used technique in resistance and powering prediction for tankers, general cargo ships, container ships and combatant surface ships. Holtrop’s Statistical Analysis method is utilized, as in comparison to the other options, more complete and closer to the actual results. The main purpose of this paper is to develop a Matlab application using Holtop’s & Mennen’s method for studying and research the total resistance of DTMB 5415 combatant ship. The solid modelling is developed using Maxsurf. The computational fluid dynamic (CFD) technique is applied to analyze the hydrodynamic behaviour of hull form and predict the total resistance (Rt) to provide a description of the other prediction methods. The simulation process was executed using ANSYS software based on fluid flow (STAR-CCM+) solver. The variation of computational grid used in computation is SST (Shear Stress Transport) coarse and fine mesh size for hull speed up to 32 kn. RT resulted from CFD computation is validated with results from Holtrop that has been developed by Matlab implementation. The larger the grid meshing size, the better the validation of the results. The CFD technique demonstrated good agreement with Holtrop formulae in predicting the (RT) of DTMB 5415

Non-dimensional Hydrodynamic Coefficients Determination of a Derived-Submarine Bare Hull Form

The hull of the marine vehicle can be optimized based on the target one or more purposes. One of the most frequent purposes is the form optimization to obtain the most suitable form in terms of resistance. When it comes to energy efficiency, optimizing the vessel's form in terms of resistance means less fuel consumption. However, it is thought that the effect of the optimized form on other dynamics in the marine vehicle should also be investigated. Resistance coefficients were obtained for this purpose by constructing various bow and stern forms for a simple submarine form. The resistance coefficients of both the submarine and the form derived from this submarine were validated again in this study since different software programs were used in the previous study. These dimensionless resistance coefficients obtained for various velocities were compared to each other and the experimental data. Furthermore, the static drift analyses are performed to obtain the sway force and yaw moment at various attack angles. The dimensionless hydrodynamic coefficients, such as Y_v' and N_v’, have been calculated with fitting a curve to the values of sway forces and yaw moments. The non-dimensional hydrodynamic coefficients differences calculated for the submarine and derived bare hull are close to each other when compared in terms of maneuvering derivatives.

NUMERICAL ANALYSIS OF MODIFIED ANGLE OF ENTRANCE AND DUCKTAIL ADDITION OF THE 1,500 GT RO-RO FERRY HULL VALIDATED WITH SHIP MODEL RESISTANCE TEST

The main problem of ferry ships is maintaining the speed due to ship resistance. There are many efforts to reduce the resistance by modifications of them. This study aims to reduce resistance due to modification of the hull form on the bow Angle of Entrance (AoE) and ducktail addition at the transom stern. The object of the research is a 1,500 GT ro-ro ferry. The AoE minimizes wave resistance and improves flow patterns, while the ducktail reduces the negative effects of the circulation zone on the wetted transom so that waves and wake are reduced. Computational Fluid Dynamics (CFD) was used to analyze these modifications. The final results of the numerical simulation are then verified by the ship model resistance test in the towing tank. Tests were conducted in calm water conditions at a draft of 3.30 meters with a speed variation of 10 - 18 knots. The results show that with the combination of AoE and Ducktail, at ship speeds of 13 to 18 knots, the reduction in resistance from CFD ranges from 13.13% - 16.69% while the experimental results range from 16.00% - 16.54%. While separately the AoE modification is between 8.89% – 12.19% and ducktail is 3.12% -3,62%.

Development of a small-sized tanker with reduced greenhouse gas emission under in-service condition based on CFD simulation

In the present study, the hull form and appendage of a 6.5 k DWT tanker was improved to reduce greenhouse gas emissions in the in-service navigation condition. The conventional hull form of the 6.5 k DWT tanker has been designed in terms of performance in the ideal condition of a calm-sea. On the contrary, the performance of a ship in the in-service condition should take the added resistance due to wind and waves in the real sea into consideration. In order to reduce the added resistance due to waves, the bow hull form was modified to have a sharper entrance with increased length between perpendiculars. This was intended to ensure that the waves follow the curved bow surface more smoothly, thereby reducing the added resistance due to waves. The stern hull form was also modified to have V-shaped section shapes to reduce viscous pressure resistance. In addition, the flow control fins were optimized in terms of position and angle of attack. The added resistance of the resulting hull form was then analyzed numerically in regular wave with a varying wavelength ratio λ/Lpp=0.5∼2.0. The added resistance in regular waves was subsequently integrated with respect to the wavelength to obtain the added resistance in irregular waves. Finally, by combining it with the sea state occurrence probability, the daily fuel oil consumption (DFOC) was able to be calculated for the actual in-service routes for the tanker. The entire process of hull form modification and evaluation was conducted with free-surface CFD simulation in the presence of regular waves. A series of model tests was undertaken to confirm the improvements of the optimal hull form over the original in terms of performance in waves as well as calm-sea performance. The resulting DFOC and daily CO2 emissions for the optimal hull form in the in-service conditions was found to be reduced by 14.8%. Furthermore, the calm-sea DFOC and CO2 emissions were also improved by 15.6%.

Study of a hull form optimization system based on a Gaussian process regression algorithm and an adaptive sampling strategy, Part II: Multi-objective optimization

Ships have a wide variety of performance specifications and experience complex navigation conditions. Thus, an efficient numerical optimization system for general hull forms must be able to deal with multi-objective optimization problems. Based on a Gaussian process regression (GPR) algorithm and an adaptive sampling strategy, the authors have developed a single-objective optimization system, SBO-MSE + LCB, which is more efficient than the conventional simulation-based design (SBD) optimization system. However, the application of this system to hull form multi-objective optimization problems presents problems such as excessive new samplings, insufficient exploration of new sample points, and unsuitable convergence criteria. To solve the above problems, we first propose an adaptive sampling strategy based on the idea of spatial clustering. The strategy not only effectively controls the number of sampling numbers at each iteration in the SBO-MSE + LCB optimization system but also enables new sample points to achieve the multi-objective efficient exploration of optimal solution sets for optimization. Then, from the perspective of the convergence and diversity of Pareto optimal solution sets, we design adaptive sampling convergence criteria suitable for multi-objective optimization problems. Based on this, we enable the SBO-MSE + LCB optimization system to solve multi-objective optimization problems and verify its applicability with several cases for which the multi-objective mathematical optimization is performed. Finally, we use the SBO-MSE + LCB multi-objective optimization system and the SBD optimization system to optimize the total resistance coefficient of a deep-sea aquaculture vessel at the scantling and ballast drafts. The results show that the optimization efficiency of the SBO-MSE + LCB multi-objective optimization system is improved by 33.33% from the SBD optimization system for similar optimization performance, proving its advantage in efficiency in practical applications.

Adaptive grid deformation method for CFD application to hull optimization

This work introduces a new grid deformation method for an efficient CFD-based optimization of ship hull forms. The method uses a two-level point transformation technique to manipulate grid points with a small number of design points. At the first level, generic B-spline is employed to transfer grid points based on movements of control points sampled inside a control box, ensuring accuracy and smoothness of surface modification. At the second level, Radial Basis Function with Wendland’s C2 continuity is adopted to interpolate movements of control points based on relatively few design points. It is shown to be effective in preserving good mesh quality and efficiency. The method is applied to the deformation of hull surfaces for ship models KVLCC2 and KCS, and to investigate the effects of bulbous bow on calm-water resistance with fixed Lpp. A regression model is proposed for ship length, location of buoyancy, wet surface area, and displacement. Numerical results show that the present method is well-suited for CFD-based hull form optimization with better efficiency.

Drag reduction and power optimization due to an innovative, toroidal hull form of an AUV

The use of unconventional design has become a norm for mission-specific underwater autonomous craft. Geometrical characteristics and drag optimized shapes of single-hulled underwater vehicles are known since 1970s and a few significant improvements have been possible since then. These are mostly related to the efficiency of a wake adapted propeller, positioned at the stern in wake of the hull. In a novel effort, when the propeller is integrated into the craft at center-line, and the hull in its entirety is designed to act as the duct, the drag of the hull is further reduced. This craft uses a toroidal hull form that distributes payload axi-symmetrically around an internal ducted thruster. The craft is designed to operate at an economic cruise speed of 2kn. The power consumption is optimized to achieve an endurance of over 500 miles through this implementation of a ducted thruster. The hydrodynamic characteristics of the new toroidal hull are compared to those of a reference design which is slender and conventionally shaped. This conventional design is intended for the same volume and dimensions of payload. A reduction of 13% in drag from the first to final design iteration is achieved. This reduction in drag is due to a higheer effective length to thickness ratio of the ducted AUV, quantified in terms of a new parameter defined as Ih . The reduction of the wetted surface area also contributes to the drag optimization. The article shows that the shape of the leading edge of the toroidal hull becomes important to achieve low drag. The process of design and optimization using CFD, with the most appropriate turbulence models is detailed. The beneficial effect of the acceleration induced in the flow at the leading edge and trailing edge of the hull by the integrated thruster is studied and explained with the help of CFD results.

Experimental Study on the Ice Resistance of a Naval Surface Ship with a Non-Icebreaking Bow

With the shrinking of Arctic sea ice due to global climate change, potential access to Arctic waters has increased for non-typical icebreaking or strengthened ships. Numerous studies have been conducted on hull form designs and ice resistance predictions for ships with typical icebreaking bows, but published research for ships with non-icebreaking bows in ice is still rare. The objective of this study was to investigate the ice resistance of a naval surface ship with a non-icebreaking bow through model tests in an ice tank. The naval surface combatant concept DTMB 5415 was used as the ship model. The tests were conducted under different levels of ice thicknesses and speeds. During the tests, the total resistance of the model ship was measured, accompanied by monitoring of the ice load at the stem area with a flexible tactile sensor sheet. Compared with the test results of icebreaker models in former studies, the total ice resistance, as well as the stem ice load, of the present ship was significantly higher. The ice crushing resistance component in the stem area accounted for more than 60% of the total resistance in the ice. Discussions on the applicability of a semi-empirical formula for predicting the ice resistance of the present ship are also presented. Keinonen’s formula was found to be relatively more consistent with the predictions produced by model tests, and a preliminary modification was proposed to obtain more accurate predictions.

The reverse prediction of the ship principal dimensions based on the Kelvin ship waves

This study examines the impact of the ship’s principal dimensions on the steady waves generated by the ship, and practical approaches are subsequently proposed to reverse-predict the ship’s length, width, draught, and related parameters. The ship length Ls and the related Froude number Fr=Vs/gLs are found to relate with the quasi-period of the divergent wave amplitude function. The ship length can be predicted within an accuracy of ±5% overall based on the two-point wake model considered here. The effects of the ship width and the ship draught are different, and a practical method is proposed here to predict the ship width and the ship draught based on the simplification of the Hogner theory. A noteworthy discovery of this research is that the hull form details have a more pronounced impact on the trough of the divergent waves compared to the transverse waves and the peaks of the divergent waves.

Reaching IMO 2050 GHG Targets Exclusively Through Energy Efficiency Measures

_ Maritime transport accounts for around 3% of global anthropogenic greenhouse gas (GHG) emissions (Well-to-Wake). These GHG emissions must be reduced by at least 50% in absolute values by 2050 to contribute to the ambitions of the Paris Agreement signed in 2015. Switching to zero-carbon fuels made from renewable sources (hydro, wind, or solar) is seen by many as the most promising option to deliver the desired GHG reductions. However, renewable energy is a scarce resource that gives a much larger GHG reduction spent within other sectors. This study explores how to reach the IMO 2050 GHG targets exclusively through energy efficiency measures. The results indicate that by combining wind-assisted ship propulsion (WASP) with a slender hull form, fuel consumption and GHG emissions can be reduced by 30–35%, at a negative abatement cost for speeds exceeding 8 knots. Where the cost saving increases with the speed because at higher speeds, the fuel accounts for a higher share of the total cost, which implies that the cost saving goes from zero at 8 knots, to 5% reduction at 11 knots average speed to 14% reduction of total cost with 15 knots average speed. In comparison, GHG reductions through zero-carbon fuels will increase transport costs by 50–200%. Introduction From the first days of our civilization, sea transport has enabled regional and global trades. Today, sea transport accounts for 80% of the global trade measured in ton-miles (UNCTAD 2021) and 3% of greenhouse gas (GHG) emissions measured Well-to-Wake (Lindstad et al. 2021). More than 40% of this sea trade is performed by dry bulkers, making them the real workhorses of the sea. Even though sea transport is energy efficient compared to other transport modes, all sectors need to reduce their GHG emissions by at least 50% in absolute values by 2050 to contribute to the Paris Agreement (UNFCCC 2015). According to Bouman et al. (2017), the desired energy and GHG reductions can be achieved through: Design and other technical improvements of ships; Operational improvements; Fuels with zero or low GHG footprints; or a combination of these.