Bow Design Research Articles

Bulbous Bow Shapes Effect on Ship Characteristics: A Review

Abstract Hydrodynamic optimization is an effective and robust design method that is indispensable in ship hull form performance. Marine engineering and naval architecture have displayed significant interest in integrating bulbous bows on combatant ships. This review aims to gather and assess the existing knowledge regarding the effects of bulbous bow shapes on the hydrodynamic characteristics of combatant ships in terms of historical background, design principles, and impacts of bulbous bow shapes on ship resistance, ship motion in seaways, squat, and seakeeping performance. The review evaluates the effects of bulbous bow shapes on hull hydrodynamics using computational fluid dynamics (CFD), model testing, and full-scale experiments. The text delves into the complexities of improving hull shape and how the bulbous bow design interacts with many operational factors like draft, speed, and sea conditions. This research offers scholars, naval architects, and marine engineers a comprehensive insight into the intricate effects of bulbous bow shapes on combatant ship performance. It aims to consolidate current material to enhance our comprehension of ship design and operation by identifying knowledge gaps and suggesting future research areas.

Fishing Vessel Bulbous Bow Hydrodynamics—A Numerical Reverse Design Approach

Naval hydrodynamics typically focus on reducing ship resistance, which can be achieved by incorporating a bulbous bow. This feature is commonly used in the merchant fleet and smaller vessels, such as fishing boats, to minimize wave-making resistance. However, it is important to note that the use of a bulbous bow may not always be necessary or effective in all ship designs. In some cases, fishing ship designs may include a bulbous bow that is not optimized due to the use of procedures and methods intended for larger merchant ships or based on past experience. This study examines the effect of different bow designs, including the bulbous bow, on ship resistance in calm water, with a focus on a typical Argentinian trawler fishing vessel. The objective of this research is to assess the hydrodynamics of various designs for a particular ship by modifying its vessel lines. Firstly, the bulbous bow is removed, and then the reduction in ship resistance achieved by the bulbous bow under different load conditions and speeds is evaluated by comparing the vessel with and without the bulbous bow. The numerical analysis is performed using OpenFOAM, and the results are validated through towing tank experiments. This research indicates that the performance of the bulbous bow varies under different conditions. Therefore, it is recommended to conduct an initial study and a full evaluation of the design and operation alternatives.

Investigation of An Inverted Bow on Frigate Hull Resistance

This study discusses the inverted bow design on the combatant hull form. Changes in the shape of the stem angle and flare bow are used as analytical parameters to investigate the ship's performance. Ship resistance and motion will be predicted using the Computational Fluid Dynamics (CFD) approach using the Reynolds Averaged Navier Stokes (RANS) equation and the k-ε turbulence model. The volume of fluid (VOF) method is applied to simulate the change in the free surface between water and air using an overset mesh technique. The ship's movement is limited to sinkage and trim motions, so the movement's accuracy can be predicted. The results revealed that the inverted bow reduced the total resistance by 6.30%, whereas the trim and sinkage showed no significant changes. The breakdown of the reduction ratio showed that friction resistance components were reduced by 10.62%, wave resistance by 44.05%, and viscous-pressure resistance by 45.33%. This highlights the effectiveness of an inverted bow in optimizing wave and viscous pressure, enhancing overall ship performance.

On the genesis of the bow designs from the “Old Buryat” burials

In the paper, the finds of fragments of bows from the “Old Buryat” burials of the 17th–18th centuries from the Baikal region are analysed, and an attempt is made to determine their genesis from the data on their technological features. On the basis of the conventional method of weapon-analysis classification, two types were distinguished by the set of the reinforcing onlays. To understand the missing structural elements, the data is drawn in on more recent fully preserved items produced locally in the 19th — early 20th c. from the museum and private collections from the territory of the Baikal region, since a genetic affinity can be traced between them and the earlier products by the available onlays. This allows one to speak about similar morphological and metric characteristics between the Buryat bows of the 19th — early 20th c. and the objects from the “Old Buryat” burials. In the result of the conducted analysis, the relationship between the distinguished type 1 and items of the 12th–14th cc. of the population of the Ust-Talkinskaya Culture of the Cisbaikalia region has been established by the onlays used and the structure of the wooden base (in comparison with the products of the Buryats of the 17th–18th cc. associated with the bows of the 19th — early 20th c.), on the basis of which it was concluded that the design evolved in the Mongolian period from a local prototype. The type 2 is also associated with ‘Mongolian type’ bows by the presence of the median frontal remiform onlay, although it has the features of Yakut’s ‘Central Asian’ bows (the end frontal straps made of staghorn with a wide and a narrow areas). In the course of the study, it has been revealed that the design of the objects of the 19th — early 20th c., predominantly Transbai-kalian bows of the Selenga Buryats, has features of both the type 1 as well as the type 2, and it evolved from a local basis as a result of the synthesis of the elements of these types, thus combining the features of the northern and local workmanships. In the result, the structures appeared, which were reinforced with long end straps made of staghorn, with a long wide area creating transitional zones, and a short narrow one reinforcing the rigid limb tips. In the Cisbaikalia region, modifications of the type 1 bow were further developed by means of combining materials in the onlays of the transitional zones. All of the recorded bows, in terms of the shape of the ends and transitional zones, are much closer to the Mongolian bows of the 12th–14th c. from the rock burials of Mongolia, than to the Manchurian-Mongolian bows widespread in Central Asia since the 17th c.

Geometric Effect of Bulbous Bows to the Hydrodynamic and the Probability of Slamming on Catamaran

Achieving optimal efficiency, good performance, and cost-effectiveness is the main challenge in ship design. Using a bulbous bow is part of attaining an excellent design to reduce drag and dynamic load caused by waves and slamming. The design of the bulbous bow is commonly determined by shape geometric based on laboratory testing or computer optimization. This article compares the probability of slamming into a catamaran NPL hull without a bulbous bow and with a bulbous bow. Variation of the geometric bulbous bow and its effect on hydrodynamics and slamming was investigated. This study uses a numerical method by CFD software and applies secondary data of model testing on the same object as another researcher. The adjustment of the bulbous bow led to a 15.22–17.07% reduction in wave drag. According to the bulbous bow variant, increasing the linear parameter of the length of the bulbous bow reduces the wave drag and the probability of slamming to 2,9% In the motion analysis of a catamaran without a bulbous bow, the heaving and pitching are more significant than a catamaran with a bulbous bow.

Research on the Shape Optimization of Three-Dimensional Bow

Boat is mainly composed of hull, ship frame, deck, cabin and ship deck building. When people are designing the boat, one key consideration is the shape of the bow in order to decrease the resistance and fuel-consumption. In this paper, theoretical analysis of resistance to bow and the optimization aimed for lower resistance were produced by using COMSOL Multiphysics 6.0. Firstly, a simple and ordinary model of bow is presented. Then, the mathematical and physical model are established by COMSOL. Afterwards, after I exam whether the computational model is effective enough for the further optimization, the calculating results are worked out and I compare them with the common bow’s experimental data, with the purpose of the optimization, the lower resistance, in different conditions such as different ship speed and draft. The polynomial expression of several important section is used to construct the basic outline of the three-dimensional bow with different width, bow length, angle of bow top and the possible maximum and its position. Then, I choose the bow length, angle of bow top and the possible maximum and its position as the optimization parameter. Finally, I reach the conclusion of a better-performing bow design for newer high-speed boat requirements and future studies are discussed.

Retrofit-induced changes in the radiated noise and monopole source levels of container ships.

The container shipping line Maersk undertook a Radical Retrofit to improve the energy efficiency of twelve sister container ships. Noise reduction, identified as a potential added benefit of the retrofitting effort, was investigated in this study. A passive acoustic recording dataset from the Santa Barbara Channel off Southern California was used to compile over 100 opportunistic vessel transits of the twelve G-Class container ships, pre- and post-retrofit. Post-retrofit, the G-Class vessels' capacity was increased from ~9,000 twenty-foot equivalent units (TEUs) to ~11,000 TEUs, which required a draft increase of the vessel by 1.5 m on average. The increased vessel draft resulted in higher radiated noise levels (<2 dB) in the mid- and high-frequency bands. Accounting for the Lloyd's mirror (dipole source) effect, the monopole source levels of the post-retrofit ships were found to be significantly lower (>5 dB) than the pre-retrofit ships in the low-frequency band and the reduction was greatest at low speed. Although multiple design changes occurred during retrofitting, the reduction in the low-frequency band most likely results from a reduction in cavitation due to changes in propeller and bow design.

Investigation on the effect of bow configuration on motion and green water for tumblehome vessels based on cartesian grid finite difference method

The special bow design of the tumblehome vessel makes it easy to produce green water, resulting in serious damage to the superstructure. However, the harsh environment numerical studies supported by experimental data on the bow configuration of tumblehome vessels are few. Based on the Cartesian Grid Finite Difference Method (CGFDM), this paper studied the motion response of the ship and the green water characteristics in regular waves under different bow configurations. The Finite Difference Method (FDM) based on a fixed regular staggered Cartesian grid system is used to solve the flow field, and the Tangent of Hyperbola for Interface Capturing with Slope Weighting (THINC/SW) scheme is used to capture the severe free surface flow. At the same time, the immersed boundary method is used to effectively solve the problem of the large motion of the object. The numerical simulation results were compared with the experimental values, showing good consistency. The calculation results show that the bow configuration has little effect on the motion response of the tumblehome vessel in regular waves and only shows some local differences in some wave conditions. Macroscopically, the change of stem angle has little effect on the green water degree of the ship. However, under high wave conditions, the change of stem angle greatly influences the height of green water and the slamming pressure characteristics of the ship. Compared with the bow configuration schemes with stem angles of 30° and 60°, the ship with the stem angle of 45° has a better comprehensive load performance when green water occurs. This study can provide a suitable reference for selecting ship types and structural designs of tumblehome vessels.

Design of Dihedral Bows: A New Type of Developable Added Bulbous Bows—Experimental Results

This paper presents the design and the experimental results of a new type of developable added bulbous bow that has been designated as a dihedral bow. This type of bow is based on polyhedral bows that are used in small vessels, whose origin is traced to the 1990s. The bow is designed with a set of developable surfaces that are designed following previous methodology on surface design that considers material properties and can contain boundary curves. Two dihedral bow designs and their towing tank tests are presented in this work. A displacement and a semi-displacement hull were tested in two different loading conditions and for different Froude numbers. An important reduction of the effective power (PE) of the ships with the dihedral bow was observed during the experiments. There is a reduction of about 20% for the displacement hull and about 16% for the semi-displacement. The design methodology for the dihedral bows is presented in this paper together with experimental results on power, sink and trim. Dihedral bows are a good option for efficient small ship design, as well as larger ships.

Comparative Study of Ship Resistance and Fuel Consumption between Axe Bow and Moor Deep Ram Bow using CFD Method

Using a bulbous bow on the ship is the most common alternative way used to reduce resistance and fuel consumption. Some developments are created in terms of bow shapes to obtain the minimum shipping cost. The purpose of this study is to compare the total resistance (Rt) and specific fuel oil consumption (SFOC) in an 8000 DWT oil tanker by modifying the existing moor deep ram bow to axe bow using computational fluid dynamics (CFD) and empirical Holtrop method. Based on the results, the total resistance with a moor deep ram bow design at a service speed of 12 knots is 230,8 kN, while axe bow is 221,5 kN. This is directly proportional to the fuel consumption where by using axe bow, the ship will consume 83.64 tons in a trip of 1912 nautical miles. In contrast, with existing moor deep ram bow, the fuel consumption is just a slight 0.1 % higher than axe bow and still showing a competitive performance as it is generally used in cargo vessel.

Preliminary Bulbous Bow Design Tool Applying K Nearest Neighbours Classification and Regression Model

Designing bulbous bows for ships remains a challenging task. Their impact on different design attributes as well as their change in performance when operating off their intended design condition renders this as a multidimensional problem. This paper explores the application of machine learning techniques to a sample of in-service vessel data to develop a preliminary design tool. The ships' data was analysed together with their bulbous bow data to generate machine learning models using a supervised approach. The K Nearest Neighbours Classifier and Regression models were used as the basis of the tool. Together, these models can be used to predict whether to install a bulbous bow and the recommended dimensionless coefficients for new vessels. Generating this preliminary bulbous bow design tool required the introduction of new dimensionless coefficients that discretise the bulbous bow's longitudinal section. The preliminary design tool gives the designer the ability to determine whether a bulbous bow should be fitted and, if so, to obtain an initial estimate of the bulbous bow required for the vessel being designed, based on key input parameters that relate to the ship and its operation. The new design tool is demonstrated to provide preliminary design details for bulbous bows through the case studies.

Cultural evolution: Is causal inference the secret of our success?

A new study investigates hunters' causal understandings of bow design and mechanics among the Hadza, one of the last remaining foraging populations. The results suggest that sophisticated technology can evolve without complete causal understanding.

Optimal design method of bulbous bow for fishing vessels

Although widely used, the design of the bulbous bow for ships has been difficult due to the complex interference between the wave system generated by the bulb and the wave system of the ship hull. Until now, a bulbous bow has been often designed using Kracht charts, which were established based on model test data, but these charts apply only to ships with a block coefficient C B = 0.56-0.82, Froude number Fn = 0.20-0.40, and the obtained bulb sizes are only close to optimal. This paper presents a new method for the optimal design of bulbous bow, starting from the design of an initial bulb using Kracht charts for ships with any block coefficient or Froude number, then resizing this initial bulb to define the optimal bulb sizes based on a multi-objective function of the required power reduction, and a combined solution of Computation Fluid Dynamics (CFD) analysis and surrogate models. This study was applied to a fishing vessel FAO 75, which has been model tested and used to design steel fishing vessels in Vietnam recently. The obtained quantitative results showed the same trend as the theory and practice, with a reduction of the ship’s required power by about 14%.

Redesign KCR 60m Bow with Axe Bow Type To Reduce Ship Resistance

Indonesian Navy continues to build 60 Meter Fast Missile Boat (KCR-60) is one of them and acts as a fast patrol boat and high-speed combatant ship in the archipelago warfare. The bow of the ship is an important part in the design of the ship as well as the bow of the KCR-60, because it is the most stressed, stressed from the waves, with the bow design that has a bow profile like an axe, the slender shape of the waterline is able to reduce the impact waves, increase the efficiency of the inflow rate, reduce the resistance of the vessel received so increase a better speed. This study changed the design of the Conventional Bow KCR-60 into the Axe Bow design concept with numerically calculated the total resistance of the Bow Bow design using the Holtrop method and performed a comparative analysis with the computing program MARIN DESPPC 1999 and Maxsurf Resistance V8i software. The results of this study found the total resistance value of KCR-60 Axe Bow type at 28 Knots speed was 364.2 KN and Conventional Bow type was 374.5 KN, the difference was 10.3 kN or 2.75% smaller than the Conventional Bow type in the analysis comparison of Maxsurf Resistance V8i software. For comparative analysis of the MARIN DESPPC 1999 program the total resistance value of the KCR-60 Axe Bow concept at 28 Knots is 283.6 KN and the Conventional Bow type is 288.1 KN, the difference is 4.5 KN 1.56% smaller than the Conventional type.

The static deformation of the asymmetric Japanese bow: modelling bow asymmetries with the elastica theory

The static deformation of symmetric bow limbs has been widely studied in the last century. However, asymmetries in shape and length which correspond to a more realistic situation, have not been thoroughly investigated. Here, we report a model for asymmetric bows based on the elastica theory and solved numerically by the Runge–Kutta method. We apply the model to describe the large asymmetric deformation which occurs in the Japanese bow, currently employed in the Japanese martial art of Kyūdō. We compare the model with experimental data acquired from a modern glass-fiber bow and a traditional bamboo bow, different in shape and construction. The model provides accurate results in predicting the deformation and the total energy stored in the bows, as long as the bending stiffness of the limbs is correctly reproduced. The energy is reproduced with an error within 1% and the unbraced and drawn shapes are reproduced with an RMSE of few millimeters compared to the length of $$\sim \,2.2\,\hbox {m}$$ of the bows. We investigate the influence of the grip position on the bow strength and shape which is not possible using classic symmetric models. At the end we show the possibility to analyze the bow design and potential failures by computing the bending stress extracted from the solution of the model. This study provides a further development with respect to the existing bow models by including the effect of the limb’s asymmetries in the static performances of the bows. The model for asymmetric limbs can bring important contributions for the design of the bows, reconstruction of ancient bows as well as to study the influence of the asymmetries on the targeting performance in modern competitive archery.

Archery Bow Design Equation

Bow and arrow is one of the ancient combat tool used for defense, hunting and in recent times, used in sports. There have been several improvements in archery since then. Bows, as we know today are made from several components, materials and are available in different shapes and designs. There have been several variations in the bow design, broadly categorized under traditional bow or long bow, recurve bow, cross bow and compound bow. They may look very different and may have different efficiency but their underlying principle of operations have not changed much in past decades. There have been several studies and patents filed for new designs of the bows to improve the efficiency and several accessories have also been introduced to improve targeting, stability, and power. In this study using laws of physics, a design equation has been established which can be used as basis for deriving various aspects of the bow design and can be used for creating new bow designs with added efficiency. The bow design equation in this study is named as ‘RV bow design equation’ which is split into three parts to cover the aspect of arrow mass, energy stored in the bow, and energy transferred to arrow to give designers holistic view of the bow design and ability to monitor several parameters independently and in conjunction to each other. This equation will facilitate designers to make informed decisions about several aspects of the bow and they can use this equation to maximize the energy or velocity output of the arrow with a given design and material used for construction.

Archery Bow Design Equation

Bow and arrow is one of the ancient combat tool used for defense, hunting and in recent times, used in sports. There have been several improvements in archery since then. Bows, as we know today are made from several components, materials and are available in different shapes and designs. There have been several variations in the bow design, broadly categorized under traditional bow or long bow, recurve bow, cross bow and compound bow. They may look very different and may have different efficiency but their underlying principle of operations have not changed much in past decades. There have been several studies and patents filed for new designs of the bows to improve the efficiency and several accessories have also been introduced to improve targeting, stability, and power. In this study using laws of physics, a design equation has been established which can be used as basis for deriving various aspects of the bow design and can be used for creating new bow designs with added efficiency. The bow design equation in this study is named as ‘RV bow design equation’ which is split into three parts to cover the aspect of arrow mass, energy stored in the bow, and energy transferred to arrow to give designers holistic view of the bow design and ability to monitor several parameters independently and in conjunction to each other. This equation will facilitate designers to make informed decisions about several aspects of the bow and they can use this equation to maximize the energy or velocity output of the arrow with a given design and material used for construction.

NUMERICAL INVESTIGATION OF THE EFFECT ON FOUR BOW DESIGNS FLAT HULL SHIP

Flat hull ship has some advantages in the manufacturing aspect which are relatively easy to fabricate and does not require high technology equipment. This ship has a weakness where the resistance of flat hull ship is bigger than the other ships among streamlined bow. A factor that influences the ship resistance is the type of bow. So, this study is needed to investigate the effects of bow design and ship resistance. This study aims to reveal the influence of various bows design on resistance and speed of flat hull ship. This study method is numerical analysis using Maxsurf software. The analysis was carried out on four types of bow direction for flat plate hull types, namely Raked Bow, Maier Form, Raked Bow II, and Plumb Bow. The result shows that the flat hull ship with the Raked Bow had the lowest resistance and power. Meanwhile, the flat hull ship with raked bow II had the highest resistance. These results can be a guide for the shipping industry on development and production, and for other researchers in developing the flat hull ship

Application of the Design of Experiments and Computational Fluid Dynamics to Bow Design Improvement

Techniques of the design of experiments (DOE) and computational fluid dynamics (CFD) were applied for improving the bow shape of a tanker hull. Through this, a hull that could reduce the added resistance in waves was derived. The key design elements of the bow shape were selected as parameters for design optimization and added resistance in the short-wavelength region was interpreted through CFD considering the operational condition of the full scale ship. For design parameter changes, the number of analyses was minimized by applying DOE. The regression equation for calculating added resistance was derived using bow-shape design parameters by applying the response surface method and regression analysis to obtain the optimal hull with minimal added resistance was derived. The methodology was applied to an Aframax tanker hull form, and the derived added resistance regression equation and the added resistance value obtained through CFD analysis showed a difference of approximately 1%. The model test results of the improved hull form showed that the added resistance was reduced by 52% in comparison to that obtained for the original hull form.

Experimental testing and simulations of an autonomous, self-propulsion and self-measuring tanker ship model

Improving the energy efficiency of ships has generated significant research interest due to the need to reduce operational costs and mitigate negative environmental impacts. Numerous hydrodynamic energy saving technologies have been proposed. Their overall performance needs to be assessed prior to implementation. A new approach to this evaluation is investigated at model scale which applies an approach comparable to that applied for the performance monitoring of a full scale ship. That is long duration testing that measures power consumption for given environmental and ship operating conditions and can use statistical analysis of the resultant large amount of data to identify performance gains. As a demonstration of the approach, an autonomous, self-propelled and self-measuring free running ship model of an Ice Class tanker is developed. A series of lake based and towing tank tests experiments have been conducted which included bollard pull, shaft efficiency, naked-hull, self-propulsion, and manoeuvrability tests. These investigated the efficiency improvement resulting from changing the ship operational trim and testing different bow designs. An associated mathematical model for the time domain simulation of the autonomous ship model provides an effective tool for data analysis. It has been demonstrated that the use of a suitably instrumented self-propelled autonomous ship model can provide long duration tests that incorporates the influence of varying environmental conditions and thereby identify marginal gains in ship energy efficiency.