Ship Performance Research Articles

Investigation of Seakeeping Performance of Trawler by the Influence of the Principal Particulars of Ships in the Bering Sea

Investigating ship motion under real conditions is vital for evaluating the seakeeping performance, particularly in the design process stage. This study examined the influence of the principal particulars of a trawler on its seakeeping performance. The wave conditions in the Bering Sea are investigated using available data. The length-to-beam (L/B) and beam-to-draft (B/T) ratios of the ship are changed by 10% for the numerical simulation. The response amplitude operator (RAO) motion, root mean square (RMS) value and sensitivity analysis are calculated to evaluate the influence of the trawler dimensions on ship motions. The peak RAO motion affected the ship motions noticeably because of the resonance at the natural frequency. The L/B and B/T ratios are important geometric parameters of a ship that significantly influence its RMS motion, particularly in the case of roll and pitch. The change in the B/T ratio has a good seakeeping performance based on a comparison of the roll and pitch with the seakeeping criteria. The present results provide insights into the seakeeping performance of ships due to the influence of the principal dimensions in the design stage.

Correction to: Influence of propeller fouling on propulsion performance of an actual ship: a long-term analysis focusing on the power for keeping propeller’s rotation of a controllable pitch propeller

Correction to: Influence of propeller fouling on propulsion performance of an actual ship: a long-term analysis focusing on the power for keeping propeller’s rotation of a controllable pitch propeller

Investigating Fuel Injection Strategies to Enhance Ship Energy Efficiency in Wave Conditions

Abstract The prediction of fuel consumption and resulting transportation costs is a crucial stage in ship design, particularly for conditions involving motion in waves. This study investigates the real-time fuel consumption of a container ship when sailing in waves. The overall ship performance is evaluated using a novel non-linear coupled hull-engine-propeller interaction model. A series of towing tank experiments for hull resistance in waves and propeller performance are conducted. The ship engine is mathematically modelled by a quasi-steady-state model equipped with a linear Proportional-Integrator (PI) governor. Various scenarios of shipping transportation are studied, and the resulting instantaneous fuel consumptions and their correlation to other dynamic particulars are demonstrated. Additionally, daily fuel consumption and fuel cost per voyage distance are presented. It is also shown that the controller can effectively adjust the fuel rate, resulting in minimum fuel consumption. The study concludes that there is no correlation between fuel consumption and the frequency of fuel rates. The present framework and mathematical model can also be employed for ship design and existing ships to predict the total required energy per voyage.

The effect of flow stratification on ship performance: a numerical study

ABSTRACT If a layer of low-density water settles on top of higher density water, such as fresh water melting from a glacier and settling on top of colder seawater, a body of water can stratify into stable, distinct layers. A vessel advancing in such a stratified fluid can generate internal waves between these layers. The generation of internal waves requires energy and thus increases the resistance experienced by the vessel, a phenomenon known as the dead water effect which can result in a severe reduction in speed and loss of steering power. This study uses Computational Fluid Dynamics (CFD) to investigate the increase in ship resistance caused by the dead water effect. The results show that the presence of a stratified flow can increase total resistance approximately sixfold in extreme conditions. At standard operating conditions, total resistance may increase by approximately 6% as a result of flow stratification.

A voyage-level ship performance modelling approach for the simulation of the Finnish-Swedish winter navigation system

The Finnish-Swedish winter navigation system plays an essential role in logistics to the ports surrounded by frozen sea in winter. Coordination of icebreakers is crucial to guarantee sufficient transit speed of merchant ships and minimize the waiting time. Simulation of the winter navigation system provides the opportunity to optimize the system performance and help the planning of future icebreaker fleets. For simulation, estimation of ship performance, such as the actual speed in ice, is essential. Calculation methods to estimate ship performance in such contexts are typically required to be of simple form without the need for heavy computation. Existing ship performance models embedded in route optimization algorithms and winter navigation simulations in the literature are often oversimplified. This paper proposes a systematic ship performance modelling approach which accounts for a wide range of parameters, such as ice condition and parameters, power variation and icebreaker assistance. The approach is validated against real ship voyages. The proposed approach is implemented into a simulation model which simulates the operation of merchant ships and icebreakers on the Baltic Sea. Analyses are conducted on the system level in terms of the waiting time of merchant ships needed for icebreakers as well as the energy consumption.

Ship Performances CFD Analysis of Hydrofoil-Supported High-Speed Catamaran Hull Form

Fast ferries with efficient fuel use are becoming increasingly in demand as fossil fuels become more in short supply and metropolises expand all over the globe in coastal and estuarine environments. These criteria need to be fulfilled by the Hydrofoil Supported Catamaran (HYSUCAT). A catamaran with wings between its demi hulls is known as an HYSUCAT, and it combines the positive traits of both the catamaran (manoeuvrability, big deck area) and the wing in-ground vehicle (excellent lift-to-drag ratio). In this research, a concept design Delft-372 catamaran is refitted with a high Reynolds number foil system to lower its overall resistance. The numerical solution of the Reynolds-averaged Navier–Stokes (RANS) equations employing the k-w SST turbulence model is used to simulate the flow around a high-speed catamaran with a hydrofoil. According to the simulation findings, the hydrofoil-assisted catamaran was determined to be a viable alternative to the current catamaran. This is due to a significant decrease in the overall resistance of the ship, reaching up to 42%, as well as notable improvements in pitch angle, reaching up to 26%.

Effect of lake waves on manoeuvring performance of a model ship

ABSTRACT In this study, we investigate how natural environmental conditions affect a training vessel using a ‘mathematical model of wind and wave’ specific to Lake Silm near Kamionka, Poland. Wind and wave measurements on the lake were conducted. We present the vessel’s trajectory under varying conditions: navigating in restricted waters simulating port conditions with speed readings, and during propeller operation. The control system of the nonlinear autonomous object employed two controllers: a linear matrix inequality controller and an overriding trajectory controller. We assess the impact of nonlinearities in the measured waves. It is shown that the maximum entropy probability distribution conforms more closely to the empirical frequency histogram than the Gaussian distribution. The wave height probability distributions diverge from Rayleigh distributions, indicating slight nonlinear effects. These results enhance the mathematical model of Silm Lake’s wave dynamics.

Numerical simulation of the maneuvering performance of ships in broken ice area

Maneuverability is a critical aspect of ship navigation performance, particularly during polar navigation, where the presence of ice significantly affects maneuverability compared to open water navigation. By coupling the non-smooth discrete element method (NDEM) with the Maneuvering Modeling Group (MMG) model, this paper proposes a numerical model to simulate the maneuvering motion of full-scale ships in broken ice regions. In the proposed model, the ship-ice interaction was solved through NDEM, while the 3-DOF MMG model was utilized to simulate the autonomous navigation movement of ships. Based on the relationship between ship turning radius and ship speed, the critical relationship between ice moment and ice resistance is derived in this paper, which can be used to verify the rationality of simulation results of maneuvering motion. In addition, the effects of ice concentration, size, thickness, and ship speed and rudder angle on the ship's maneuvering trajectory and steering flexibility are analyzed by simulating turning motion and Zig-Zag maneuvers. This provides an effective numerical model to simulate the maneuvering motion of a ship in a broken ice area with low-medium ice concentration.

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.

New approaches to assess and improve ship operating performance

The deterioration in the technical conditions of the main engine, hull, and propeller over time in service is natural and causes adverse effects on ship operating performance, so determining and overcoming this phenomenon is necessary. However, effectively solving this problem is not simple because it is affected by many complex and random factors such as engine deterioration, increased roughness of hull and propeller surfaces, changes in sea state and ship load, etc. In this study, our new approach based on the black-box method and detailed propeller diagrams provides an effective way to assess and improve ship performance both under specific operating conditions and after a period of service. This method was verified and validated with the test data of the Glory Star oil tanker and applied to the Duong River dry cargo ship in Vietnam to determine its performance degradation and provide solutions to overcome this problem. The results showed that after 5 years out of dry dock, the study ship's performance or propulsion efficiency was reduced by about 8.6%, resulting in an increase in fuel consumption of about 6.5% and a decrease in ship speed of about 14.7%. By applying technical solutions such as tuning the engine operating mode and choosing a practical propeller design point, the performance of this ship was greatly improved and brought about high economic and technical efficiency. Especially, the cutting of the propeller edges not only solved the torque-rich phenomena occurring on the study ship's main engine after 5 service years, but also saved 5.1% and 4.9% in hourly fuel consumption, and increased 3.9% and 4.9% in ship speed, calculated for ballast and full load sea trials, respectively.

Analysis of perforated fixed baffle at low filling ratio to reduce sloshing using SPH

Prismatic tanks are used widely in various industrial applications, including marine and petroleum, due to their ease in design and storage capacity. However, these tanks often experience sloshing issues that can affect vessel stability. Sloshing effects can cause undesirable motions and impact the system's overall performance. This study focuses on analyzing the effect of perforated shapes on fixed baffles as a solution to reduce the sloshing effect in prismatic tanks. Baffle or anti-sloshing is an internal partition used to minimize the movement of liquid in the tank. The analysis method uses Smoothed particle hydrodynamics (SPH), which is a particle method or can be referred to as mesh-free computational fluid dynamics. The parameters tested include the perforated shape and the filling ratio of the water filling in the tank. The analysis found that the perforated form of the baffles has a significant effect on reducing the sloshing effect. The perforated shape of the fixed baffles has the same impact on reducing the sloshing effect of the prismatic tank. There is no significant difference in the ability of each baffle shape to overcome the sloshing problem. The findings from this study can guide designers or engineers in designing prismatic tanks that are more stable and reduce the effects of sloshing. Using baffles with the right perforated shape can optimize tank performance in maritime and shipping.

A digital twin for ship structures—R&D project in Japan

Abstract In order to clarify and visualize the real state of the structural performances of ships in operation and establish a more optimal, data-driven framework for ship design, construction and operation, an industry-academia joint R&D project on the digital twin for ship structures (DTSS) was conducted in Japan. This paper presents the major achievements of the project. The DTSS aims to grasp the stress responses over the whole ship structure in waves by data assimilation that merges hull monitoring and numerical simulation. Three data assimilation methods, namely, the wave spectrum method, Kalman filter method, and inverse finite element method were used, and their effectiveness was examined through model and full-scale ship measurements. Methods for predicting short-term extreme responses and long-term cumulative fatigue damage were developed for navigation and maintenance support using statistical approaches. In comparison with conventional approaches, response predictions were significantly improved by DTSS using real response data in encountered waves. Utilization scenarios for DTSS in the maritime industry were presented from the viewpoints of navigation support, maintenance support, rule improvement, and product value improvement, together with future research needs for implementation in the maritime industry.

Power Increase due to Marine Biofouling: a Grey-box Model Approach

This paper proposes a grey-box modelling approach to predict marine biofouling growth and its effects on ship performance. The approach combines empirical or experimental-based white-box models with data-driven black-box models. First, a white-box model is built to predict ship resistance considering a bare hull. This prediction is based on calm water resistance, wind, waves, and temperature differences. Subsequently, marine biofouling growth is predicted using an experimental model that estimates the level of roughness on the ship hull. Finally, a deep extreme learning machine is used as a black-box model, employing a feedforward neural network technique. To test the approach, a superyacht case study was selected as a category of vessel heavily exposed to fouling. The study used a 2-year dataset obtained through a collaboration with Feadship. Results showed that the black-box approach outperforms the white-box approach in predictive capabilities. However, when the knowledge encapsulated in the white-box model is included in the grey-box approach, the model shows the highest prediction accuracy achieved by leveraging less historical data. This study demonstrates the potential of the proposed grey-box approach to accurately predict marine biofouling growth and its effects on ship performance, which can benefit ship operators and designers in improving operational efficiency and reducing maintenance costs.

Experimental and numerical study on the high-speed ship hydrodynamics influenced by an interceptor with varied angle of attack

Efforts to improve the hydrodynamic performance of high-speed ships have been underway for a long time. There are different approaches, one of which is to take advantage of an interceptor. Conventionally, the interceptor blades are mounted vertically on the ship's bottom transom, oriented at a zero-degree angle of attack (AoA). This study comprehensively explores high-speed ships' hulls with and without interceptor configurations, encompassing both negative and positive AoA of the interceptor, conducted through experimental and numerical methods using a fully captive model. The interceptors are strategically positioned and configured. Each configuration was examined under varying AoA settings, with uniform interceptor depths and systematic trim angle adjustments. The Computational Fluid Dynamics (CFD) approach simulates the local flow dynamics around the hull, thoroughly analyzing resistance, pressure distribution, lift force, wave profile, and trim moment. The results indicate that interceptor placement near the keel with AoA adjustments significantly reduces hydrodynamic resistance, while AoA changes have limited impact in other positions. Lift force analysis shows interceptors improve lift compared to the bare hull, but this improvement is not linear across positions. Furthermore, it is observed that adjustments in AoA influence lift, with a negative AoA generally being considered favorable. In summary, carefully considering placement, AoA, and height-to-length ratio is necessary to maximize interceptor advantages.

A comparative analysis of course keeping and turning circle for a 37000 tdw chemical tanker

The maneuvering characteristics of ships represent complex phenomena, which includes their capacity for both maintaining a steady course and turning ability. There are no simple methods for evaluating a ship's performance in these aspects. Furthermore, the flow patterns connected to these phenomena are complex and frequently coupled with other factors. The purpose of this study is to evaluate the course keeping and turning performance for a 37000 tdw chemical tanker. Course-keeping is evaluated based on stability criteria, while empirical relations and numerical simulations using hydrodynamic derivatives from both empirical and computational fluid dynamics (CFD) methods are employed to analyse the turning circle and then compared with data from actual sea trials.

Comparative analysis of the maneuverability performance of a chemical tanker with the power of the propulsion installation PB=6480kw

This article investigates ship maneuverability by conducting and comparing calculations using two distinct computational platforms. The results obtained from these calculations are subsequently compared with real data from the sea trials. A detailed analysis of the discrepancies between theoretical and empirical results provides insights regarding the reliability and precision of each computational platform in assessing ship maneuverability in the naval domain. This research contributes to improving methods for evaluating ship performance and validating computational platforms used in the industry.

Boundary Element Method Analysis of 3D Effects and Free-Surface Proximity on Hydrofoil Lift and Drag Coefficients in Varied Operating Conditions

_ The use of hydrofoils to enhance ship performance raises the scientific issue of free-surface proximity, which is important to consider during the design stage, to feed velocity prediction programs, for instance. Typically, the flow over a shallowly submerged hydrofoil is characterized by the Froude number, the submergence depth-to-chord ratio, the angle of attack, and geometric parameters of the lifting surface. Among these parameters, the present paper investigates the influence of the wing aspect ratio on the lift and drag coefficients of hydrofoils operating near a free surface. For this purpose, rectangular wings with an H105 profile at 2° angle of attack and aspect ratios ranging from 4 to 20 are systematically analyzed using a 3D boundary element method. The free surface is modeled using a linearized Neumann-Kelvin boundary condition. Chord-based Froude numbers of 0.5, 1.1, and 6.3 are studied. The submersion depth is swept between 0.1 and 30 times the foil chord length. The evolution of the normalized lift and drag coefficients with respect to the foil submersion and the aspect ratio is discussed in detail. Flow velocity is shown to play a significant role in the evolution of the lift and drag coefficients with submersion depth, close to the free surface, for all the aspect ratios. Its influence gets reduced by moving away from the free surface. The critical submersion depth, where the free-surface effects cease, is found to increase with higher flow velocity and aspect ratio. Furthermore, both positive and negative correlations between the force coefficients and the aspect ratio are identified, depending on the operating conditions. It is found that when the proximity to the free surface either enhances or impairs a force coefficient relative to its value in unbounded flow, increasing the aspect ratio amplifies this effect. Overall, this study confirms the effectiveness of steady boundary element methods for simulating the flow around hydrofoil wings in the vicinity of a free surface and contributes to further understanding the influence of geometric parameters on hydrofoil performance. Keywords hydrofoil; free surface; aspect ratio; potential flow; boundary element method (BEM)

Air quality forecasting of along-route ship emissions in realistic meteo-marine scenarios

This study introduces a novel framework of metocean prediction and ship performance models that integrate multiple layers of modeling to evaluate the environmental impact of ship emissions. It enables scenario simulations that assess a ship’s performance, estimates pollutant emissions, and simulate the fate of these pollutants in the atmosphere. The study analyzes the fate of NOx, SO2, and PM10 pollutants in the atmosphere using spatially distributed concentration maps. It provides a comprehensive approach to assessing the environmental effects of ships and their emissions and contributes to the field of environmental impact assessment. Case studies are presented to demonstrate the framework’s functionalities, evaluating the interrelationships between adverse meteo-marine conditions, pollutant emissions, and resulting atmospheric diffusion characteristics.

Studi Eksperimen Pengaruh Ekstrak Kulit Nanas terhadap Laju Pertumbuhan Mikrofouling

Biofouling often sticks to the ship's hull, even to the propeller parts and pipes that are submerged in water. The existence of this biofouling has an impact on the ship's performance, reducing it and requiring more fuel, which ultimately contributes significantly to increased costs. Microfouling is one of the stages of biofouling growth that appears in a matter of days to weeks with a size of up to 1 mm which can be characterized by the appearance of a slippery layer on the surface of the specimen. Until now, many antifouling paints, as a means of preventing the occurrence of biofouling, still contain TBT, which has serious side effects as a chemical pollutant. Pineapple peel is a waste that is often found in Indonesia and contains bromelain and tannin which are anti-bacterial. The appearance of bacteria is the first phase in the growth of biofouling which is usually called biofilm, so it is hoped that pineapple peel extract will be able to prevent the emergence of biofilm. To determine the effectiveness of pineapple peel extract, this experimental study was carried out. The method used was a Randomized Block Design on ASTM 36 steel plate which is a certified ship material with 3 variations and 1 control of specimen as follows, 3 specimens as controls, 3 specimens with a ratio of 30% pineapple peel extract, 3 specimens with a ratio of pineapple peel extract. 50%, and 3 specimens with a pineapple peel extract ratio of 70%. Immersion for 7 weeks was carried out at Boom Beach, Banyuwangi by calculating the DGR (Daily Growth Rate) once a week. The DGR results obtained were respectively 0.095 g/day at an extract ratio of 30%, 0.0727 g/day at an extract ratio of 50%, and 0.0730 g/day at an extract ratio of 70%.

Verification of simplified underwater radiated noise estimation tool using Brown's formula

In recent years, the impact of underwater radiated noise from ships on marine life has attracted considerable global attention. Therefore, various research institutions are investigating this phenomenon through research and development efforts. In this study, authors have developed an underwater radiated noise estimation tool that can be used in the early stages of ship design. This tool calculates the underwater radiated noise level by applying Brown's formula, a simple estimation formula for predicting the noise generated by ships. The parameters required for Brown's formula are estimated using HOPE Light, a ship performance estimation software developed by the National Maritime Research Institute. The extent of cavitation is estimated using Burrill's diagram, a tool for assessing the occurrence of cavitation. The accuracy of the developed tool has been verified by comparing its results with full scale measurements of underwater radiated noise levels obtained off-board hydrophone array system.