Hull Shape Research Articles

Hull Form Factor Prediction of Mini Submarine Model Using Prohaska Method

Speaking of prisoners on mini-submarines is certainly different Fnom the type of surface vessels in general. This is related to differences in the shape of the sub's hull when compared to surface ship. In addition to differences in the shape of the hull, the difference in the operational area of ​​the ship is also different, where the submarine's hull operates at full water depth, while the surface ship the ship hull partly operates at sea level. If the submarine model is tested then the value of the coefficient of resistance will be very different. Where the component of the coefficient of resistance (CT) consists of the coefficient of Fniction (CF), form factor (1+K), and Correlate Allowance (CA). Because the hull shape is different Fnom the surface ship, then the hull form factor coefficient is the focus of this study. The prediction of the hull form factor can be searched using the PROHASKA method. Where this method is done using a mini-submarine model test. By the known value of the hull form factor, then it can be used to find the value of the coefficient of resistance and can know the resistance of the ship

Analysis of the effect of addition of stern flaps on the performance of 60 m fast boat

Regulations from the International Maritime Organization (IMO) regarding energy efficiency mean that the ship design must have the least possible resistance so that fuel consumption is also low. Several modifications to the shape of the hull have been developed so that the performance of the ship can be improved so that its use is more efficient. The stern flap is a modification of the hull shape by adding an appendage to the lower transom. The application of the use of a stern flap can improve the movement of ships that are too heavy behind, causing the ship to have a tendency to trim the stern, increasing hydrodynamic work and reducing the obstacles that work while the ship is operating. This study analyzes the effect of adding an appendage to the stern in the form of a stern flap on the performance of fast boats using a computer program based on Computation Fluid Dynamic (CFD). This study was conducted by comparing the results of the analysis of the original model, namely without adding flaps with variations in the addition of flaps at the stern of the ship. Based on the analysis results, obtained an increase in ship performance for each stern flap variation compared to the original model. Flap V model with a flap length of 2% LPP and a Trailling Edge Down (TED) angle of 90 is the best variation. The total resistance value at each speed has a better decrease. Compared to other models, the total resistance of the ship is reduced by 5.53%.

Investigating the Performance of a Ship by Matching the Stern Hull Form to Propeller and Engine Power

Designing the form of the ship stern hull could have some impacts on the efficiency of ship propeller and the requirement of the ship speed. Therefore, stern hull form of a ship matched to its propeller and engine power is important consideration in preliminary ship design stage. The main objective of this study is to investigate ship performance by matching the stern hull shape to the propeller diameter and engine power toward high speed. This study was conducted by free running model test and Maxsurf Resistance application. The stern forms were employed U-shape and V-shape. In addition, the fixed pitch propeller (FPP) with three blades was used and the diameter is varied into three sizes 0.032 m, 0.040 m, and 0.048 m. The results show the increase of propeller diameter increases model’s speed for both U-shape and V-shape stern and the effect of the propeller diameter on the speed could be described by using the equations of second-order polynomial. The optimum propeller diameter could be determined taking into account stern hull form, stern shape, tip clearance, and proper speed where then propeller diameter related to draft is given by 0.79T with tip clearance 10%Dp for both U-shape and V-shape. The ship resistances of U-shape stern at Fr 0.221 and V-shape at 0.208 are obtained approximately 89.797 KN and 77.10 KN respectively. Furthermore, the powers of ship for both U-shape and V-shape at those Fr are obtained 904,374 KW and 726,807 KW respectively. Finally, the best stern hull form matched to propeller diameter and engine power is selected and given by U-shape stern.

Design and optimization of a bio-inspired hull shape for AUV by surrogate model technology

This paper proposes a bio-inspired hull shape (BHS) for AUV by studying and modeling the body shape of humpback whales. Among factors affecting hydrodynamic characteristics, this paper considers both the hull drag and displacement volume to optimize the BHS, which profitably improve the space utilization and voyage of the AUV. The optimization is conducted by a surrogate model using response surface methodology (RSM), during which the translational propagation Latin hypercube design (TPLHD) is adopted to obtain sampling points. In order to verify the optimization results of BHS, the drag computations for BHS and eight typical hull shapes of existing typical or bionic AUVs are performed for comparison under conditions of similar volume, wet surface area, body length and attachments. A scaled-down model of BHS with attachments is then designed, manufactured and carried out a towing tank test. The drag measured in the towing tank test is basically the same as the simulation result, with the average relative error of 3.68% at 4m/s. The result of the shape optimization performed with the RSM is effective. Furthermore, the proposed BHS is highly suitable for underwater vehicles with requirements for longer distance, higher speed or better sensor carrying capacity.

Hydrodynamic Analysis in Redesigning a Monohull Passenger Ship into a Catamaran

In line with technological developments, many studies have led to the factors that consider hull shape planning. Therefore, innovations in hull form planning are the primary basis for obtaining a hull that is considered efficient in reducing ship resistance and fuel consumption. This study aims to modify the design of a monohull and transform it into a catamaran while maintaining the total length and Displacement ratio. The ship model used is the Monohull passenger ship with a rounded shape and modified to become a catamaran with a chine shape. The hull chine symmetrical was determined by stagger to the length ratio of S/L 0.3. The hydrodynamic investigations and calculations of models using Computational Fluid Dynamic (CFD). Analysis hydrodynamic on both hulls carried out on the components of total resistance, viscous resistance, friction resistance, and wave resistance with variations of Froude number: 0.3: 0.5: 0.7: 0.9 and 1.2. From the results of the analysis, it is found that the calculation of the coefficient of resistance on the catamaran with the Chine hull is smaller than the monohull. Fn 0.7 at S/L 0.3, the catamaran produces a resistance coefficient that is more favorable than the other speeds.

«Руский тип» подводных лодок: от «Дельфина» до «Барса»

The rise of submarine shipbuilding in Russia of 1900–1915 was influenced by the shortage of financial, technical and personnel resources. And yet the fleet received, along with American and German, boats of domestic design. Their design was concentrated in the hands of the outstanding theorist and engineer I.G. Bubnov, who announced the development of a special "Russian type" of a submarine that embodied the theoretical installations professed by him. The ships created according to Bubnov's designs are often regarded by fleet historians as unsurpassed in the world naval technology. Such a view contradicts the concrete data accumulated in historical research and needs critical consideration. For this purpose it is used classical methods of source studies and analysis of historiographical practice. The actual data indicate the harm brought to the fleet by the monopolization of scientific and technical activities. Submariners have developed a critical attitude towards the imposed type with its inherent number of persistent shortcomings. Bubnov refused to correct the shape of the hull which caused excessive water resistance. At the same time, in an effort to achieve the set speed of the boat, the designer envisaged in his projects such a powerful power plant that it exceeded the real capabilities of mechanical engineering and was also heavy and cumbersome. The boat commanders and engineers pointed out the need to reduce the submerging time of the boats, increase their survivability, add watertight bulkheads, abandon the low-impact mine vehicles of Dzhevetsky system, make the hull shape more streamlined, but the maritime administration preferred to save time and money and dismissed claims, sacrificing the comfort and safety of the crews. The experience of the First World War and familiarization with the most successful American and British designs nevertheless prompted I.G. Bubnov in 1915-1916. to revise the design principles concerning the shape of the hull, the internal structure of boats, the nature of engines, weapons, but the more advanced projects prepared by him could not be realized.

Анализ особенностей формы корпуса традиционных и современных ледоколов

This paper discusses hull shapes of conventional and modern icebreakers to analyse the peculiarities of their bows, sterns and parallel midbodies. It discusses main performance parameters, main dimensions and hull shape details of conventional and modern icebreakers. The data base generated in this study includes hull shape details for bow, parallel midbody and stern ice belt areas of conventional and modern icebreakers. This work also yielded mean statistical data making it possible to judge how waterline slope and side slope depend on the position of design section. This study summarizes and generalizes overall design data for the majority of icebreakers operating in freezing Russian waters, including the Arctic. Depending on hull shape, displacement and ice class, this paper identifies three representative groups of icebreakers. The results of this study were further used to analyse the loads on ice belt structures of icebreakers, as well as to develop a system of relationships intended to obtain design ice loads as per RS Rules.

Применение поисковых методов для обоснования усилений конструкций ледового пояса при переходе иностранных судов ледового плавания в класс российского морского регистра судоходства

This paper discusses a multifunctional vessel (displacement 10406 t) with ice class IA Super assigned upon construction. This ice class is a part of classification for Baltic ice-going ships. The purpose of this study is to justify the variant of upgrading the ice belt of this vessel by strengthening its current framing by means of additional welded elements. The paper analyses main characteristics and particulars of this ship, as well as its hull shape parameters. Possible structural upgrades are justified through solution of an optimization search problem by means of mathematical programming and finiteelement method.

Experimental and Numerical Investigation of Green Water Occurrence for KRISO Container Ship

The occurrence of green water on the deck of Korea Research Institute of Ships & Ocean Engineering (KRISO) container ship is investigated using model test experiments and a fully coupled impulse response function (IRF)–computational fluid dynamics (CFD)–based numerical approach. In the experimental study, green water pressure over the deck and superstructure is investigated for different regular head wave conditions (wavelength/ship length ratio: .8–1.5) and vessel speeds (Froude number: .055–.166). The impact pressure on the deck is found to be highest at a wavelength/ ship length ratio of 1.2 and increases drastically with the increase in Froude number. The variation of green water pressure with wave steepness is linear for points on the forward deck and quadratic for the superstructure. In the second part, a coupled IRF-CFD–based numerical method is developed in which the global hydrodynamic forces such as radiation–diffraction and Froude–Krylov force are computed using a potential flow solver, whereas the local pressure due to the shipping water impact is computed using CFD and added as an external force. Comparisons of vessel motions and green water pressures with experiments indicate that the coupled IRF-CFD method can be a robust and efficient tool to predict shipping water loads on ships. Introduction The prediction of green water shipped on the deck and the resulting impact on ships and offshore structures have been an important research topic in the last couple of decades because it is directly related to the safety of the structure at sea. Historically, shipping of water on the deck had caused many serious damages to the bow and superstructure, and some of them have even capsized; e.g., the Schiehallion Floating Production Storage and Offloading (FPSO) was damaged severely in November 1998 because of steep waves. These incidents resulted in considerable research on this topic in the past two decades. The primary focus has been on the understanding of critical aspects and the accurate prediction of green water loading which requires proper modeling of green water occurrence. Also, accurate calculation of the green water loads on the deck and superstructure is very important for structural design load calculation. However, this is a nontrivial task because it depends on many physical and geometrical factors such as wave steepness, the wavelength- to-ship length ratio, hull shape around the bow region, and vessel speed. Hence, efforts have been made to develop suitable numerical models that may consider most of these aspects under necessary underlying assumptions.

Determination of Seakeeping Performance for a Case Study Vessel by the Strip Theory Method

Abstract The increase of seakeeping performance is of particular importance for car and passenger ferries, service ships in the gas and oil extraction industry and offshore wind power farm industry, as well as for special purpose ships (including military applications). In the water areas of the Baltic Sea, North Sea, and Mediterranean Sea, which are characterised by a short and steep wave, the hull shape has a substantial impact on the operational capacity and propulsion efficiency of the ship, as well as on comfort and safety of navigation. The article analyses selected aspects of seakeeping for four variants of a selected case study vessel, indicating practical limitations of the strip method. The analysed aspects included hull heaving and pitching, added resistance, Motion Thickness Indicator (MSI), and Subjective Magnitude (SM). Experimental tests were also performed in the towing tank. Their comparison with the numerical results has indicated high inaccuracy of the strip method. What is more, the simplified representation of hull shape used in the strip method makes it impossible to analyse the effect of hull shape changes on the predicted seakeeping characteristics. Especially for the case of head wave, neglecting highly non-linear phenomena, such as slamming or head wave breaking, in strip method-based computer simulations will significantly decrease the reliability of the obtained results. When using the strip method, the seakeeping analysis should be complemented with model tests in a towing tank, or by another more complex numerical analysis, such as CFD for instance.

Numerical Prediction of Hydrodynamic Performance of Planing Trimaran with a Wave-Piercing Bow

The central hull is the most important structure in the planing trimaran. In order to gain insight into the relationship between hydrodynamic performance and main hull shape, experimental tests and numerical simulations were carried out for volume Froude Number (FrΔ) ranging from 1.31 to 4.98. Dynamic sinkage and trim in the Dynamic Fluid Body Interaction (DFBI) six-degree-of-freedom model were considered. A validation study carried out by comparison of experimental test results with numerical results showed good consistency. To analyze the process of tunnel penetration and pressure change at the bottom of the boat, numerical simulation results for free surface, bottom streamline, and pressure distribution around the hull are given. A large triangular high-pressure area was observed in the front of the main hull for all volume Froude numbers. Consequently, the central drainage body, in reference to the profile of single planing craft with distinctive resistance performance, was redesigned into a wave-piercing shape. Total resistance, sinkage, and trim angle of the new model were then predicted by numerical method. The results show that the central drainage body has a significant impact on the hydrodynamic performance of the planing trimaran. Furthermore, the wave-piercing shaped main hull has a drag reduction effect.

Vertical Motion Optimization of Series 60 Hull Forms Using Response Surface Methods

There are many aspects to analyze seakeeping performance, one of which is the ship's vertical motion. As well-known, vertical motion and its derivatives, vertical velocity and acceleration, will be related to other aspects of seakeeping performance, such as slamming, deck wetness, and MSI. This study discusses optimizing the hull shape with small vertical motion using the Response Surface Methods (RSM). This research aims to minimize the ship's vertical motion so that the ship's performance is better than the initial one. Besides, this research was conducted to apply the RSM in the naval architecture field. The hull's shape used in this study is Series 60 hull form with a length of 31 m. The variables used for the optimization process are the ratio of L/B (X1) and B/T (X2) in the range of ± 10% with fixed displacement. Seakeeping analysis was carried out at a speed of 6.78 knots (Fr 0.2), a heading angle of 180°, and a significant wave height of 0.77 meters. The results show that the optimum model is found in Model 9 where the value of X1 = -2.94 or L/B = 6.71 and X2 = 5 or B/T = 2.75. Model 9 can reduce the vertical motion of the ship by 16.38%.

Parametric hull shape variations by Reduced Order Model based geometric transformation

The representation and the variation of hull shapes are two challenging problems in naval architecture due to the complexity of the geometry and to the need to ensure the fairness of the surfaces. Conventional CAD techniques are widely used to accurately describe the hull shape. However, they are rather complex to be easily used to generate hull shape variations due to the great number of variables involved. We propose a study to highlight the pro and cons of the application of space reduction techniques, usually referred to as Reduced Order Models (ROMs), to create a parametric model for both global and local hull shape variations. A geometric transformation relying on the Proper Orthogonal Decomposition (POD) method is applied on top of a combined subdivision surface — Free Form Deformation (FFD) approach conceived for modeling and variation of hull shapes. The analysis focuses on highlighting the geometric meaning of the new POD basis functions and on how this model affects the variability of the explored design space. Two studies are developed in order to show possible applications of this technique. In the first one a new set of selection criteria for the POD modes based on geometric considerations are proposed to use it on uncorrelated geometric domains. In the latter the large-dimensional space of the so-called Design Velocities (DV), related to the shape sensitivity, is reduced by using the POD approach to create a new transformation of the hull shape.

Evolution of the Tension Leg Platform

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30752, “The Tension Leg Platform: From Hutton to Big Foot,” by Steven J. Leverette, Leverette Offshore, and Stephen B. Hodges, Shell (Retired), prepared for the 2020 Offshore Technology Conference, originally scheduled to be held in Houston, 4-7 May. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. The complete paper is a comprehensive discussion of the development and deployment of the tension leg platform (TLP), one of the four major platform types that also include floating production, storage, and offloading (FPSO) vessels; semisubmersible floating production systems; and spar platforms. The authors summarize the evolution of the TLP during a nearly 4-decade span and provide a retrospective of the progression of TLP technology, including hull shapes, tendon connectors, flex elements, and riser systems. A Design Driven by Function Although the technology involved may be impressive, the authors remind that essentially it is merely a means of supporting a payload economically in deep water within required motion limits. The ultimate objective is to provide the most cost-effective, safe, reliable platform to meet functional requirements. After almost 50 years of deep water development, platform concepts have broadly stabilized into four categories of functionality: semisubmersibles, TLPs, spars, and ship-shaped FPSOs. Each of these concepts brings unique functionality with different cost/benefit tradeoffs. The driver behind the TLP concept was straightforward from an operator’s perspective: Provide a platform that behaves like a fixed platform with regard to the wells (i.e., dry trees; direct vertical access to wells; minimal tensioner stroke, allowing an array of wells in close proximity without giant tensioner systems such as those found on drilling semisubmersibles; and enabling export risers) in water depths much deeper than any fixed platform. This functionality, however, comes at a cost. While a semisubmersible may look similar in terms of hull and topsides, a TLP designed for the same payload requires 10 to 30% more displacement to provide the pretension in the tendons that keeps them in tension even in the most severe environmental conditions. The TLP also features 10 to 30% more freeboard to account for set-down at large offsets. While a semisubmersible, spar, or FPSO rides the tide and waves, a TLP acts like a fixed structure and, furthermore, is pulled down in the water geometrically at offset positions. The cost of this phenomenon must be offset by improved functionality. Thus, a large TLP with a full drilling rig and 24 wells can be an excellent choice for a large, centralized reservoir that can be drilled from a single location, but it makes little sense in developing a group of small reservoirs spread out over a region.

Comparison of propeller thrust based on the purse seiner body shape

The engine on a fishing vessel is the main equipment that is assembled in a vessel’s machining system. The vessel’s engine, as the main driving force, is coupled with a propeller, which functions to provide thrust to the vessel. The efficiency and effectiveness of the propeller used on fishing vessels depend on the dimensions of the propeller and the type of fishing gear used, as well as the shape and size of the hull. The correlation between vessels, engines, and propellers in vessel planning determines the successful fishing operation. The objective of this study was to examine the geometrical relationship of the purse seine hull to the effectiveness and efficiency of the propeller. The analysis was conducted on nine samples of purse seiner operating in the Flores Sea through numerical simulations. The sample vessel designs were drawn from the vessel offset data using the max surf software to obtain the shape of the hull. Furthermore, the vessel shape specifications were simulated with the propeller technical specifications to obtain propeller efficiency values based on the shape of the hull. The results showed that the pressure value on the propeller used on purse seiners with round bottom was lower than the pressure experienced by the propeller on a U-bottom. Propeller efficiency values were higher on round bottom purse seiners than U-bottom forms. This value illustrates that the propeller thrust was greater in round-bottom vessels. This is probably indicated that the value of resistance on the U-bottom hull form was greater than the round bottom hull shape.

Fish-like shaped robot for underwater surveillance and reconnaissance – Hull design and study of drag and noise

Undulating propulsion is promising solution for underwater vehicles used in subsea security systems, especially due to its low noise, better energetic efficiency, low water turbulence and living animals mimicry. The design of the biomimetic autonomous underwater vehicle (BAUV) for intelligence surveillance and reconnaissance (ISR), built in the SABUVIS project, is presented in the paper. The shape of the vehicle hull was inspired by living fish. Key aspects of the design and construction of BAUV needed to achieve tasks required to be performed by the robot are described. Two research questions are stated in the paper: how big drag forces act on a biomimetic underwater vehicle and how mechanical design influences the noise level generated by the vehicle. To answer these questions vehicle forward velocity, hull drag, added mass and generated noise were investigated. Forces acting on the BAUV hull while being pulled forward and sideways were measured. Noise generated by the vehicle was also measured for two types of propulsors’ drives in order to select those with the lower sound pressure level. Quantitative results of drag and noise obtained in the research are important for designers of mechanical structures of useful, full scale biomimetic underwater robots and their control subsystems.

Numerical Study of Pre-Duct on Traditional Fishing Vessels as Energy Saving Device (ESD)

This paper is aimed to investigate the effect of Energy Saving Device (ESD), namely Pre-Duct on traditional fishing vessels, in improving ship propulsor performance thus increase energy efficiency. Traditional fishing vessel in Lamongan coast are fishing vessels built by local shipbuilders based on experience and shipbuilder instincts from ancestors not based on the design of vessels, hull shape parametric of vessel is : L/∇1/3=3.97; L/B=3.06; Cb=0.49; Cm=0.73; Cw=0.78; Cp=0.7 and principal particulars of traditional fishing vessel is : Loa=9.5 m; Bmld=3.10 m; H=1.2 m; T=0.95 m. Simulation study on traditional fishing vessels was conducted using CFD approach together with the use of CFX commercial code; the simulation results determined the thrust and propulsive coefficient of vessels with and without pre-duct. Based on systematic comparisons of pre-duct and without pre-duct on traditional fishing vessels, the implementation of pre-duct has increased efficiency of energy and improving ship propulsor performance about 3%.

Mapping and spatial statistical analysis of Mars Yardangs

Mars yardang fields were mapped using the newly available high-resolution Context Camera (CTX) mosaics (30°N to 30°S) through visual interpretation and manual digitization. We classified the Martian yardangs into three types according to their shapes: long ridge, inverted hull and curvilinear shapes, and found that the number of long ridge yardang fields account for 77.97% of all 394 yardang fields. The mapping results show that the total area of yardang fields is about 734,115 km2, within which the area of the Medusae Fossae Formation (MFF) yardangs is about 562,640 km2. We also identified and digitized individual yardang bodies wider than 500 m in the CTX mosaics. The resultant 466 yardang bodies are subsequently used as samples for statistical analysis of the morphometric parameters. Among all of the orientations, N–S is the dominant orientation of the yardang samples, and the average length and width are 5626 m and 993 m respectively. The length to width ratios vary from 1.2:1 to 46.9:1 within (30°N to 30°S) and vary from 1.5:1 to 46.9:1 in the most studied MFF. The mapping and statistical results provide important information about the spatial distribution of Mars yardangs and their morphological characteristics, which will be valuable to further study of the formation and evolution of Mars yardangs, and the aeolian environment.

Glider performance analysis and intermediate-fidelity modelling of underwater vehicles

This paper analyses the transit performance of state-of-the-art underwater vehicles and presents an intermediate-fidelity steady-state flight mechanics model for qualitative performance assessment of underwater vehicles. Focusing on the comparison of underwater gliders and propeller-driven AUVs, a simple glide metric is presented and the transit performance of the legacy underwater gliders Slocum, Spray and Seaglider as well as propeller-modified versions thereof is evaluated. The evaluation is based on various data sets from wind tunnel tests and Computational Fluid Dynamics (CFD) studies, and shows that for the respective hull shapes gliding locomotion proves more efficient in ideal conditions. However, biofouling conditions inflict a double penalty on glider performance, rendering gliders inferior to propeller-driven vehicles. The Slocum data set is used to validate a steady-state flight mechanics model for qualitative performance prediction. It is shown that even simplistic models based on semi-empirical and analytical expressions can be successfully used for design optimization through parametrization. Being computationally efficient, the model can be a useful tool for design engineers in early design phases. The model is used to evaluate the effects of wing span on gliding efficiency, indicating that the current design of the Slocum glider is near-optimal.

Principles of the tugboats’ surface systematization in the development of theoretical drawing by the interpolation method

The work is devoted to the issues of the tugboat’s surface development by the interpolation method at the early design stages. The developed theoretical drawing of the tugboat’s hull should correspond as much as possible to the specified parameters, namely, the calculated values ​​of the overall completeness ratio and the relative abscissa of the magnitude center. The principles of the approach to existing ship hulls’ systematization are given and the possibility of their application for developing a theoretical surface with the specified parameters is evaluated. As a result of the analysis, systematization and selection of the most suitable hulls for processing were carried out. The variety of hull shapes has been successfully brought to a single system, which is necessary for interpolation, and consequently for creation of a new hull with the specified parameters. The adopted approach to the ship surface development can be used to automate the process of obtaining it.