Journal of Marine Science and Engineering

Research

15 pages, 7301 KiB

Open AccessArticle

Investigating the Effect of Heterogeneous Hull Roughness on Ship Resistance Using CFD

by Soonseok Song, Yigit Kemal Demirel, Claire De Marco Muscat-Fenech, Tonio Sant, Diego Villa, Tahsin Tezdogan and Atilla Incecik

J. Mar. Sci. Eng. 2021, 9(2), 202; https://doi.org/10.3390/jmse9020202 - 16 Feb 2021

Cited by 13 | Viewed by 2784

Abstract

Research into the effects of hull roughness on ship resistance and propulsion is well established, however, the effect of heterogeneous hull roughness is not yet fully understood. In this study, Computational Fluid Dynamics (CFD) simulations were conducted to investigate the effect of heterogeneous [...] Read more.

Research into the effects of hull roughness on ship resistance and propulsion is well established, however, the effect of heterogeneous hull roughness is not yet fully understood. In this study, Computational Fluid Dynamics (CFD) simulations were conducted to investigate the effect of heterogeneous hull roughness on ship resistance. The Wigley hull was modelled with various hull conditions, including homogeneous and heterogeneous hull conditions. The results were compared against existing experimental data and showed a good agreement, suggesting that the CFD approach is valid for predicting the effect of heterogeneous hull roughness on ship resistance. Furthermore, the local distributions of the wall shear stress and roughness Reynolds number on the hull surface were examined to assess the flow characteristics over the heterogeneous hull roughness. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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22 pages, 9552 KiB

Open AccessArticle

A Numerical Swallowing-Capacity Analysis of a Vacant, Cylindrical, Bi-Directional Tidal Turbine Duct in Aligned & Yawed Flow Conditions

by Mitchell G. Borg, Qing Xiao, Steven Allsop, Atilla Incecik and Christophe Peyrard

J. Mar. Sci. Eng. 2021, 9(2), 182; https://doi.org/10.3390/jmse9020182 - 10 Feb 2021

Cited by 3 | Viewed by 1910

Abstract

Introducing a duct along the perimeter of a rotor has been acknowledged to augment turbine performance. The outcome causation due to a bi-directional, cylindrical shroud, however, is uncertain. This study analyses the hydrodynamic swallowing capacity of a true-scale, vacant duct for tidal turbine [...] Read more.

Introducing a duct along the perimeter of a rotor has been acknowledged to augment turbine performance. The outcome causation due to a bi-directional, cylindrical shroud, however, is uncertain. This study analyses the hydrodynamic swallowing capacity of a true-scale, vacant duct for tidal turbine applications in aligned and yawed inlet flow conditions by utilising three-dimensional unsteady computational fluid dynamics. The performance is investigated within free-stream magnitudes of 1 to 7 m.s⁻¹, and a bearing angular range of 0° to 45° with the duct axis. In proportion to the free-stream magnitude, the normalised axial velocity through the duct increases as a result of a diminishment in pressure drag. Within yawed flow, the maximum capacity falls at a bearing of 23.2°, resulting in a performance increase of 4.13% above that at aligned flow conditions. The analysis concludes that the augmentation at yawed flow occurs due to the duct cross-sectional profile lift variation with angle-of-attack. Towards nominal yaw angle, the internal static pressure reduces, permitting a higher mass-flow rate. Beyond the nominal angle-of-attack, flow separation occurs within the duct, increasing pressure drag, thereby reducing the swallowing capacity. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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22 pages, 10515 KiB

Open AccessArticle

Numerical Investigation on Hydrodynamic Characteristics of Immersed Buoyant Platform

by Jinjiang Yao, Xingwei Zhen, Yi Huang and Wenhua Wang

J. Mar. Sci. Eng. 2021, 9(2), 168; https://doi.org/10.3390/jmse9020168 - 06 Feb 2021

Cited by 3 | Viewed by 2052

Abstract

The Next Generation Subsea Production System (NextGen SPS) is considered as a competitive alternative system used for offshore petroleum production in ultra-deep sea based on the artificial seabed technology. The Immersed Buoyant Platform (IBP), which is located at a constant depth below the [...] Read more.

The Next Generation Subsea Production System (NextGen SPS) is considered as a competitive alternative system used for offshore petroleum production in ultra-deep sea based on the artificial seabed technology. The Immersed Buoyant Platform (IBP), which is located at a constant depth below the free surface of the water to minimize wave loading, provides a buoyant stable platform for supporting the well completion equipment. Therefore, the hydrodynamic characteristics of IBP in the currents play an essential role in determining the global responses of NextGen SPS. In this paper, aiming at acquiring an optimum structural form of IBP, the hydrodynamic characteristics of the flow past the cylindrical IBP with different height-to-diameter ratios are systematically investigated by use of the large eddy simulation (LES) approach. The simulations with fifteen different height-to-diameter ratios (

H / D

) are investigated. The Reynolds numbers are ranged from

0.94 \times 10^{6}

to

3.45 \times 10^{6}

. It can be verified that the separated fluid reattaches on the surface of the cylinder when the aspect ratio is between 0.1 and 0.4. Due to the specific shape ratio and obvious 3D effect of the cylindrical IBP, no significant vortex shedding has been clearly observed when the aspect ratio is between 0.1 and 0.4. In the case of

0.4 \leq H / D \leq 5.0

, a series of regular and alternating vortex street shedding appear behind the circular cylinder. The simulation results also show that the recirculation region length behind the cylindrical IBP can be significantly reduced with the decreasing aspect ratio. It can be concluded that the cylindrical IBP performs the best hydrodynamic characteristics when the aspect ratio is between 0.3 and 0.4. The research findings will be of great significance to providing valuable reference and foundation to determine the optimum form of underwater structures, such as the buoyancy cans of the hybrid riser system. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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30 pages, 1810 KiB

Open AccessArticle

Verification and Validation of CFD Based Form Factors as a Combined CFD/EFD Method

by Kadir Burak Korkmaz, Sofia Werner and Rickard Bensow

J. Mar. Sci. Eng. 2021, 9(1), 75; https://doi.org/10.3390/jmse9010075 - 13 Jan 2021

Cited by 13 | Viewed by 3226

Abstract

Predicting the propulsive power of ships with high accuracy still remains a challenge. Well established practices in the 1978 ITTC Power Prediction method have been questioned such as the form factor approach and its determination method. This paper investigates the possibility to improve [...] Read more.

Predicting the propulsive power of ships with high accuracy still remains a challenge. Well established practices in the 1978 ITTC Power Prediction method have been questioned such as the form factor approach and its determination method. This paper investigates the possibility to improve the power predictions by the introduction of a combined CFD/EFD Method where the experimental determination of form factor is replaced by double body RANS computations. Following the Quality Assurance Procedure proposed by ITTC, a best practice guideline has been derived for the CFD based form factor determination method by applying systematic variations to the CFD set-ups. Following the verification and validation of the CFD based form factor method in model scale, the full scale speed-power-rpm relations between large number of speed trials and full scale predictions using the CFD based form factors in combination with ITTC-57 line and numerical friction lines are investigated. It is observed that the usage of CFD based form factors improves the predictions in general and no deterioration is noted within the limits of this study. Therefore, the combination of EFD and CFD is expected to provide immediate improvements to the 1978 ITTC Performance Prediction Method. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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26 pages, 15526 KiB

Open AccessArticle

Inhibition and Hydrodynamic Analysis of Twin Side-Hulls on the Porpoising Instability of Planing Boats

by Jiandong Wang, Jiayuan Zhuang, Yumin Su and Xiaosheng Bi

J. Mar. Sci. Eng. 2021, 9(1), 50; https://doi.org/10.3390/jmse9010050 - 05 Jan 2021

Cited by 11 | Viewed by 2865

Abstract

A comparative analysis of the hydrodynamic performance of a planing craft in the monomer-form state (MFS) and trimaran-form state (TFS) was performed, and the inhibition mechanism of twin side-hulls on porpoising instability was evaluated based on the numerical method. A series of drag [...] Read more.

A comparative analysis of the hydrodynamic performance of a planing craft in the monomer-form state (MFS) and trimaran-form state (TFS) was performed, and the inhibition mechanism of twin side-hulls on porpoising instability was evaluated based on the numerical method. A series of drag tests were conducted on the monomer-form models with different longitudinal locations of the center of gravity (L_cg); the occurrence of porpoising and the influence of L_cg on porpoising by the model was discussed. Then, based on the Reynolds-averaged Navier–Stokes (RANS) solver and overset grid technology, numerical simulations of the model were performed, and using test data, the results were verified by incorporating the whisker spray equation of Savitsky. To determine how the porpoising is inhibited in the TFS, simulations for the craft in the MFS and TFS when porpoising were performed and the influence of side-hulls on sailing attitudes and hydrodynamic performance at different speeds were analyzed. Using the full factor design spatial sampling method, the influence of longitudinal and vertical side-hull placements on porpoising inhibition were deliberated, and the optimal side-hull location range is reported and verified on the scale of a real ship. The results indicate that the longitudinal side-hull location should be set in the ratio (a/L_m) range from 0.1 to 0.3, and vertically, the draft ratio (D_d/T_m) should be less than 0.442. Following these recommendations, porpoising instability can be inhibited, and lesser resistance can be achieved. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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17 pages, 19373 KiB

Open AccessArticle

Numerical Study on Wave-Ice Interaction in the Marginal Ice Zone

by Tiecheng Wu, Wanzhen Luo, Dapeng Jiang, Rui Deng and Shuo Huang

J. Mar. Sci. Eng. 2021, 9(1), 4; https://doi.org/10.3390/jmse9010004 - 22 Dec 2020

Cited by 6 | Viewed by 2063

Abstract

The effect of waves on ice sheet is critical in the marginal ice zone (MIZ). Waves break large sea ice into small pieces and cause them to collide with each other. Simultaneously, the interaction between sea ice and waves attenuates these waves. In [...] Read more.

The effect of waves on ice sheet is critical in the marginal ice zone (MIZ). Waves break large sea ice into small pieces and cause them to collide with each other. Simultaneously, the interaction between sea ice and waves attenuates these waves. In this study, a numerical research is conducted based on a computational fluid dynamics (CFD) method to investigate the response of single ice floe to wave action. The obtained results demonstrate that the sea ice has a violent six degree of freedom (6DoF) motion in waves. Ice floes with different sizes, thicknesses, and shapes exhibit different 6DoF motions under the action of waves. The heave and surge response amplitude operator (RAO) of the sea ice are related to wavelength. Furthermore, the overwash phenomenon can be observed in the simulation. The obtained results are compared with the model test in the towing tank based on artificial ice, and they agree well with test results. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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22 pages, 820 KiB

Open AccessFeature PaperArticle

Numerical Analysis of the Rudder–Propeller Interaction

by Diego Villa, Andrea Franceschi and Michele Viviani

J. Mar. Sci. Eng. 2020, 8(12), 990; https://doi.org/10.3390/jmse8120990 - 04 Dec 2020

Cited by 21 | Viewed by 3880

Abstract

The proper evaluation of the Rudder–Propeller interactions is mandatory to correctly predict the manoeuvring capability of a modern ship, in particular considering the commonly adopted ship layout (rudder often works in the propeller slipstream). Modern Computational Fluid Dynamics (CFD) solvers can provide, not [...] Read more.

The proper evaluation of the Rudder–Propeller interactions is mandatory to correctly predict the manoeuvring capability of a modern ship, in particular considering the commonly adopted ship layout (rudder often works in the propeller slipstream). Modern Computational Fluid Dynamics (CFD) solvers can provide, not only the performance of the whole system but also an insight into the flow problem. In the present paper, an open-source viscous flow solver has been validated against available literature experimental measurements in different conditions. After an extensive analysis of the numerical influence of the mesh arrangement and the turbulent quantities on the rudder provided forces, the study focused its attention on the forces generated by the rudder varying the propeller loading conditions and the mutual position between the two devices. These analyses give a hint to describe and improve a commonly-used semi-empirical method based on the actuator disk theory. These analyses also demonstrate the ability of these numerical approaches to correctly predict the interaction behaviour in pre-stall conditions with quite reasonable computational requests (proper also for a design stage), giving additional information on the sectional forces distribution along the span-wise rudder direction, useful to further develop a new semi-empirical rudder model. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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18 pages, 5156 KiB

Open AccessArticle

Interaction Effect between Hull and Accommodation on Wind Drag Acting on a Container Ship

by Ngo Van He, Ngo Van Hien, Van-Thuan Truong and Ngoc-Tam Bui

J. Mar. Sci. Eng. 2020, 8(11), 930; https://doi.org/10.3390/jmse8110930 - 16 Nov 2020

Cited by 5 | Viewed by 3031

Abstract

In this paper, we present our research on applying the commercial Computational Fluid Dynamics (CFD) code to investigate interaction effect between hull and accommodation on wind drag acting above the water hull surface of a full scale 1200 TEU container ship. With this [...] Read more.

In this paper, we present our research on applying the commercial Computational Fluid Dynamics (CFD) code to investigate interaction effect between hull and accommodation on wind drag acting above the water hull surface of a full scale 1200 TEU container ship. With this purpose, aerodynamic performances and wind drag acting on the ship hull with and without accommodations have been computed. Analyzing the obtained CFD results, the interaction effect between hull and accommodation on aerodynamic performances and wind drag acting on the ship have been found. Various new accommodation shapes have been proposed for the original ship to reduce the interaction effect on wind drag. A drastic reduction in the interaction effect between hull and accommodation on wind drag acting on the ship has been achieved and the obtained results have been shown in this paper. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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Graphical abstract

25 pages, 21123 KiB

Open AccessFeature PaperArticle

A Discrete-Forcing Immersed Boundary Method for Moving Bodies in Air–Water Two-Phase Flows

by Haixuan Ye, Yang Chen and Kevin Maki

J. Mar. Sci. Eng. 2020, 8(10), 809; https://doi.org/10.3390/jmse8100809 - 19 Oct 2020

Cited by 2 | Viewed by 2858

Abstract

For numerical simulations of ship and offshore hydrodynamic problems, it is challenging to model the interaction between the free surface and moving complex geometries. This paper proposes a discrete-forcing immersed boundary method (IBM) to efficiently simulate moving solid boundaries in incompressible air–water two-phase [...] Read more.

For numerical simulations of ship and offshore hydrodynamic problems, it is challenging to model the interaction between the free surface and moving complex geometries. This paper proposes a discrete-forcing immersed boundary method (IBM) to efficiently simulate moving solid boundaries in incompressible air–water two-phase flows. In the present work, the air–water two-phase flows are modeled using the Volume-of-Fluid (VoF) method. The present IBM is suitable for unstructured meshes. It can be used combined with body-fitted wall boundaries to model the relative motions between solid walls, which makes it flexible to use in practical applications. A field extension method is used to model the interaction between the air–water interface and the immersed boundaries. The accuracy of the method is demonstrated through validation cases, including the three-dimensional dam-break problem with an obstacle, the water exit of a circular cylinder, and a ship model advancing with a rotating semi-balanced rudder. The flow field, free-surface profile and force on the immersed boundaries (IBs) are in good agreement with experimental data and other numerical results. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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32 pages, 11088 KiB

Open AccessArticle

Impact of Hard Fouling on the Ship Performance of Different Ship Forms

by Andrea Farkas, Nastia Degiuli, Ivana Martić and Roko Dejhalla

J. Mar. Sci. Eng. 2020, 8(10), 748; https://doi.org/10.3390/jmse8100748 - 26 Sep 2020

Cited by 22 | Viewed by 3556

Abstract

The successful optimization of a maintenance schedule, which represents one of the most important operational measures for the reduction of fuel consumption and greenhouse gas emission, relies on accurate prediction of the impact of cleaning on the ship performance. The impact of cleaning [...] Read more.

The successful optimization of a maintenance schedule, which represents one of the most important operational measures for the reduction of fuel consumption and greenhouse gas emission, relies on accurate prediction of the impact of cleaning on the ship performance. The impact of cleaning can be considered through the impact of biofouling on ship performance, which is defined with delivered power and propeller rotation rate. In this study, the impact of hard fouling on the ship performance is investigated for three ship types, keeping in mind that ship performance can significantly vary amongst different ship types. Computational fluid dynamics (CFD) simulations are carried out for several fouling conditions by employing the roughness function for hard fouling into the wall function of CFD solver. Firstly, the verification study is performed, and the numerical uncertainty is quantified. The validation study is performed for smooth surface condition and, thereafter, the impact of hard fouling on resistance, open water and propulsion characteristics is assessed. The differences in the impact of biofouling on the ship performance are noticed amongst different ship forms. They are mainly influenced by the portion of viscous resistance in the total resistance, relative roughness, roughness Reynolds number and advance coefficient for the self-propulsion point. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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25 pages, 5243 KiB

Open AccessArticle

Numerical Simulation of the Ship Resistance of KCS in Different Water Depths for Model-Scale and Full-Scale

by Dakui Feng, Bin Ye, Zhiguo Zhang and Xianzhou Wang

J. Mar. Sci. Eng. 2020, 8(10), 745; https://doi.org/10.3390/jmse8100745 - 26 Sep 2020

Cited by 16 | Viewed by 6279

Abstract

Estimating ship resistance accurately in different water depths is crucial to design a resistance-optimized hull form and to estimate the minimum required power. This paper presents a validation of a new procedure used for resistance correction of different water depths proposed by Raven, [...] Read more.

Estimating ship resistance accurately in different water depths is crucial to design a resistance-optimized hull form and to estimate the minimum required power. This paper presents a validation of a new procedure used for resistance correction of different water depths proposed by Raven, and it presents the numerical simulations of a Kriso container ship (KCS) for different water depth/draught ratios. Model-scale and full-scale ship resistances were predicted using in-house computational fluid dynamics (CFD) code: HUST-Ship. Firstly, the mathematical model is established and the numerical uncertainties are analyzed to ensure the reliability of the subsequent calculations. Secondly, resistances of different water depth/draught ratios are calculated for a KCS scaled model and a full-scale KCS. The simulation results show a similar trend for the change of model-scale and full-scale resistance in different water depths. Finally, the correction procedure proposed by Raven is briefly introduced, and the CFD resistance simulation results of different water depth/draught ratios are compared with the results estimated using the Raven method. Generally, the reliability of the HUST-Ship solver used for predicting ship resistance is proved, and the practicability of the Raven method is discussed. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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21 pages, 12697 KiB

Open AccessArticle

A New Systematic Series of Foil Sections with Parallel Sides

by Antonio Saporito, Adam Persson, Lars Larsson and Antonio Mancuso

J. Mar. Sci. Eng. 2020, 8(9), 677; https://doi.org/10.3390/jmse8090677 - 03 Sep 2020

Cited by 2 | Viewed by 2292

Abstract

Parallel-sided foil sections are used for centerboards and rudders in sailing dinghy classes and also for struts placed in a fluid flow. The objective of this work is to create a systematic series of parallel-sided sections to be used under different conditions, with [...] Read more.

Parallel-sided foil sections are used for centerboards and rudders in sailing dinghy classes and also for struts placed in a fluid flow. The objective of this work is to create a systematic series of parallel-sided sections to be used under different conditions, with an emphasis on the sailing dinghies 470, 420 and Optimist. The loss, and surprisingly the gain, in performance relative to 4-digit NACA sections are also investigated. A 2D Reynolds-averaged Navier–Stokes solver is used with the k-ω SST turbulence model and the gamma transition criterion. A verification study is carried out based on four grids of systematically varied density, and results compared with experimental data on a NACA 64-006 section. The parallel-sided sections are modeled with rational Bézier curves whose geometrical parameters permit to link the shape of the profile to physical variables, which are systematically varied. Three Reynolds numbers and two angles of attack are investigated. Systematic plots show the influence of the trailing edge angle and nose radius for the different section families, and the optimum combination is presented in a table. Physical explanations of the trends, and of the exceptions, are given in the paper, using flow visualizations as well as pressure and friction plots. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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17 pages, 3782 KiB

Open AccessArticle

Distributed Propulsion Systems for Shallow Draft Vessels

by Ladislav Illes, Tomas Kalina, Martin Jurkovic and Vladimir Luptak

J. Mar. Sci. Eng. 2020, 8(9), 667; https://doi.org/10.3390/jmse8090667 - 29 Aug 2020

Cited by 6 | Viewed by 2639

Abstract

The aim of this study was to investigate the impact of distributed propulsion systems used on inland and coastal navigation in shallow water. Five layouts were assessed by computational fluid dynamics (CFD) simulation. The hull/propulsion layout cases have been analyzed for discrete flow [...] Read more.

The aim of this study was to investigate the impact of distributed propulsion systems used on inland and coastal navigation in shallow water. Five layouts were assessed by computational fluid dynamics (CFD) simulation. The hull/propulsion layout cases have been analyzed for discrete flow speed values in the range 0–6 m/s. All cases have been examined under restricted draft conditions in shallow water with a minimum of 0.3 m under keel clearance (UKC) and under unrestricted draft conditions in deep water. The results show that distributed propulsion consisting of 6 or 8 (in some cases, even more) units produces noticeable higher thrust effects in shallow water than the traditional layout. Under restricted conditions, the thrust increase between two distributed layouts with different numbers of propulsors is higher, in contrast to deep water, where differences in performance are not so significant. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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34 pages, 12927 KiB

Open AccessArticle

Numerical Modelling of the Nearfield Longitudinal Wake Profiles of a High-Speed Prismatic Planing Hull

by Angus Gray-Stephens, Tahsin Tezdogan and Sandy Day

J. Mar. Sci. Eng. 2020, 8(7), 516; https://doi.org/10.3390/jmse8070516 - 14 Jul 2020

Cited by 4 | Viewed by 2412

Abstract

This study investigates the level of accuracy with which Computational Fluid Dynamics (CFD) is capable of modelling the nearfield longitudinal wake profiles of a high-speed planing hull. It also looks to establish how various set-ups influence the accuracy, with a specific emphasis on [...] Read more.

This study investigates the level of accuracy with which Computational Fluid Dynamics (CFD) is capable of modelling the nearfield longitudinal wake profiles of a high-speed planing hull. It also looks to establish how various set-ups influence the accuracy, with a specific emphasis on turbulence modelling. It analyses a hull over a broad range of conditions to provide detailed insight into the strengths and limitations of CFD, comparing the numerical results to the experimental results previously generated by the authors. A quantitative comparison is made for the centreline (CL) and quarterbeam (QB) longitudinal wake profile plots. Following this, a qualitative comparison is made between photos of the flow pattern from the experimental testing and free surface elevation plots from CFD. The study concluded that CFD is an accurate and robust method of modelling the nearfield longitudinal wake profiles of a high-speed planning hull. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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14 pages, 8530 KiB

Open AccessArticle

A Mesh Deformation Method for CFD-Based Hull form Optimization

by Kwang-Leol Jeong and Se-Min Jeong

J. Mar. Sci. Eng. 2020, 8(6), 473; https://doi.org/10.3390/jmse8060473 - 26 Jun 2020

Cited by 9 | Viewed by 3988

Abstract

Computational fluid dynamics (CFD) is an effective tool for ship resistance prediction and hull form optimization. A three-dimensional volume mesh is essential for CFD simulation, and mesh generation requires much time and effort. Mesh deformation can reduce the time for mesh generation and [...] Read more.

Computational fluid dynamics (CFD) is an effective tool for ship resistance prediction and hull form optimization. A three-dimensional volume mesh is essential for CFD simulation, and mesh generation requires much time and effort. Mesh deformation can reduce the time for mesh generation and simulation. The radial basis function (RBF) and inverse distance weighted (IDW) methods are well-known mesh deformation methods. In this study, the two methods are compared and a novel mesh deformation method for hull form optimization is proposed. For the comparison, a circular cylinder polyhedral mesh was deformed to the National Advisory Committee for Aeronautics (NACA) 0012 mesh. The results showed that the RBF method is faster than the IDW method, but the deformed mesh quality using the IDW method is better than that using the RBF method. Thus, the RBF method was modified to improve the deformed mesh quality. The centroids of the boundary layer cells were added to the control points, and the displacements of the centroids were calculated using the IDW method. The cells far from the ship were aligned to the free surface to minimize the numerical diffusion of the volume of fluid function. Therefore, the deformable region was limited by the deformed boundary, which reduced the time required for mesh deformation. To validate its applicability, the proposed method was applied for varying the bow shape of Japan Bulk Carrier (JBC). The resistances were calculated with the deformed meshes. The calculation time was reduced to approximately one-third using the result of the initial hull form as the initial condition. Thus, the proposed mesh deformation method is efficient and effective enough for CFD-based hull form optimization. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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18 pages, 8436 KiB

Open AccessArticle

Numerical Prediction of the Vertical Responses of Planing Hulls in Regular Head Waves

by Emre Kahramanoğlu, Ferdi Çakıcı and Ali Doğrul

J. Mar. Sci. Eng. 2020, 8(6), 455; https://doi.org/10.3390/jmse8060455 - 20 Jun 2020

Cited by 10 | Viewed by 2601

Abstract

The evaluation of the hydrodynamic performance of planing vessels has always been one of the most attractive study fields in the maritime agenda. Resistance and self-propulsion studies have been performed using experimental and numerical methods by researchers for a long time. As opposed [...] Read more.

The evaluation of the hydrodynamic performance of planing vessels has always been one of the most attractive study fields in the maritime agenda. Resistance and self-propulsion studies have been performed using experimental and numerical methods by researchers for a long time. As opposed to this, the seakeeping performance of planing hulls is assessed with 2D approximation methods, but limitedly, while the experimental campaign is not cost-effective for several reasons. With this motivation, pitch and heave transfer functions and accelerations were obtained for a monohedral hull and a warped hull using a state of art commercial Reynolds-averaged Navier–Stokes (RANS) solver, in this study. Moreover, 2-DOF (degree of freedom) dynamic fluid–body interaction (DFBI) equations were solved in a coupled manner with an overset mesh algorithm, to find the instantaneous motion of the body. After verification, obtained numerical results at three different Froude numbers and a sufficiently large wave frequency range were compared with the experiments. The results showed that the employed RANS method offers a very accurate prediction of vertical motions and accelerations for planing hulls. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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22 pages, 5615 KiB

Open AccessArticle

Numerical Simulation of Wave Interaction with Payloads of Different Postures Using OpenFOAM

by Mingwei Yan, Xin Ma, Wei Bai, Zaibin Lin and Yibin Li

J. Mar. Sci. Eng. 2020, 8(6), 433; https://doi.org/10.3390/jmse8060433 - 12 Jun 2020

Cited by 10 | Viewed by 2375

Abstract

A three-dimensional numerical wave tank (NWT) is established with Open Source Field Operation and Manipulation (OpenFOAM) software and waves2foam to investigate wave interaction with payloads with different postures in the process of offshore lifting or lowering. Numerical results of regular wave interaction with [...] Read more.

A three-dimensional numerical wave tank (NWT) is established with Open Source Field Operation and Manipulation (OpenFOAM) software and waves2foam to investigate wave interaction with payloads with different postures in the process of offshore lifting or lowering. Numerical results of regular wave interaction with a vertically suspending cylinder are presented first for validation by comparison with the published data. A series of simulation experiments are carried out, and the forces and the moments exerted by the regular waves on a fixed suspending cylinder payload and a fixed suspending cuboid payload with different postures are presented. It can be concluded from the results that the rotating rectangular payload (cuboid and cylinder) suffers a drastically changed moment when it is initially vertically placed, and the projection area of payload vertical to the force affects the corresponding force. The simulation results also show how the forces and the moments change with different posture angles. With some certain posture, the suspending payload suffers minimum forces and moments. Parametric study for the cuboid payload is done in the case of normal incidence. The influence of the payload’s size and wave parameters on forces and moments are analyzed. All of the numerical simulation results and conclusions provide the fundamentals for further research and safe control of offshore lifting or lowering. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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17 pages, 5942 KiB

Open AccessArticle

Unsteady RANS CFD Simulations of Sailboat’s Hull and Comparison with Full-Scale Test

by Pietro Casalone, Oronzo Dell’Edera, Beatrice Fenu, Giuseppe Giorgi, Sergej Antonello Sirigu and Giuliana Mattiazzo

J. Mar. Sci. Eng. 2020, 8(6), 394; https://doi.org/10.3390/jmse8060394 - 29 May 2020

Cited by 13 | Viewed by 2975

Abstract

The hydrodynamic investigation of a hull’s performance is a key aspect when designing a new prototype, especially when it comes to a competitive/racing environment. This paper purports to perform a fully nonlinear unsteady Reynolds Averaged Navier-Stokes (RANS) simulation to predict the motion and [...] Read more.

The hydrodynamic investigation of a hull’s performance is a key aspect when designing a new prototype, especially when it comes to a competitive/racing environment. This paper purports to perform a fully nonlinear unsteady Reynolds Averaged Navier-Stokes (RANS) simulation to predict the motion and hydrodynamic resistance of a sailboat, thus creating a reliable tool for designing a new hull or refining the design of an existing one. A comprehensive range of speeds is explored, and results are validated with hydrodynamic full-scale tests, conducted in the towing tank facility at University of Naples Federico II, Italy. In particular, this work deals with numerical ventilation, which is a typical issue occurring when modeling a hull; a simple and effective solution is here proposed and investigated, based on the phase-interaction substitution procedure. Results of the computational fluid dynamic (CFD) campaign agree with the experimental fluid dynamic (EFD) within a 2% margin. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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26 pages, 3285 KiB

Open AccessArticle

Viscous Damping Identification for a Wave Energy Converter Using CFD-URANS Simulations

by Marco Fontana, Pietro Casalone, Sergej Antonello Sirigu, Giuseppe Giorgi, Giovanni Bracco and Giuliana Mattiazzo

J. Mar. Sci. Eng. 2020, 8(5), 355; https://doi.org/10.3390/jmse8050355 - 17 May 2020

Cited by 31 | Viewed by 3088

Abstract

During the optimization phase of a wave energy converter (WEC), it is essential to be able to rely on a model that is both fast and accurate. In this regard, Computational Fluid Dynamic (CFD) with Reynolds Averaged Navier–Stokes (RANS) approach is not suitable [...] Read more.

During the optimization phase of a wave energy converter (WEC), it is essential to be able to rely on a model that is both fast and accurate. In this regard, Computational Fluid Dynamic (CFD) with Reynolds Averaged Navier–Stokes (RANS) approach is not suitable for optimization studies, given its computational cost, while methods based on potential theory are fast but not accurate enough. A good compromise can be found in boundary element methods (BEMs), based on potential theory, with the addition of non-linearities. This paper deals with the identification of viscous parameters to account for such non-linearities, based on CFD-Unsteady RANS (URANS) analysis. The work proposes two different methodologies to identify the viscous damping along the rotational degree of freedom (DOF) of pitch and roll: The first solely involves the outcomes of the CFD simulations, computing the viscous damping coefficients through the logarithmic decrement method, the second approach solves the Cummins’ equation of motion, via a Runge-Kutta scheme, selecting the damping coefficients that minimize the difference with CFD time series. The viscous damping is mostly linear for pitch and quadratic for roll, given the shape of the WEC analysed. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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26 pages, 13865 KiB

Open AccessArticle

Numerical Investigation of Unsteady Cavitation Dynamics over a NACA66 Hydrofoil near a Free Surface

by Tiezhi Sun, Qingmo Xie, Li Zou, Hao Wang and Chang Xu

J. Mar. Sci. Eng. 2020, 8(5), 341; https://doi.org/10.3390/jmse8050341 - 11 May 2020

Cited by 7 | Viewed by 2776

Abstract

Cavitation is a typical and unavoidable phenomenon for small waterline ships and high-speed vehicles. It creates a highly complex multiphase flow near the free surface and is primarily represented by the free surface-cavitation interaction. In this paper, the large-eddy method and Schnerr-Sauer cavitation [...] Read more.

Cavitation is a typical and unavoidable phenomenon for small waterline ships and high-speed vehicles. It creates a highly complex multiphase flow near the free surface and is primarily represented by the free surface-cavitation interaction. In this paper, the large-eddy method and Schnerr-Sauer cavitation model are combined to address the effects of a free surface on the cavitation dynamics of a NACA66 hydrofoil. The numerical method is validated by comparing the cavitation morphology and pressure with available experimental data. The results show that the presence of a free surface affects the cavitation evolution and hydrodynamic load characteristics. Compared with the non-free surface case for the same cavitation number, the free surface suppresses the cavitation intensity and increases the frequency of cavitation shedding. Furthermore, an improved dynamic mode decomposition method is applied to investigate the unsteady cavitation flow features. The results show a correlation between the characteristic mode and the flow state. Meanwhile, the presence of a free surface is found to reduce the energy content in each order mode and results in smaller scale of the coherent structure in higher-order modes. Moreover, with increasing distance from the hydrofoil to the free surface, the cavitation intensity increases, as well as the average lift and drag coefficients. In particular, significant free-surface unsteady fluctuations are observed in the wake region. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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24 pages, 18676 KiB

Open AccessArticle

CFD Simulation of Ship Seakeeping Performance and Slamming Loads in Bi-Directional Cross Wave

by Jialong Jiao and Songxing Huang

J. Mar. Sci. Eng. 2020, 8(5), 312; https://doi.org/10.3390/jmse8050312 - 29 Apr 2020

Cited by 22 | Viewed by 4511

Abstract

Accurate prediction of ship seakeeping performance in complex ocean environment is a fundamental requirement for ship design and actual operation in seaways. In this paper, an unsteady Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) solver with overset grid technique was applied to estimate [...] Read more.

Accurate prediction of ship seakeeping performance in complex ocean environment is a fundamental requirement for ship design and actual operation in seaways. In this paper, an unsteady Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) solver with overset grid technique was applied to estimate the seakeeping performance of an S175 containership operating in bi-directional cross waves. The cross wave is reproduced by linear superposition of two orthogonal regular waves in a rectangle numerical wave tank. The ship nonlinear motion responses, bow slamming loads, and green water on deck induced by cross wave with different control parameters such as wave length and wave heading angle are systemically analyzed. The results demonstrate that both vertical and transverse motion responses, as well as slamming pressure of ship induced by cross wave, can be quite large, and they are quite different from those in regular wave. Therefore, ship navigational safety when suffering cross waves should be further concerned. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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17 pages, 3833 KiB

Open AccessArticle

Numerical Simulation and Validation in Scrubber Wash Water Discharge from Ships

by Yong-Seok Choi and Tae-Woo Lim

J. Mar. Sci. Eng. 2020, 8(4), 272; https://doi.org/10.3390/jmse8040272 - 10 Apr 2020

Cited by 8 | Viewed by 2858

Abstract

A regulation on the sulfur emissions of ships sailing in global sea areas has been enforced since 1 January 2020. In this new regulation, ships are required to use low-sulfur fuel oils or to install an after-treatment equipment, such as a scrubber. Open [...] Read more.

A regulation on the sulfur emissions of ships sailing in global sea areas has been enforced since 1 January 2020. In this new regulation, ships are required to use low-sulfur fuel oils or to install an after-treatment equipment, such as a scrubber. Open and hybrid scrubbers wash the exhaust gas using seawater and then discharge the wash water overboard. According to the regulation promulgated by the International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC), the wash water must have a pH of 6.5 or higher at 4 m from the discharge point. Wash water is generally acidic, with a pH of 2.5–3.5, whereas seawater is alkaline, with a pH of approximately 8.2. The wash water is dispersed after being discharged overboard through a nozzle, and its pH is restored through dilution with the surrounding seawater. In this study, the pH was calculated by using a theoretical chemical reaction model, and then the dispersion of wash water was analyzed using CFD simulation. This study describes the process of selecting the appropriate turbulent Schmidt number in a wide range of nozzle diameters. Finally, the appropriate nozzle diameter was determined based on the initial pH of the discharged scrubber wash. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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14 pages, 5511 KiB

Open AccessArticle

Comparative Study of Air Resistance with and without a Superstructure on a Container Ship Using Numerical Simulation

by Jun Seok and Jong-Chun Park

J. Mar. Sci. Eng. 2020, 8(4), 267; https://doi.org/10.3390/jmse8040267 - 09 Apr 2020

Cited by 9 | Viewed by 3378

Abstract

This study investigated the resistance performance of ships, using the air resistance correction method. In general, air resistance is calculated using an empirical formula rather than a direct calculation, as the effect of air resistance on the total resistance of ships is relatively [...] Read more.

This study investigated the resistance performance of ships, using the air resistance correction method. In general, air resistance is calculated using an empirical formula rather than a direct calculation, as the effect of air resistance on the total resistance of ships is relatively smaller than that of water. However, for ships with large superstructures, such as container ships, LNG (liquefied natural gas) carriers, and car-ferries, the wind-induced effects might influence the air resistance acting on the superstructure, as well as cause attitude (trim and sinkage) changes of the ship. Therefore, this study performed numerical simulations to compare the total resistance, trim, and sinkage of an 8000 TEU-class container, ship with and without superstructures. The numerical simulation conditions were verified by comparing them with the study results of the KCS (KRISO Container Ship) hull form. In addition, the differences in the above values between the two cases were compared using the coefficients calculated by the empirical formula to identify the effects on the air resistance coefficient. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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24 pages, 11391 KiB

Open AccessFeature PaperArticle

Virtual Replica of a Towing Tank Experiment to Determine the Kelvin Half-Angle of a Ship in Restricted Water

by Momchil Terziev, Guangwei Zhao, Tahsin Tezdogan, Zhiming Yuan and Atilla Incecik

J. Mar. Sci. Eng. 2020, 8(4), 258; https://doi.org/10.3390/jmse8040258 - 06 Apr 2020

Cited by 5 | Viewed by 3058

Abstract

The numerical simulation of ship flows has evolved into a highly practical approach in naval architecture. In typical virtual towing tanks, the principle of Galilean relativity is invoked to maintain the ship as fixed, while the surrounding water is prescribed to flow past [...] Read more.

The numerical simulation of ship flows has evolved into a highly practical approach in naval architecture. In typical virtual towing tanks, the principle of Galilean relativity is invoked to maintain the ship as fixed, while the surrounding water is prescribed to flow past it. This assumption may be identified, at least partly, as being responsible for the wide-scale adoption of computational solutions within practitioners’ toolkits. However, it carries several assumptions, such as the levels of inlet turbulence and their effect on flow properties. This study presents an alternative virtual towing tank, where the ship is simulated to advance over a stationary fluid. To supplement the present work, the free surface disturbance is processed into Fourier space to determine the Kelvin half-angle for an example case. The results suggest that it is possible to construct a fully unsteady virtual towing tank using the overset method, without relying on Galilean relativity. Differences between theoretical and numerical predictions for the Kelvin half-angle are predominantly attributed to the assumptions used by the theoretical method. The methods presented in this work can potentially be used to validate free-surface flows, even when one does not have access to experimental wave elevation data. Full article

(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)

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