Ship Theory Research Articles

Study on the design method of an automatic outrigger layout control system for variable outrigger layout trimaran

During the navigation of a trimaran, its wave resistance is influenced by both sailing speed and outrigger layout. In the case of a variable outrigger layout trimaran, due to the adjustability of its outrigger layout according to different speeds, its wave resistance will be lower than that of traditional trimarans. In this paper, an automatic outrigger layout control system is figured out for a variable outrigger layout trimaran. The system can control and regulate the position of outriggers according to the traveling speed in order to reduce the wave resistance during navigation. The slender ship theory based resistance calculation program is applied as the solver in this system to evaluate the wave resistance of the trimaran and further determine the optimal outrigger layout under a specific speed. In order to improve the calculation accuracy, NURBS (Non-Uniform Rational B-Splines) method is introduced to modeling the hull surface. Model tests for trimaran with 6 different outrigger layouts are conducted to obtain the resistance of the trimaran in order to validate the numerical method. The steepest descent method is applied to solve the problem of searching the outrigger layout with minimum wave resistance efficiently. On this basis, an open-loop control system for trimaran outrigger layout is designed based on PID (Proportional Integral Derivative) algorithm with the control objective derived by the solver. Finally, a outrigger layout adjustment simulation (when speed changes from Fr=0.4 to Fr=0.35) is conducted on the experimental trimaran model. By comparing the resistance results obtained by numerical method utilized in this paper to the results obtained by CFD (Computational Fluid Dynamics) simulations, the effectiveness of the proposed system is validated.

Diversity, quality, and quantity of real ship data on the black-box and gray-box prediction models of ship fuel consumption

Establishing an efficient and reliable fuel consumption prediction model by using big data from ships facilitates optimized decision-making and ensures the green and intelligent development of ships. As data are crucial in model construction, this study presents a general multi-source data processing method for obtaining high-quality training data. A long short-term memory (LSTM) neural network, suitable for time-series data, was used to develop the fuel consumption black-box model. This was combined with the ship theory to establish a fuel consumption theoretical model, thereby generating the LSTM based gray-box model. We explored the impact of data diversity, quality, and quantity on black-box and gray-box models. Analysis of the navigation data of a passenger ship and meteorological data collected from the European Centre for Medium-Range Weather Forecasts (ECMWF) and MeteoBlue indicated that the combination of variables obtained via the feature selection of the least absolute shrinkage and selection operator (LASSO) statistical method yielded the best overall prediction performance. Moreover, the gray-box model was relatively stable in terms of the changes in effective variables. An analysis of data quality revealed that the systematic processing of outliers, which improves the accuracy of both models by 6.19% compared with direct deletion. Furthermore, the gray-box models use less amounts of data than the black-box models to achieve higher accuracy.

Совершенствование геометрических характеристик водометного движителя насосного типа для судов и кораблей

Object and purpose of research. This paper discusses pump jet propulsor. The purpose of the study was to improve its elements through experimental and theoretical investigation of its hydrodynamics and cavitation properties. This work is a part of the project intended to develop an application for a useful model. Subject matter and methods. To achieve its purposes, the work follows both theoretical and experimental research methods of ship theory. Numerical simulation of pump jet operation was performed in Siemens StarCCM+ commercial software package, and also as per in-house Krylov State Research Centre calculation methods for unviscous and viscous flows. Main results. The study suggests rotor and stator blade profiles that improve hydrodynamic and cavitation performance of basic pump jet versions. It also suggests updated shapes for pump jet stator and aft fairing. The study has shown that these improvements will increase the efficiency of pump jets by 3–5% as compared to the basic version, and will also eliminate several types of cavitation. Conclusion. The study was meant to improve pump jet elements so as to eliminate the flaws of the basic pump jet version. The results will be helpful in further pump jet design and development of the application for useful model.

Hull-shape parametric for minimising wave energy

This study presents a hull-ship parametric in reducing drag for minimising wave energy by comparing various numerical methods. The methods are Thin-ship theory, Rankine method, and Computational Fluid Dynamics (CFD). The methods are discussed in detail, with an emphasis on comparing wave and total drag as energy, wave profiles, and contours. The study results show that Rankine method entirely underpredicts the experimental results. Thin-ship theory cannot be adequately examined with a low Froude number, as evidenced by a test on total drag and calculation of wave energy. Although significant deviations exist, the CFD method provides a drag close to the experimental results. The Rankine approach displays a fairly apparent difference between the wave profile’s original hull of series 60 and the optimum parametric hull. Even if the wave’s profile line is identical to the profile from Rankine’s method, Thin-ship theory results do not sufficiently reveal the difference. From the testing results at Fr 0.24–0.32, the parametric optimal hull significantly reduced wave energy as wave drags by roughly 21%, Rankine by 17%, Thin ship theory by 7%, and CFD by 12.1%, respectively. Moreover, the wave contour of the methods illustrates a reasonably straightforward agreement. The outline of the wave at Fr 0.6 and 1.0 indicates that the optimum parametric hull’s wave contour shows that the wave’s spread is shorter, producing a lower drag.

Расчет эффективности преобразования энергии морского волнения в электроэнергию

Object and purpose of research. The object of the study is the wave energy converters (WEC) into electric power. The purpose of the study is to draw up a differential equation describing the operation of the WEC, its solution and determination for the design parameters influence of the WEC on the efficiency of energy conversion. Materials and methods. The theoretical methods adopted in ship mechanics and theory are used to study the operation of complex mechanisms and dynamics of marine objects. The data on the characteristics of electric generators are used. Main results. The differential equation describing the operation of the WEC on regular wave is compiled. The equation relates the characteristics of waves to the design parameters of the WEC. Generalized characteristics of electric generators are obtained. Systematic calculations are carried out; they show the influence of the WEC design parameters on the efficiency of wave energy conversion into electric power. Conclusion. The results can be used in design of the WEC. The resulting differential equation makes it possible to investigate the operation of the WEC in various marine conditions and to evaluate the influence of design parameters on the efficiency of energy conversion. The generalized characteristics of electric generators can be used in design of wave power structures and wind power plants.

Study on fast interference wave resistance optimization method for trimaran outrigger layout

The configuration of outriggers has a significant influence on the wave resistance of a trimaran. In this paper, slender ship theory is applied to calculate the wave resistance of trimarans. In order to improve the calculation accuracy, NURBS (Non-Uniform Rational B-Splines) method is introduced to molding the hull surface and the relative ideal results are obtained. On this basis, a series of 3D color maps of interference resistance (between main hull and outriggers) under different speeds and different displacement ratios are given to study the influence of the outrigger layout on the interference resistance. The results show that within an appropriate range, there is only one valley point of interference resistance exists in each 3D color map. For this reason, in combination with the characteristic of linear wave resistance has analytic expression, the steepest descent method can be applied to solve the problem of searching the outrigger layout with minimum wave resistance efficiently. Based on the above aspects, this paper proposes a fast trimaran outrigger layout resistance optimization method. By means of selecting an appropriate initial outrigger layout position, using trimaran wave resistance formula combined with steepest descent method, the minimum interference resistance layout in specific speed can be obtained efficiently. The results show a good precision of the optimal solution and an obvious promotion in computing efficiency compared to typical enumeration method.

Two-Analytical Comparison on Force Measurements and The Wave Pattern

This work presents a comparison of two analytical methods on the components of resistance, transverse and divergent waves, and the profile and contour of the waves. Michell’s thin linearization theory is applied to estimate the wave resistance and analysis of the method compared to the solution of the wave resistance coefficient based on the Rankine source method. The hull of series 60 is utilized as the initial hull, and varying the shape of the bow to the mid-ship with the hull offset variable. Computation of the wave resistance coefficient at low Froude number (Fr<0.3) shows the results of the wave resistance from the thin ship theory are higher, but it gives a graphical agreement with the Rankine source method. The wave profile provides a very similar profile line for both of them. However, the thin ship theory does not establish a significant difference in the wave profile from the initial hull of the improved hull variation. Comparison of contour displays is presented in different versions of the wave contour. Still, it affords a good contour match on the initial hull and the results of hull variations from both methods. At high Froude number (Fr>0.7), the initial hull and variations in the hull have minimal effects with small differences in wave resistance, profile and contour.

Method for optimization of design characteristics of high speed passenger catamarans

. In this paper we discuss the theoretical principles the method of design characteristics optimization of high-speed passenger catamarans. The goal of the paper is to determine the role and place of the proposed method in the development of sea passenger traffic and island tourism in the Socialist Republic of Vietnam and to illustrate its capabilities in relation to the interests of different participants of process. As a rule, the existing ships are purchased on the secondary market, and new ones are often designed and built at foreign shipyards. This is a reason to develop the design methods that take into account the regional characteristics of Vietnam. The novelty of this research is based on the fact that the proposed method takes into account the regional features, combines mathematical and optimization models of various design levels and allows to take into account the interests of participants of a program for development of maritime transport infrastructure and tourism in Vietnam. The theoretical principles of ship theory, ship design, mathematical programming and statistics were used for the method development.&#x0D; In this paper we present the results of design characteristics optimization of high-speed passenger catamarans and comparative analysis of these results with the main dimensions of modern high-speed passenger catamarans. The proposed method can be used in the design and assessment of the economic efficiency of high-speed passenger catamarans. The results can be used in Vietnam government program oriented to development of sea transport infrastructure and tourism.

Способы и средства улучшения мореходности, комфортабельности и снижения материалоемкости пассажирского катамарана

Object and purpose of research. This paper discusses passenger catamarans. Its purpose is to find methods and means to improve seakeeping and propulsion performance in waves, reduce external structural loads, improve comfort and reduce material consumption of catamaran by means of optimally shaped bows and passive motion stabilizers. Materials and methods. The study is based on the methods of ship theory and ship motions, as well as on numerical calculation methods. Main results. Based on the calculation data analysis, this paper suggests principal technical solutions offering high comfort and cost-effectiveness of catamaran. Conclusion. These results could be used for design optimization of comfortable and efficient passenger catamarans.

Pengembangan Terpadu City Tour Semarapura Melalui Ship Approach

The development of Semarapura City Tourism through City Tour has not been running as expected, so it has not been able to increase foreign tourist arrivals and has not been able to improve the economy of the community. The research objective was to identify integrated development of City Tour City Semarapura tourism through the SHIP Approach. This study uses a qualitative descriptive approach. Data collection methods used in this study were observation and interviews. The theory used in this study is the Tourism Area Life-Cycle, explaining the position of development of Semarapura tourism. SHIP theory (systemic, holistic, interdiciplinary, and participatory) to describe and explain how the integrated development of City Tour in Semarapura City. The integrated form of City Tour tourism in Semarapura city is carried out by designing tourism models with improvements to the previous City Tour program and designing new tour packages, with additional classes for each package. Puppet painting class, weaving class, metal craft / kepeng money making class and brown sugar making class. The development of City Tour with the addition of tourist classes will provide experience for foreign tourists who visit and have a positive impact on the economy of the community through active participation from all stakeholders.&#x0D; Keywords: Integrated development, Semarapura city tourism, SHIP Approach

The Contribution of Academician Yu. A. Shimansky to the Development of Arctic Shipbuilding

Academician Yulian Alexandrovich Shimansky (1883–1962), an outstanding Russian scientist and shipbuilder, is known for his works in the field of structural mechanics, ship theory and ship design. His monograph “Conventional indicators of a vessel’s ice performance”, published as a separate volume of “Trudy Arkticheskogo nauchno-issledovatelskogo instituta [Proceedings of the Arctic Institute]” (ANII) in 1938, is well known to the specialists in sea ice technology. This work has played an important role in the development of sea ice technology and in designing icebreakers and ice-going vessels both in Russia / USSR and worldwide. The reviews of Shimansky’s contributions to Arctic shipbuilding are usually limited to the analysis of this work. The new materials from the archival documents and two publications that are practically unknown to the researchers allow to considerably broaden the knowledge about his role in the emergence of the studies on the vessels’ ice performance at one of the turning points in the development of sea ice technology: the creation of the first ever ice model basin. Immediately after the end of the Great Patriotic War in 1945, the ANII in Leningrad set out to implement the plans for the creation of the experimental base for studying the processes of icebreakers and ice-going vessels’ motion in ice, i. e. the ice model basin. Shimansky became actively engaged in this work from the very beginning. The archival documents demonstrate his role in the creation of the first ice model basin and the articles rediscovered by us allow to reconstruct the process of creating the theory of a vessel’s motion in ice by Shimansky that is still employed in all ice model basins across the world.

Data-Based Modelling of Ship Propulsion for A 2500 TEU Feeder Container Ship

A sea-going vessel will always face the risk of rough weather along with its voyages. The focus of this paper is on the creation of a data-based model to estimate the power increase or speed loss due to the influence of weather, by using resistance estimation theories and added resistance approximation methods along with additional assisting tools. Furthermore, a theoretical simulation is done in order to benchmark and correct the model setup. The analysis of simulation results shows that at the available data range, the model proves reasonably precise within its capabilities, for academic applications. The general behavior of the model complies with common ship theory, however, does not perfectly resemble the speed-power relation of the ship’s recorded data averages. The analysis suggests that the model is most compatible with the shipload draft of 9,0 to 9,5 meters and within the speed of 19 to 22 knots. The lack of data outside the typical operating range disables the ability to verify the model correspondingly. The theoretical simulation proves valuable in assessing ship data-based models.

Current trends in the development of dry cargo carriers for coastal, mixed and inland navigation

Object and purpose of research. This paper discusses characteristics and technical condition of dry cargo ships of limited sea, mixed and inland navigation in order to describe a methodology that allows predicting the composition of the fleet in the medium term.&#x0D; Materials and methods. This study relied on the database of Marine Engineering Bureau (MEB), register books of classification societies, as well as on initial drawings for baseline designs of ships under consideration. The work followed common methods of ship theory and ship design, as well as of naval structural mechanics, analysis and statistics.&#x0D; Main results. A prediction is given for fleet composition and structure until the year 2030, including the ships built after the year 2000, including the newbuilding orders for years 2020–2022.&#x0D; Conclusion. Today, there are about 1,052 dry cargo vessels in operation, 79 % of which are "old", and 21 % were built after the year 2000. Dry-cargo vessels of Volgodonmax class are still the most popular. Due to shallow water depth, these ships cannot be made bigger, so the only way to increase their cargo capacity is to increase their block coefficient and reduce lightship displacement.&#x0D; The first challenge is fully solved by "super-ample" lines currently adopted by MEB for mixed-navigation vessels like RSD59, RSD62, RSD79. As for the reduction of lightship displacement, i.e. steel weight, all the attempts to improve MEB solutions on ships of other designs have so far led to the opposite result, i.e. greater metal consumption and accordingly lower cargo capacity. Thus, it has been practically established that the only way to reduce lightship weight is to apply lighter materials.

Michell Investigation of the Significant Influence on the Hydrodynamic of a Warp-Chine Pentamaran

This study attempted to investigate the hydrodynamic performance of various pentamaran configurations with a focus on the interference flow around the component hulls. A computer simulation was conducted based on Michell’s thin ship theory alongside a commercial CFD computation as a comparison. Experiments in the towing tank were performed to validate the numerical calculations, resulting in some hydrodynamic characteristics on the far-field wave pattern, wave interference, wave resistance, and total resistance. Analyses on both transversal and divergent waves were performed to assess the magnitude of wave resistance occurring due to the placement of the side hull to the main hull. Analyses on both waves were also conducted to assess the magnitude of wave resistance due to the placement of outriggers. Looking at the results, numerical calculations based on Michell’s theory were in parallel with experimental data, particularly at Fn greater than .4. Michell’s theory was observed as doing a little preferable agreement with the results of experiments than CFD. Besides, flow patterns obtained numerically from Michell’s and CFD analyses appeared as identical to photographs observed in a towing tank. This investigation identified that a configuration with aligning placement of the main to side hull on the formation of arrow tri-hull, near the Kelvin angle, would cancel the wave formed by the leading hull and can be used as a practical setting to reduce the total wave resistance.

Hydrodynamic hull form optimization of fast catamarans using surrogate models

ABSTRACT This paper demonstrates the practical benefit of using efficient computational methods to optimize fast catamarans hydrodynamically. The development of a simplified panel method, which is based on thin ship theory, and the validation of the associated code for the prediction of the calm water resistance of twin-hull vessels is presented. The method was applied in the multi-objective optimization of a fast, zero-emission, battery-driven catamaran by a genetic algorithm, while considering the ensuing design constraints. Results of the study were compared with resistance predictions from a non-linear Rankine panel method and a viscous CFD solver. Moreover, surrogate models were implemented to speed up the optimization process involving several hundred parametrically generated designs. The proposed simplified panel method in connection with a empirical correction for the stern flow proved very valuable in the resistance prediction and hull form optimization of fast catamarans and of slender hulls in general.

The influences of diversity hull shapes and outriggers arrangement in pentamaran systems

The wave flow pattern builds up along the hull and expansion flow behind the hull is absorbing the energy from the ship as a resistance. The ship’s resistance and the behaviour of its components are significant in estimating the propulsion of the ship, which positively influences fuel consumption. The aimed of this work was investigating the influence of two hull forms and its outriggers arrangement in pentamaran systems. The investigating was in wave resistance, interference, and far-field wave spectrum. This study focused on warp-chine and Wigley hull shapes by comparing a computation which was based on Michell’s thin ship theory and various tests in clearance and stagger of side hulls. The results of this study founded the resistance coefficients based on Michell’s approach agreed with towing test results at Fn > 0.5. Besides, wave resistance for warp-chine configurations was established to be much better than Wigley except at Fn < 0.5. High coefficient reduction for warp-chine hulls was generated with a setting where the main hull to side hull on a formation as an arrow trimaran near to Kelvin angle. As for Wigley, the high reduction was produced by a configuration where the front-side hull and the stern-side hull were in line. Then, captured wave patterns of the towing test exhibited a fit visual with the computation, in which Wigley hulls produced a more significant wave than warp-chine hulls.

Hydrodynamic Testing of a High Performance Skiff at Model and Full Scale

Abstract: This study examines the hydrodynamic performance of a high performance skiff hull using three different physical testing techniques which may be used in early stage design for assessment of the upright resistance of sailing vessels. The hull chosen as a benchmark form is a high-speed hard-chine sailing dinghy, typical of modern trends in skiff design, and is broadly similar to some high performance yacht hulls. The 4.55 m hull was tested at full scale in a moderate size towing tank, at 1:2.5 scale in the same tank, and at full-scale by towing on open water. The work presented here builds on the study of Day &amp; Cameron (2017), with the model tests repeated and re-analyzed in the present study and additional results presented. The challenges of full-scale open-water testing are discussed and several potential improvements in practice are identified for future work. Results show that the open water testing broadly matches well with model-scale tank testing, with the mean discrepancy in the measured resistance between the two around 4% over the speed range tested after correction for the presence of the rudder. Agreement is initially less good for the full-scale hull in the tank for higher speeds, both for resistance and trim. ITTC guidelines suggest that blockage may be an issue for the full-scale boat in this size of tank; comparison of the results suggests that blockage, and/or finite depth effects for the full-scale hull in the tank present a substantial problem at the higher speeds. A correction approach for the wave resistance of the full scale results using a calculation based on a linear thin ship theory is effective in this case, and results show that the full scale and model scale tests agree satisfactorily for the majority of the speed range after this correction. In addition to upright resistance in calm water, results are presented for the impact of small waves, the addition of the rudder, and variations in displacement and trim on resistance for a skiff hull. Finally, the results are compared with predictions from the well-known Delft series regression equations, Savitsky's methods, and a thin ship calculation. The thin ship approach gives good agreement for the case in which the hull is trimmed bow-down and the transom is not immersed, while the Savitsky pre-planing approach gives good agreement for the level trim case. The Delft series and Savitsky planing hull approaches do not give good agreement with physical measurements.

Hydrodynamic Testing of a High Performance Skiff at Model and Full Scale

. This study examines the hydrodynamic performance of a high performance skiff hull using three different physical testing techniques which may be used in early stage design for assessment of the upright resistance of sailing vessels. The hull chosen as a benchmark form is a high-speed hard-chine sailing dinghy, typical of modern trends in skiff design, and is broadly similar to some high performance yacht hulls. The 4.55 m hull was tested at full scale in a moderate size towing tank, at 1:2.5 scale in the same tank, and at full-scale by towing on open water. The work presented here builds on the study of Day &amp; Cameron (2017), with the model tests repeated and re-analyzed in the present study and additional results presented.The challenges of full-scale open-water testing are discussed and several potential improvements in practice are identified for future work. Results show that the open water testing broadly matches well with model-scale tank testing, with the mean discrepancy in the measured resistance between the two around 4% over the speed range tested after correction for the presence of the rudder. Agreement is initially less good for the full-scale hull in the tank for higher speeds, both for resistance and trim. ITTC guidelines suggest that blockage may be an issue for the full-scale boat in this size of tank; comparison of the results suggests that blockage, and/or finite depth effects for the full-scale hull in the tank present a substantial problem at the higher speeds. A correction approach for the wave resistance of the full scale results using a calculation based on a linear thin ship theory is effective in this case, and results show that the full scale and model scale tests agree satisfactorily for the majority of the speed range after this correction.In addition to upright resistance in calm water, results are presented for the impact of small waves, the addition of the rudder, and variations in displacement and trim on resistance for a skiff hull. Finally, the results are compared with predictions from the well-known Delft series regression equations, Savitsky's methods, and a thin ship calculation. The thin ship approach gives good agreement for the case in which the hull is trimmed bow-down and the transom is not immersed, while the Savitsky pre-planing approach gives good agreement for the level trim case. The Delft series and Savitsky planing hull approaches do not give good agreement with physical measurements.

Simulation of Kelvin wakes in optical images of rough sea surface

Kelvin wake is one of the common wakes generated by moving ships and contains rich information about ships. In this paper, free wave elevations of Kelvin wake are calculated based on the Michell thin ship theory combined with a point source perturbation model. The probability density function of sea surface slopes is introduced to calculate the specular reflection of sunlight and skylight and the refraction of scattered light underwater. Satellite-detected Kelvin wakes are then simulated by adding surface specular reflectance and water-leaving reflectance. Simulation results agree well with satellite measurements. The specular reflection of sunlight is the decisive factor affecting the features of Kelvin wakes according to the simulation results. The main factors that influence the specular reflection of sunlight, such as the incident direction and observation direction, ship parameters, and background environment, are discussed. This study is helpful for wake detection and provides a preliminary theoretical method for the retrieval of ship information.

Warp-chine on pentamaran hydrodynamics considering to reduction in ship power energy

The proper shape of the ship was resulting lowering shear stress that caused reduction on energy losses in the boundary layer, vortices and flow separation which prevent an increase pressure in the aftbody. Multihull had a much lower resistance components (shear stress and pressure) with the result that requires significantly less horsepower (power energy) than monohull. The total resistance of multihull not only the sum of the individual resistances of each hull. There were interactions between main hull and side hull related to stagger, clearance and speeds. This research was to investigate characteristics of pentamaran based on Michell’s thin ship theory and be adjusted with the experimental on towing test for several configurations on clearance and stagger. The pentamaran with an arrow formation consist of main hull represents a hard chine recommended from Savitsky model and side with V shape, which each of two side hulls located in the same longitudinal. Changing of side hull on clearance strongly affects the resistance characteristics than stagger. The configuration of pentamaran with centerline of the main hull to each of front-side hull approximately 15o-18o could be an effective manner to reduce resistance. In general, thin ship theory from Michell to prediction coefficient component resistance of model with warp-chine yields quite good results with the experiments at Fn > 0.4.