Editorial

5 pages, 196 KiB

Open AccessEditorial

by Serge Sutulo and C. Guedes Soares

J. Mar. Sci. Eng. 2023, 11(5), 911; https://doi.org/10.3390/jmse11050911 - 24 Apr 2023

Viewed by 1865

Ship hydrodynamics and dynamics is a rather old, traditional branch of applied mechanics and also of naval architecture [...] Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

Research

Jump to: Editorial, Review

26 pages, 10165 KiB

Open AccessArticle

Research on the Karhunen–Loève Transform Method and Its Application to Hull Form Optimization

by Haichao Chang, Chengjun Wang, Zuyuan Liu, Baiwei Feng, Chengsheng Zhan and Xide Cheng

J. Mar. Sci. Eng. 2023, 11(1), 230; https://doi.org/10.3390/jmse11010230 - 16 Jan 2023

Cited by 3 | Viewed by 1428

Abstract

Hull form optimization becomes prone to the curse of dimensionality as the number of design variables increases. The traditional sensitivity analysis method requires massive computational fluid dynamics (CFD) computations and analyzing the effects of all variables on the output; thus, it is extremely [...] Read more.

Hull form optimization becomes prone to the curse of dimensionality as the number of design variables increases. The traditional sensitivity analysis method requires massive computational fluid dynamics (CFD) computations and analyzing the effects of all variables on the output; thus, it is extremely time-consuming. Considering this, the development of a rapid and effective dimensionality reduction method is particularly important. The Karhunen–Loève (K–L) transform method projects data from a high-dimensional space onto a low-dimensional space in the direction of the eigenvectors corresponding to large-variance eigenvalues. It extracts the principal components that represent the hull offset information to represent the hull geometric characteristics by analyzing the relationship between the variables in the sample offset matrix. The geometric information matrices of new hull forms can be rapidly reconstructed from the principal components. Compared with direct optimization methods, fewer variables are used to control the deformation of the hull form from the perspective of geometric deformation, avoid a large number of CFD calculations, and improve the efficiency of optimization. This study examined the relevant K–L matrix solution methods and the corresponding hull form reconstruction methods and proposed eigenvalue-based hull form reconstruction equations. The K–L transform method was combined with a previously developed multidisciplinary platform for a comprehensive optimization of ship hydrodynamic performance for hull form optimization, and its effectiveness was verified by using it to optimize DTMB 5415. The results showed that the K–L transform–based dimensionality reduction method significantly reduces the time consumption of optimization while maintaining an acceptable optimization performance. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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20 pages, 7053 KiB

Open AccessArticle

Numerical Evaluation of the Wave-Making Resistance of a Zero-Emission Fast Passenger Ferry Operating in Shallow Water by Using the Double-Body Approach

by Suleyman Duman, Evangelos Boulougouris, Myo Zin Aung, Xue Xu and Amin Nazemian

J. Mar. Sci. Eng. 2023, 11(1), 187; https://doi.org/10.3390/jmse11010187 - 11 Jan 2023

Cited by 2 | Viewed by 1444

Abstract

The consideration of shallow water effects has gained in importance regarding inland operations. The interaction between the keel and the riverbed affects the hydrodynamic characteristics of marine vessels. The highly complex nature of the interference phenomenon in catamarans makes the shallow water problem [...] Read more.

The consideration of shallow water effects has gained in importance regarding inland operations. The interaction between the keel and the riverbed affects the hydrodynamic characteristics of marine vessels. The highly complex nature of the interference phenomenon in catamarans makes the shallow water problem more complicated as compared to monohulls. Hence, catamarans are very sensitive to speed changes, as well as to other parameters, such as the shallow water effects. This makes the design of catamarans more challenging than their monohull equivalents. At lower Froude numbers, the higher importance of the frictional resistance makes the greater wetted surface of the catamaran a disadvantage. However, at higher speeds, there is the potential to turn their twin hulls into an advantage. This study aims to investigate the wave-making resistance of a zero-carbon fast passenger ferry operating in shallow water. The URANS (unsteady Reynolds-averaged Navier–Stokes) method was employed for resistance simulations. Then, the double-body approach was followed to decompose the residual resistance into viscous pressure and wave-making resistance with the help of the form factors of the vessel calculated at each speed. The characteristics of the separated wave-making resistance components were obtained, covering low, medium, and high speeds. Significant findings have been reported that contribute to the field by providing insight into the resistance components of a fast catamaran operating in shallow waters. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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17 pages, 8426 KiB

Open AccessArticle

Research on PID Parameter Tuning and Optimization Based on SAC-Auto for USV Path Following

by Lifei Song, Chuanyi Xu, Le Hao, Jianxi Yao and Rong Guo

J. Mar. Sci. Eng. 2022, 10(12), 1847; https://doi.org/10.3390/jmse10121847 - 01 Dec 2022

Cited by 11 | Viewed by 1786

Abstract

Unmanned surface vessels (USVs) are required to follow a path during a task. This is essential for the USV, especially when following a curvilinear path or considering the interference of waves, and this work has been proven to be complicated. In this paper, [...] Read more.

Unmanned surface vessels (USVs) are required to follow a path during a task. This is essential for the USV, especially when following a curvilinear path or considering the interference of waves, and this work has been proven to be complicated. In this paper, a PID parameter tuning and optimizing method based on deep reinforcement learning were proposed to control the USV heading. Firstly, the Abkowite dynamics model with three degrees of freedom (DOF) is established. Secondly, the guidance law on the line-of-sight (LOS) method and the USV heading control system of the PID controller are designed. To satisfy the time-varying demand of PID parameters for guiding control, especially when the USV moves in waves, the soft actor–critic auto (SAC-auto) method is presented to adjust the PID parameters automatically. Thirdly, the state, action, and reward functions of the agent are designed for training and learning. Finally, numerical simulations are performed, and the results validated the feasibility and validity of the feasibility and effectiveness of the proposed method. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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20 pages, 9892 KiB

Open AccessArticle

Assessment of the Roll Derivatives of Different Surface Ships Based on Numerical Pure Roll Simulation

by Thi Loan Mai, Anh Khoa Vo, Hyeon Kyu Yoon and Dong Kyou Park

J. Mar. Sci. Eng. 2022, 10(11), 1702; https://doi.org/10.3390/jmse10111702 - 09 Nov 2022

Cited by 2 | Viewed by 1326

Abstract

Among the 6 degrees of freedom (6-DoF), excessive roll motion is the most dangerous cause of ships capsizing. However, when analyzing the maneuverability of surface ships, the roll components have usually been ignored. It is widely known that the influence of roll moment [...] Read more.

Among the 6 degrees of freedom (6-DoF), excessive roll motion is the most dangerous cause of ships capsizing. However, when analyzing the maneuverability of surface ships, the roll components have usually been ignored. It is widely known that the influence of roll moment becomes significant for surface ships with low GM (metacentric height) and high speed. This paper examines the pure roll test for several surface ships to assess the roll-related hydrodynamic derivatives of added mass and damping in maneuvering. The objective ships are the KRISO Container Ship (KCS), David Taylor Model Basin (DTMB), Office of Naval Research Tumblehome (ONRT), and Delft 372 catamaran, where the DTMB and ONRT ships are equipped with complementary bilge keels as damping devices and have a small GM, which the Delft 372 catamaran does not have. The flow during pure roll is analyzed by the Computational Fluid Dynamics (CFD) simulation method that allows the complex flow around ships to be captured, especially when the bilge keel and skeg are considered. The results indicate that the roll moment is greatest in the catamaran. Since the roll moments of the DTMB and ONRT are larger than that of the KCS, bilge keels and surface shape also contribute to increasing roll damping moment. In addition, a comparison of the damping derivatives due to roll rate with results obtained from another method indicates that CFD simulation is capable of accurately predicting the roll-related derivatives, which is difficult to perform by the experiment method. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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14 pages, 2056 KiB

Open AccessArticle

Towards Fuel Consumption Reduction Based on the Optimum Contra-Rotating Propeller

by Mina Tadros, Manuel Ventura and C. Guedes Soares

J. Mar. Sci. Eng. 2022, 10(11), 1657; https://doi.org/10.3390/jmse10111657 - 04 Nov 2022

Cited by 7 | Viewed by 2031

Abstract

This paper presents the effect of selecting a contra-rotating propeller (CRP) for a bulk carrier at the engine operating point with minimum fuel consumption, as well as ensuring the safety of the propeller in terms of cavitation and noise. Using a developed optimization [...] Read more.

This paper presents the effect of selecting a contra-rotating propeller (CRP) for a bulk carrier at the engine operating point with minimum fuel consumption, as well as ensuring the safety of the propeller in terms of cavitation and noise. Using a developed optimization model, the geometry of a CRP was selected for different propeller diameters, the same propeller diameter as that of a fixed pitch propeller (FPP) installed on the bulk carrier, and at 90% of the FPP diameter. Additionally, each case was optimized with both no-cup and heavy-cup configurations. In general, the CRP showed better performance than the FPP in terms of efficiency, cavitation, and fuel economy. At the same time, the level of performance was increased when considering the CRP cupping percentage. It was concluded that the CRP can achieve a gain in fuel economy of up to 6.2% in a no-cup configuration when compared to an FPP, and up to 11.7% with a cupped configuration. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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21 pages, 4307 KiB

Open AccessArticle

A New Theoretical Dynamic Analysis of Ship Rolling Motion Considering Navigational Parameters, Loading Conditions and Sea State Conditions

by José M. Pérez-Canosa, José A. Orosa, María Isabel Lamas Galdo and Juan José Cartelle Barros

J. Mar. Sci. Eng. 2022, 10(11), 1646; https://doi.org/10.3390/jmse10111646 - 03 Nov 2022

Cited by 4 | Viewed by 1595

Abstract

Despite the IMO’s efforts and the large quantity of research carried out over the years concerning the sudden loss of stability in fishing vessels, and even the damage done to merchant fleets due to cargo shifting, accidents with very relevant consequences continue to [...] Read more.

Despite the IMO’s efforts and the large quantity of research carried out over the years concerning the sudden loss of stability in fishing vessels, and even the damage done to merchant fleets due to cargo shifting, accidents with very relevant consequences continue to occur. This paper can be considered as a continuation of the recent research of authors which was carried out with ships in static conditions, with pure beam seas and without resistance. The aim of the present research is to provide a reference for ships’ operators to improve the ship’s behavior and seakeeping, to alter the ship’s loading conditions or the navigational parameters (heading and speed), and even be aware of the time available to carry out these modifications before reaching dangerous situations. For this, all sea state conditions were mathematically modelled for, including the ship’s rolling motion both in static and in realistic and dynamic conditions, with the waves influencing the vessel by coming from any direction. Relevant results of easy comprehension for ships’ operators are shown in each of the models, which were validated with a representative real case study. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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22 pages, 5480 KiB

Open AccessArticle

Longitudinal Vibration Transmission Control of Marine Propulsion Shafting with Friction Damper Integrated into the Thrust Bearing

by Ganbo Zhang, Yao Zhao and Wei Chu

J. Mar. Sci. Eng. 2022, 10(10), 1555; https://doi.org/10.3390/jmse10101555 - 20 Oct 2022

Cited by 2 | Viewed by 1470

Abstract

Propeller-induced longitudinal vibration resonance in marine propulsion shafting systems causes great harm to the hull structure and is the primary source of shipboard noise. Integrating a friction damper with designed parameters into thrust bearings can prevent these issues. To investigate the performance of [...] Read more.

Propeller-induced longitudinal vibration resonance in marine propulsion shafting systems causes great harm to the hull structure and is the primary source of shipboard noise. Integrating a friction damper with designed parameters into thrust bearings can prevent these issues. To investigate the performance of the damper-integrated thrust bearing in longitudinal vibration transmission control, an experimental and theoretical study is carried out in a laboratory-assembled test rig, which consists of components similar to the existing marine propulsion system. We developed a prototype of a thrust bearing designed with a friction-damping generation that allows switching from two supporting states, i.e., damper-connected and damper-disconnected states. Furthermore, a nonlinear analysis method for friction dampers is proposed. By this method, the way in which the friction damper changes the dynamic characteristics of the shafting system is analyzed. Based on the test rig, the acceleration frequency response function (AFRF) of the thrust bearing with and without a friction damper is measured. By comparison, the effectiveness of the friction damper is proved. The experimental results show that the friction damper suppresses the shafting longitudinal vibration response in a broadband frequency range and also confirms the stability of the damping effect, which does not change with the shafting rotational speed or static thrust from the propeller. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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29 pages, 8075 KiB

Open AccessArticle

Hydrodynamic Behaviour of a Floating Polygonal Platform Centrally Placed within a Polygonal Ring Structure under Wave Action

by Jeong Cheol Park and Chien Ming Wang

J. Mar. Sci. Eng. 2022, 10(10), 1430; https://doi.org/10.3390/jmse10101430 - 04 Oct 2022

Cited by 1 | Viewed by 1234

Abstract

In this paper, a semi-analytical method has been developed for the hydrodynamic analysis of a floating polygonal platform that is centrally placed within a floating polygonal ring structure under wave action. In view to understand the wave interactions inside the ring structure, the [...] Read more.

In this paper, a semi-analytical method has been developed for the hydrodynamic analysis of a floating polygonal platform that is centrally placed within a floating polygonal ring structure under wave action. In view to understand the wave interactions inside the ring structure, the formulation considers two cases: when the platform and ring structure oscillate individually, and when they oscillate together under wave action. The polygonal shapes of the floating structures can be created from a parametric equation involving the cosine-type radial perturbation. The formulation and computer code are verified by comparing the results with those obtained from the commercial software ANSYS AQWA. When floating ring structures are used, trapped waves are created in the inner water basin resulting in resonance. The interactions among the trapped waves, inner floating platforms and outer ring structures are investigated by performing parametric studies. By changing the dimensions of the platform and ring structure such as the drafts, the radii of platforms and polygonal shapes, their effects on major hydrodynamic quantities may be understood. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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15 pages, 3901 KiB

Open AccessFeature PaperArticle

Mitigation of Hub Vortex Cavitation with Application of Roughness

by Savas Sezen and Mehmet Atlar

J. Mar. Sci. Eng. 2022, 10(10), 1426; https://doi.org/10.3390/jmse10101426 - 04 Oct 2022

Cited by 2 | Viewed by 1658

Abstract

This study investigates the influence of roughness on hydrodynamic performance, especially for the hub vortex—and, hence, hub vortex cavitation—of a benchmark propeller operating under uniform flow conditions using the RANS method. The Schnerr–Sauer cavitation model is also used for modelling the cavitation on [...] Read more.

This study investigates the influence of roughness on hydrodynamic performance, especially for the hub vortex—and, hence, hub vortex cavitation—of a benchmark propeller operating under uniform flow conditions using the RANS method. The Schnerr–Sauer cavitation model is also used for modelling the cavitation on and off the propeller blades. In order to include the effects of roughness in the numerical calculations, the experimentally obtained roughness functions were incorporated with the wall function of the CFD solver. The applicability and effectiveness of the roughness application applied on the propeller hub as a novel concept were explored to mitigate hub vortex cavitation. The results are first validated with experimental data on smooth conditions through the propeller hydrodynamic performance characteristics and cavitation extension. Then, the propeller hub is covered with four different sizes of roughness. The results show that the degradation effects of roughness applied to the hub on propeller performance are negligible, and the maximum efficiency loss is around 0.25% with respect to the smooth condition when the propeller hub was roughened. Favourable impacts of roughness are found for the hub vortex, and hence, hub vortex mitigation. Applying the roughness on the propeller changed the flow properties (e.g., pressure, velocity and turbulent kinetic energy) inside the vortex, enabling the early breakdown of the extension of hub vortices. These flow changes in the presence of roughness result in a mitigation of hub vortex cavitation up to 50% depending on the roughness size with respect to the smooth condition. Thus, this proposed novel concept, application of roughness to the propeller hub, can be used to mitigate hub vortex cavitation, rudder erosion and propeller URN for both newly designed and retrofitted projects by keeping the efficiency loss as minimum as possible. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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23 pages, 14166 KiB

Open AccessArticle

Solitary Wave Interaction with a Floating Pontoon Based on Boussinesq Model and CFD-Based Simulations

by Sarat Chandra Mohapatra, Hafizul Islam, Thiago S. Hallak and C. Guedes Soares

J. Mar. Sci. Eng. 2022, 10(9), 1251; https://doi.org/10.3390/jmse10091251 - 05 Sep 2022

Cited by 9 | Viewed by 1933

Abstract

A mathematical model of solitary wave interaction with a pontoon-type rigid floating structure over a flat bottom is formulated based on Boussinesq-type equations under weakly nonlinear dispersive waves. Based on the higher-order Boussinesq equations, the solitary wave equation is derived, and a semi-analytical [...] Read more.

A mathematical model of solitary wave interaction with a pontoon-type rigid floating structure over a flat bottom is formulated based on Boussinesq-type equations under weakly nonlinear dispersive waves. Based on the higher-order Boussinesq equations, the solitary wave equation is derived, and a semi-analytical solution is obtained using the perturbation technique. On the other hand, brief descriptions of the application of wave2Foam and OceanWave3D on the aforementioned problem are presented. The analytical solitary wave profiles in the outer region are compared with Computational Fluid Dynamics (CFD) and OceanWave 3D model simulations in different cases. The comparison shows a good level of agreement between analytical, wave2Foam, and OceanWave3D. In addition, based on the wave2Foam and coupled OceanWave3D model, the horizontal, vertical wave forces, and the pressure distributions around the pontoon are analysed. Further, the effect of the Ursell number, pontoon length, and water depth on the solitary wave profiles are analysed based on the analytical solution. The paper validates each of the three models and performs intercomparison among them to assess their fidelity and computational burden. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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17 pages, 7248 KiB

Open AccessArticle

Effect of Propeller Cup on the Reduction of Fuel Consumption in Realistic Weather Conditions

by Mina Tadros, Roberto Vettor, Manuel Ventura and C. Guedes Soares

J. Mar. Sci. Eng. 2022, 10(8), 1039; https://doi.org/10.3390/jmse10081039 - 28 Jul 2022

Cited by 12 | Viewed by 2207

Abstract

This paper presents the effect of a propeller cup on the propeller cavitation and the fuel consumption of a bulk carrier in both calm water and different weather conditions towards improving the energy efficiency of the ship and reducing the level of emissions [...] Read more.

This paper presents the effect of a propeller cup on the propeller cavitation and the fuel consumption of a bulk carrier in both calm water and different weather conditions towards improving the energy efficiency of the ship and reducing the level of emissions in terms of design and operation. Based on the propeller optimization model, previously developed that couples NavCad and a Matlab code to select the geometry and the operating point of the propeller at the engine operating point with minimum fuel consumption, the optimized propeller performance is evaluated for different percentages of the cup; light, medium and heavy and compared with the performance of the propeller without a cup in both calm water and several sea states. By evaluating the cavitation criteria, it is concluded that increasing the percentage of cupping reduces the occurrence of cavitation based on the Keller and Burrill methods; moreover, the fuel consumption is reduced by up to 5.4% and 6.6% at the propeller with a higher percentage of cup compared with the uncapped propeller in calm water and among the ship route, respectively. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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23 pages, 8689 KiB

Open AccessArticle

Aerodynamic Load Prediction on a Patrol Vessel Using Computational Fluid Dynamics

by Hafizul Islam, Serge Sutulo and C. Guedes Soares

J. Mar. Sci. Eng. 2022, 10(7), 935; https://doi.org/10.3390/jmse10070935 - 07 Jul 2022

Cited by 4 | Viewed by 2197

Abstract

Aerodynamic loads and moments on a naval patrol vessel are investigated using computational fluid dynamic simulations based on the OpenFOAM solver. After the initial turbulence, time, and grid dependency study, model scale simulations were performed for a wide range of inflow angles to [...] Read more.

Aerodynamic loads and moments on a naval patrol vessel are investigated using computational fluid dynamic simulations based on the OpenFOAM solver. After the initial turbulence, time, and grid dependency study, model scale simulations were performed for a wide range of inflow angles to predict aerodynamic forces and moments acting on the vessel at different heading conditions. For validation, model scale results were compared with wind tunnel data for similar hull forms. Finally, full-scale simulations were performed for a few cases to investigate possible scale effects on simulation results. The revealed scale effect turned out significant only for the yaw moment response. In this study, we aimed to produce reliable aerodynamic load data for the high-speed vessel, which is essential to developing reliable manoeuvring models. We conclude that Computational Fluid Dynamics is capable of providing reliable aerodynamic load predictions for high-speed vessels with sophisticated superstructures, in an economical manner. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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16 pages, 20887 KiB

Open AccessArticle

RANS Prediction of Wave-Induced Ship Motions, and Steady Wave Forces and Moments in Regular Waves

by Qingze Gao, Lifei Song and Jianxi Yao

J. Mar. Sci. Eng. 2021, 9(12), 1459; https://doi.org/10.3390/jmse9121459 - 20 Dec 2021

Cited by 13 | Viewed by 2768

Abstract

The wave-induced motions, and steady wave forces and moments for the oil tanker KVLCC2 in regular head and oblique waves are numerically predicted by using the expanded RANS solver based on OpenFOAM. New modules of wave boundary condition are programed into OpenFOAM for [...] Read more.

The wave-induced motions, and steady wave forces and moments for the oil tanker KVLCC2 in regular head and oblique waves are numerically predicted by using the expanded RANS solver based on OpenFOAM. New modules of wave boundary condition are programed into OpenFOAM for this purpose. In the present consideration, the steady wave forces and moments include not only the contribution of hydrodynamic effects but also the contribution of the inertial effects due to wave-induced ship motions. The computed results show that the contribution of the inertial effects due to heave and pitch in head waves is non-negligible when wave-induced motions are of large amplitude, for example, in long waves. The influence of wave amplitude on added resistance in head waves is also analyzed. The dimensionless added resistance becomes smaller with the increasing wave amplitude, indicating that added resistance is not proportional to the square of wave amplitude. However, wave amplitude seems not to affect the heave and pitch RAOs significantly. The steady wave surge force, sway force and yaw moment for the KVLCC2 with zero speed in oblique waves are computed as well. The present RANS results are compared with available experimental data, and very good agreements are found between them. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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18 pages, 3075 KiB

Open AccessArticle

Effect of Database Generation on Damage Consequences’ Assessment Based on Random Forests

by Luca Braidotti, Jasna Prpić-Oršić and Marko Valčić

J. Mar. Sci. Eng. 2021, 9(11), 1303; https://doi.org/10.3390/jmse9111303 - 21 Nov 2021

Cited by 4 | Viewed by 1392

Abstract

Recently, the application of machine learning has been explored to assess the main damage consequences without employing flooding sensors. This method can be the base of a new generation of onboard decision support systems to help the master during the progressive flooding of [...] Read more.

Recently, the application of machine learning has been explored to assess the main damage consequences without employing flooding sensors. This method can be the base of a new generation of onboard decision support systems to help the master during the progressive flooding of the ship. In particular, the application of random forests has been found suitable to assess the final fate of the ship and the damaged compartments’ set and estimate the time-to-flood. Random forests have to be trained using a database of precalculated progressive flooding simulations. In the present work, multiple options for database generation were tested and compared: three based on Monte Carlo (MC) sampling based on different probability distributions of the damage parameters and a parametric one. The methods were tested on a barge geometry to highlight the main effects on the damage consequences’ assessment in order to ease the further development of flooding-sensor-agnostic decision support systems for flooding emergencies. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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41 pages, 3364 KiB

Open AccessArticle

Mesh Properties for RANS Simulations of Airfoil-Shaped Profiles: A Case Study of Rudder Hydrodynamics

by Suli Lu, Jialun Liu and Robert Hekkenberg

J. Mar. Sci. Eng. 2021, 9(10), 1062; https://doi.org/10.3390/jmse9101062 - 28 Sep 2021

Cited by 8 | Viewed by 6225

Abstract

A good mesh is a prerequisite for achieving reliable results from Computational Fluid Dynamics (CFD) calculations. Mesh properties include mesh types, computational domain sizes, and node distributions. However, in literature, we found no clear consensus about what these properties should be. In this [...] Read more.

A good mesh is a prerequisite for achieving reliable results from Computational Fluid Dynamics (CFD) calculations. Mesh properties include mesh types, computational domain sizes, and node distributions. However, in literature, we found no clear consensus about what these properties should be. In this article, we performed a case study on ship rudders to determine what the suitable mesh properties are for airfoil-shaped profiles. A classic NACA 0012 profile is chosen as an example, and commercial packages ANSYS ICEM are applied for meshing with an ANSYS Fluent solver. With a strategy in consideration of relationships among different mesh properties, a comprehensive parametric investigation is conducted to study the impacts of these properties on the accuracy of rudder hydrodynamic coefficients obtained by CFD methods. The step-by-step study outputs recommended Reynolds numbers, domain sizes, and near- and far-field node distributions for mesh types with distinct topology structures, i.e., C-mesh, O-mesh, H-mesh, and Hybrid-mesh. Specifically, the study shows that a critical Reynolds number is needed for the perspective of efficiency, while a domain extending 60 times of the chord length enables the boundary effects to be negligible. As for node distributions, the near-field nodes should be treated carefully, compared with those in the far-field. After that, corresponding mesh properties for different calculation objectives are illustrated in detail based on the characteristics of mesh types mentioned above. With the proposed strategy for mesh refinements, impacts of different mesh properties on rudder hydrodynamics are clarified and recommended settings are applicable for other airfoil-shaped profiles such as wind turbines and marine propellers. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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19 pages, 4409 KiB

Open AccessArticle

An Approach to Determine Optimal Bow Configuration of Polar Ships under Combined Ice and Calm-Water Conditions

by Hui Li, Yan Feng, Muk Chen Ong, Xin Zhao and Li Zhou

J. Mar. Sci. Eng. 2021, 9(6), 680; https://doi.org/10.3390/jmse9060680 - 21 Jun 2021

Cited by 3 | Viewed by 2389

Abstract

Selecting an optimal bow configuration is critical to the preliminary design of polar ships. This paper proposes an approach to determine the optimal bow of polar ships based on present numerical simulation and available published experimental studies. Unlike conventional methods, the present approach [...] Read more.

Selecting an optimal bow configuration is critical to the preliminary design of polar ships. This paper proposes an approach to determine the optimal bow of polar ships based on present numerical simulation and available published experimental studies. Unlike conventional methods, the present approach integrates both ice resistance and calm-water resistance with the navigating time. A numerical simulation method of an icebreaking vessel going straight ahead in level ice is developed using SPH (smoothed particle hydrodynamics) numerical technique of LS-DYNA. The present numerical results for the ice resistance in level ice are in satisfactory agreement with the available published experimental data. The bow configurations with superior icebreaking capability are obtained by analyzing the sensitivities due to the buttock angle γ, the frame angle β and the waterline angle α. The calm-water resistance is calculated using FVM (finite volume method). Finally, an overall resistance index devised from the ship resistance in ice/water weighted by their corresponding weighted navigation time is proposed. The present approach can be used for evaluating the integrated resistance performance of the polar ships operating in both a water route and ice route. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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Review

Jump to: Editorial, Research

36 pages, 1740 KiB

Open AccessFeature PaperReview

Review on Ship Manoeuvrability Criteria and Standards

by Serge Sutulo and C. Guedes Soares

J. Mar. Sci. Eng. 2021, 9(8), 904; https://doi.org/10.3390/jmse9080904 - 21 Aug 2021

Cited by 11 | Viewed by 3735

Abstract

Possible reduction of the installed power on newly designed merchant ships triggered by requirements of the Energy Efficiency Design Indices (EEDI) raised concern in possible safety degradation and revived interest in manoeuvrability standards to make them capable to compensate for negative effects of [...] Read more.

Possible reduction of the installed power on newly designed merchant ships triggered by requirements of the Energy Efficiency Design Indices (EEDI) raised concern in possible safety degradation and revived interest in manoeuvrability standards to make them capable to compensate for negative effects of underpowering. A substantial part of the present article presents a detailed analytical review of general principles laid in the foundation of consistent safety standards in the naval architecture and analysis of the existing IMO manoeuvrability criteria and standards. Possible ways of extension of the existing standards to embrace situations associated with adverse sea and wind conditions are discussed and modification of the present standards related to the directional stability is considered as one of the possible solutions. At the same time, it was found that introduction of additional standards for the ship controllability in wind is justified, and the second part of the contribution is dedicated to developing a theoretical basis useful for devising such standards. This includes obtaining a set of analytical solutions related to the steady motion in wind and analysis of wind-tunnel data which resulted in simple equations for conservative generalized envelopes for the aerodynamic forces which are especially convenient for standardizing purposes. Possible design decisions aimed at augmentation of the ship’s capacity to resist adverse environmental factors are outlined. Full article

(This article belongs to the Special Issue Ship Dynamics and Hydrodynamics)

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