Yacht Hull Research Articles

Hydrodynamic investigation of wet swimming platform problem for semi-planning motor yachts

One of the main optimization problems for the performance and comfort of yachts is the wet swimming platform problem, also known as the rooster-tail phenomena .And this research presents an investigation using Computational Fluid Dynamics (CFD) method for a real case of an 88 ft. semi-planning motor yacht hull form that encountered this phenomena. First of all, the original hull form was analyzed to define the problem at cruising and maximum speeds, 14 knots, and 24 knots respectively. To solve this problem, modifications to the stern form of the hull were made in a two-step iteration. Initially, the size of the current interceptor was increased with a tunnel wedge. Results of the CFD analysis show that this modification eliminated the wet platform problem and increased the top speed of the yacht. Since the applicability of the wedge to mount is complex and costly, a second analysis with only enlarged interceptors was performed. As a result, the wet platform problem is solved, however, the resistance reduction was slightly lower.

Dynamics augmentation for high speed flying yacht hulls through PID control of foiling appendages

A numerical investigation is conducted in order to identify a PID control loop feedback scheme able to return dynamics augmentation and superior seakeeping characteristics in the application of high speed flying yacht hulls. An existing lumped parameters model based on general unsteady equations of motion is extended and implemented in combination with a regular basic ocean waves model, to conduct parametric studies and predict the overall performances of a specific engine-propelled flying yacht hull, both in calm and rough water conditions. The unsteady behavior of six foiling/maneuvering appendages is investigated, the hydrodynamic characteristics being based on a database generated through the use of computational fluid dynamics methods (CFD) coupled with static/dynamic-mesh schemes. Equations of motion and hydrodynamics are solved numerically by explicit time-integration method. By comparison with control open-loop conditions, the results show the effects of the use of PID controllers in such dynamic systems in terms of seakeeping performances and dynamics augmentation.

Improved estimation of ship wave-making resistance

For the prediction of ship resistance in the preliminary stages of the design process, naval architects often use methods that are less complex and expensive than CFD simulations and experiments. The linear wave-making theory can be used to quickly evaluate wave resistance, although, the theory gives poor estimates for conventional hull forms due to neglecting viscosity. This paper introduces improvements to the original theory by including boundary layer effects through the tangency correction that can handle flow separation. The improvements that account for viscous and nonlinear effects are implemented within Michell’s thin-ship theory to extend its applicability to non-slender hulls, which is validated by numerical simulations of five profoundly different hull forms: the Wigley hull, Series 60, Delft 372, a yacht hull, and the KRISO containership hull. The modified theory yielded more accurate resistance curves compared to the original theory and Holtrop–Mennen’s method, and gave new insight into ship wave-making.

GenYacht: An interactive generative design system for computer-aided yacht hull design

In the present work, a new digital design system, GenYacht, is proposed for the creation of optimal and user-centred yacht hull forms. GenYacht is a hybrid system involving generative and interactive design approaches, which enables users to create a variety of design alternatives. Among them, a user can select a hull design with desirable characteristics based on its appearance and hydrostatics/hydrodynamic performance. GenYacht first explores a given design space using a generative design technique (GDT), which creates uniformly distributed designs satisfying the given design constraints. These designs are then presented to a user and single or multiple designs are selected based on the user’s requirements. Afterwards, based on the selections, the design space is refined using a novel space-shrinking technique (SST). In each interaction, SST shrinks the design space, which is then fed into GDT to create new designs in the shrank space for the next interaction. This shrinkage of design space guides the exploration process and focuses the computational efforts on user-preferred regions. The interactive and generative design steps are repeated until the user reaches a satisfactory design(s). The efficiency of GenYacht is demonstrated via experimental and user studies and its performance is compared with interactive genetic algorithms.

Optimization of Painting Process to Improve Durability of Mega Yacht and Cavitation Erosion Characteristics

The purpose of this study is to investigate the correlation between roughness and adhesion force of each painting step to improve the durability of mega yacht hull painting and to analyze cavitation erosion characteristics according to the number of finish paintings. As a result, the adhesion force of the paint with each painting step was greatly influenced by the surface roughness according to the pretreatment work. However, in some painting steps, sandpaper work that forms the surface roughness was not performed by considering the work efficiency and economic efficiency. On the other hand, the cavitation erosion test presented that cavitation erosion resistance was improved by increasing the cohesion force of the urethane coating itself as the number of coatings increased. We also discussed the cavitation erosion mechanism for the optimized urethane coating. Key words: Roughness, Cavitation erosion, Adhesion force, Urethane coating

Modeling of transient hydrodynamic lifting forces of sailing yachts and study of their effect on maneuvering in waves

The calculation of hydrodynamic lifting forces sustained by a sailing yacht's hull performing maneuvers in regular incident waves is reported. The mathematical model involves the application of the lifting surface theory for transient flows, implemented through the numerical scheme of the vortex lattice method and corrected for linear thickness effects of the simulated body geometry. The mathematical influence of the waves appears through the derivation of the wave potential and it is employed in a kinematic sense via the introduction of an additional inflow velocity component on the lifting surface. Validation with data derived from experiments in calm water showed very good agreement. Additionally, the variation of the side force coefficient while sailing in waves has been quantified in terms of the amplitude of oscillation due to the wave orbital velocities. The formulation is intended to upgrade the respective computational component in a mathematical model previously developed by the authors, for the maneuvering motions of sailing yachts. Parametric studies of maneuvering and course-keeping demonstrate a sensitivity of the yacht to wave steepness and heading angles, with a deficit in sustaining capacity appearing for lower wind speed.

Eye tracking for screening design parameters in adjective-based design of yacht hull

Adjective-based design is a method that translates human perception into design parameters quantitatively in order to achieve better understanding between designers and clients. In this approach, adjectives are used to describe product designs, which are generated via design parameters in terms of geometry. As a requirement of the concept, relations between hull adjectives (e.g., comfortable and aesthetic) and design parameters (e.g., length and width) are learned via a machine-learning algorithm. Nevertheless, the relations cannot be represented by some of the design parameters, although they are in the learning process. This issue shows that the parameters do not impact the adjective choices but add noises to the learning process. Therefore, in this study, visual evaluations are made using eye tracking technology for screening the parameters based on their attractiveness and establishing relations between the attractive ones and the adjectives to enhance quality of the relation representations. Eye tracking is used in perceptual research, which proves the existence of correlations between gaze data and human preferences. The main advantage of eye tracking is that reliable human perception data can more likely be collected compared to the user tests, since the evaluation is based on subjects’ attention rather than applying solely questionnaires that are limited by the question content. In light of the benefits and finding, an eye tracking device is used to collect gaze data, and then, eye tracking tools such as Area of Interest (AOI), scan path, and heat map are used to evaluate attractiveness of the design parameters. Finally, regression analysis is used to represent relations between gaze data of design parameters and the adjectives.

Sampling CAD models via an extended teaching–learning-based optimization technique

The Teaching–Learning-Based Optimization (TLBO) algorithm of Rao et al. has been presented in recent years, which is a population-based algorithm and operates on the principle of teaching and learning. This algorithm is based on the influence of a teacher on the quality of learners in a population. In this study, TLBO is extended for constrained and unconstrained CAD model sampling which is called Sampling-TLBO (S-TLBO). Sampling CAD models in the design space can be useful for both designers and customers during the design stage. A good sampling technique should generate CAD models uniformly distributed in the entire design space so that designers or customers can well understand possible design options. To sample N designs in a predefined design space, N sub-populations are first generated each of which consists of separate learners. Teaching and learning phases are applied for each sub-population one by one which are based on a cost (fitness) function. Iterations are performed until change in the cost values becomes negligibly small. Teachers of each sub-population are regarded as sampled designs after the application of S-TLBO. For unconstrained design sampling, the cost function favors the generation of space-filling and Latin Hypercube designs. Space-filling is achieved using the Audze and Eglais’ technique. For constrained design sampling, a static constraint handling mechanism is utilized to penalize designs that do not satisfy the predefined design constraints. Four CAD models, a yacht hull, a wheel rim and two different wine glasses, are employed to validate the performance of the S-TLBO approach. Sampling is first done for unconstrained design spaces, whereby the models obtained are shown to users in order to learn their preferences which are represented in the form of geometric constraints. Samples in constrained design spaces are then generated. According to the experiments in this study, S-TLBO outperforms state-of-the-art techniques particularly when a high number of samples are generated.

A shape sampling technique via particle tracing for CAD models

In this paper, a shape sampling approach is proposed for CAD products that can be used to suggest innovative product shapes to designers and consumers. These shapes are intended to inspire designers and can be employed during the design process. For a given set of geometric parameters defining the product shapes, parameter relationships (i.e., geometric constraints), and parameter ranges, a particle tracing (PT) algorithm is proposed to find product shapes that satisfy the defined geometric constraints in the shape space. Particles are placed at points in the shape space by minimizing the Audze–Eglais potential energy of the particle positions using a permutation genetic algorithm. They then move until one of the predetermined stopping criteria is met. Particle movement is achieved using a cost function that favors movement towards feasible shapes. By iteratively running the PT algorithm, feasible shapes are obtained. Representatives of these shapes are identified using a k-medoids clustering approach, and such representatives can be used by designers or shown to consumers to customize the product according to their preferences. In this paper, eight CAD models (e.g., car hood, yacht hull, wheel rim) are utilized to validate the performance of the proposed sampling technique. We also compare our technique with related methods.

Learning yacht hull adjectives and their relationship with hull surface geometry using GMDH-type neural networks for human oriented smart design

Several efforts have been made to describe cars by adjectives, however there is no particular work exploring adjectives describing yacht hulls which motivates this study. First, a novel design schema is developed for representing yacht hulls in 3D, which is parametric based and includes several geometric parameters quantifying the hull models. Three surveys are then conducted to learn the relationship between hulls and hull adjectives. In the first survey, yacht models with different geometries are shown to participants to form the hull adjective dictionary. Next, geometric parameters having no impact on the hull adjectives are eliminated via the second survey. Hull adjectives are then matched with yacht hull models via the third survey. The models shown in the third survey are obtained by performing sampling using the Taguchi experimental method. Finally, GMDH-type neural network (GMDH) is applied to the data sets obtained from the third survey to determine the relationships between the hull adjectives and the geometric parameters. GMDH provides mathematical models for each adjective consisting of geometric parameters with coefficients. With the outcomes of this work, we expect that communication between designers and customers can be easier, and adjective based design variations of yacht hulls can be achieved in a shorter amount of time.

A novel design framework for generation and parametric modification of yacht hull surfaces

This paper proposes a new design framework for the parametric design and shape modification of a yacht hull. In this framework, the hull is divided into three regions (entrance, middle and run) and each region is represented separately. In this way, a designer has better design flexibility so that higher design variations of the hull can be achieved. Each region consists of keel line(s), deck line, chine line(s) and station lines that are represented using Bezier curves and these lines are called feature curves. A 3D surface model of a yacht hull is obtained by generating Coons patches using feature curves. Shape operators are also introduced and implemented for the modification of the given hull shape while considering some quality criteria such as hull fairness. Experiments in this study show that a variety of hull shapes can be generated using the proposed design framework with the application of the shape operators.

First record of the non-indigenous isopods Paracerceis sculpta (Holmes, 1904) and Sphaeroma walkeri Stebbing, 1905 (Isopoda, Sphaeromatidae) for Madeira Island

While exploring the presence of non-indigenous fouling species colonizing settlement plates deployed in local marinas in Madeira Island (north-eastern Atlantic Ocean), two non-indigenous species (NIS) of free-swimming crustaceans, Paracerceis sculpta (Holmes, 1904) and Sphaeroma walkeri Stebbing, 1905 (Isopoda: Sphaeromatidae), were detected. Paracerceis sculpta is native to the Pacific Coast of North and Central America and has been introduced into many other regions worldwide. Sphaeroma walkeri is native to the northern Indian Ocean and nowadays is considered one of the most widely ship-transported species globally. Both species were collected in the marina of Funchal, Madeira Island, Portugal, during monitoring surveys in 2015. Moreover, several specimens of S. walkeri were also found in a foreign recreational yacht hull, during a dry dock inspection. These findings suggest that hull fouling is a significant vector for the introductions of marine invertebrates into the Madeira island system.

Optimizing Trimaran Yacht Hull Configuration Based on Resistance and Seakeeping Criteria

An investigation into the optimization of a trimaran yacht, which is equipped with axebow, was carried out numerically. The study was focused on the analysis of resistance and seakeeping which can provide the best performance to the yacht, based on those two criteria. The numerical study used Ansys Fluent code for resistance analysis and seakeeper from Maxsurf for seakeeping analysis. The overall results were compared with published data for validation purposes. The results are believed to be useful for the development of the marine-tourism, which is now growing quite rapidly in Indonesia.

Treatment of industrial exhaust gases by a dielectric barrier discharge

Volatile organic compounds (VOCs) in industrial exhaust gases were treated by a dielectric barrier discharge (DBD) operated with two different mobile power supplies. Together with the plasma source various gas diagnostics were used, namely fourier transform infrared (FTIR) spectroscopy, flame ionization detector (FID) and GC-MS. The analysis revealed that some exhaust gases consist of a rather complex mixture of hydrocarbons and inorganic compounds and also vary in pollutants concentration and flow rate. Thus, analysis of removal efficiencies and byproduct concentrations is more demanding than under laboratory conditions. This contribution presents the experimental apparatus used under the harsh conditions of industrial exhaust systems as well as the mobile power source used. Selected results obtained in a shale oil processing plant, a polymer concrete production facility and a yacht hull factory are discussed. In the case of total volatile organic compounds in oil processing units, up to 60% were removed at input energy of 21–37 J/L when the concentrations were below 500 mg/m 3 . In the yacht hull factory up to 74% of styrene and methanol were removed at specific input energies around 300 J/L. In the polymer concrete production site 195 ppm of styrene were decomposed with the consumption of 1.8 kJ/L. These results demonstrate the feasibility of plasma assisted methods for treatment of VOCs in the investigated production processes but additional analysis is needed to improve the energy efficiency.

Uncertainty quantification for a sailing yacht hull, using multi-fidelity kriging

Uncertainty quantification (UQ) for CFD-based ship design can require a large number of simulations, resulting in significant overall computational cost. Presently, we use an existing method, multi-fidelity Kriging, to reduce the number of simulations required for the UQ analysis of the performance of a sailing yacht hull, considering uncertainties in the tank blockage, mass and centre of gravity. We compare the UQ results with experimental values.

해양레저 분야 복합소재 적용 : 33피트급 아메리카스컵 훈련용 CFRP 세일링 요트 개발

본 논문에서는 해양레저분야에서의 현재 복합재 적용 현황과 33피트급 아메리카스컵 훈련용 세일링 요트 개발에 대해 기술한다. 항공분야와 달리 해양레저 분야에서의 복합재료는 최근에서야 적용 및 사용이 되기 시작했다. 다양한 해양레저 구조물 중에서도 특히, 아메리카스컵 세일링 경주 요트는 빠른 속도를 내야 하기 때문에 경량화 및 높은 기계적 성능이 요구되고 이에 따라 경주용 요트를 건조함에 있어 탄소섬유의 사용은 필수적이다. 탄소섬유강화 플라스틱 경주용 요트 제작 과정을 정립하기 위해 탄소 돛대와 탄소 요트 선체에 대한 최적화 설계와 생산 공법에 대해 논의되었다. 최종적으로 이렇게 제작된 탄소섬유강화복합재 세일링 요트는 운항시험을 통해 경주용 요트로써의 높은 성능을 보여주었다. The purpose of this paper is to investigate the current trends of composite applications in the marine and leisure fields and to study the development of 33ft class America's cup training CFRP sailing yacht. In the field of marine and leisure, composite materials have been just used to marine and leisure structures, recently. Especially, since the America's cup of sailing yacht racing has required the light weight and high mechanical performance to make a high speed, CFRP have been recognized as the critical material to construct the racing yacht structures. To establish the process of CFRP racing yacht construction, the design optimizations and production methods of carbon mast and CFRP yacht hull were discussed in this paper. Finally, the constructed CFRP sailing yacht exhibited high performance as the racing yacht through the sailing test.

Advancements in free surface RANSE simulations for sailing yacht applications

The analysis of yacht hulls performance using RANSE based free surface simulations has become an accepted approach over the last decade. Access to this technology has been eased by the development of user-friendly software and by the increase of computational power. Results are widely accepted as superior to previous non-viscous approaches and have to compete with towing tank results in terms of accuracy. However, many practical applications suffer from a numerical smearing of the free surface interface between air and water which can be described as numerical ventilation. This problem occurs when the intersection between bow and calm water surface forms an acute angle and is further pronounced if the stem is rounded or blunt. It is therefore especially linked to sailing yacht applications. The problem manifests itself as a non-physical suction of the air–water mixture under the yacht hull, causing a significant under-prediction of viscous resistance. While this is the easily observable appearance of the problem, a second issue is its effect on wave resistance. It can be shown that wave damping is significantly increased, causing a prediction of wave resistance which is also too low. The paper provides a review of the Volume-of-Fluid method. It discusses the resultant implications for practical applications. A remedy to circumvent the problem is described and its impact on the accuracy of the result is shown. Simulations on an identical appended hull with and without interface smearing are compared. Effects on free surface visualization and numerical accuracy are shown. The paper finishes with a thorough verification and validation of a fully appended yacht in accordance with ITTC standards.

Strength Analysis of Yacht Hull Building by VIMP

This paper describes FRP boat hull for specific construction process using the vacuum infusion process, and between the different processing sample strength are compared, and then to get the optimal construction scheme, which can be the reference to the yacht building in the future.

폴리에틸렌 보트의 구조강도 평가에 관한 연구

Boat or yacht hull has been built mainly by FRP composite materials. FRP boat hull manufacturing begins to be restricted after 2000 under international regulation on ocean environment safety. Therefore, alternatives of FRP has been proposed by many boat builders and high strength aluminium is consdiered as its standard material. But, high strength aluminium is very expensive as boat hull material. In this study, Boat hull was built by high density polyethylene and its structural strength was estimated by longitudinal strength test method in small craft. Tensile strength of polyethylene boat hull material is less than tensile strength of FRP boat hull material. But Safety factor of polyethylene boat hull is more than safety factor of FRP boat hull. This results indicate structural integrity and quality control of polyethylene boat is better than FRP boat.

Large yacht hull measurement by integrating optical scanning with mechanical tracking-based methodologies

In the shipbuilding industry, the manufacturing of large yacht hulls is a complex process. Metal hulls are traditionally manufactured by welding pre fabricated large steel panels to form the external superstructure. A surface finishing process is then carried out in order to obtain a final target surface having a smooth curvature. The methodologies manly rely on manual processes based on the measurement of the as built hull shape through simple testing instrumentation. Well-experienced workers are required, and a great amount of time is usually wasted, thus affecting the overall shipyard competitiveness.