Journal of Marine Science and Engineering

Research

21 pages, 14688 KiB

Open AccessArticle

Computational Study on Influence Factors and Vortical Structures in Static Drift Tests

by Chen Yang, Ke Zeng, Jilong Chu, Shuxia Bu and Zhang Zhu

J. Mar. Sci. Eng. 2024, 12(5), 789; https://doi.org/10.3390/jmse12050789 - 8 May 2024

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This paper conducted a computational study on the KCS benchmark model at static drift conditions. At the first instance, the roles played by the grid size, turbulence model, and time step are qualitatively and quantitatively analyzed with the orthogonal experimental method (OEM). After [...] Read more.

This paper conducted a computational study on the KCS benchmark model at static drift conditions. At the first instance, the roles played by the grid size, turbulence model, and time step are qualitatively and quantitatively analyzed with the orthogonal experimental method (OEM). After the verification of simulated results compared with experimental data in a Static Oblique Towing Test (OTT), hydrodynamic performance is obtained with the employment of the SST κ-ω turbulence model. The grid size is set as 0.07 m while the time step as 0.01 s. The characteristics of the wake field are illustrated in different forms, such as contours of the free surface, distribution of pressure and hydrodynamic forces, variation of turbulent kinetic energy (TKE), and so on. For a deep insight into the physical mechanisms of the asymmetrical flow field, the Detached Eddy Simulation (DES) method is also utilized to capture vortical structures occurring around the hull, in comparison with results obtained through the Reynolds Averaged Navier Stokes (RANS) model. With the aim of a hydrodynamic derivative estimation or detailed flow characteristics analysis, corresponding selections of the computational method are disparate. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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21 pages, 19037 KiB

Open AccessArticle

Numerical Simulation and Analysis of Added Mass for the Underwater Variable Speed Motion of Small Objects

by Xuanquan Wang, Suwei Xiao, Xinchun Wang and Debo Qi

J. Mar. Sci. Eng. 2024, 12(4), 686; https://doi.org/10.3390/jmse12040686 - 22 Apr 2024

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Abstract

Unlike uniform motion, when an object moves underwater with variable speed, it experiences additional resistance from the water, commonly referred to as added mass force. At present, several methods exist to solve this force, including theoretical, experimental, and simulation approaches. This paper addresses [...] Read more.

Unlike uniform motion, when an object moves underwater with variable speed, it experiences additional resistance from the water, commonly referred to as added mass force. At present, several methods exist to solve this force, including theoretical, experimental, and simulation approaches. This paper addresses the challenge of determining the added mass force for irregularly shaped small objects undergoing variable speed motion underwater, proposing a method to obtain the added mass force through numerical simulation. It employs regression analysis and parameter separation analysis to solve the added mass force, added mass, viscous drag coefficient, and pressure drag coefficient. The results indicate that an added mass force exists during both the acceleration and deceleration of the object, with little difference between them. Under the same velocity conditions, significant differences exist in pressure drag forces, while differences in viscous drag forces are not significant. This suggests that the primary source of added mass force is pressure drag, with viscous drag having little effect on it. During acceleration, the surrounding fluid accelerates with the object, increasing the pressure drag with a high-pressure area concentrating at the object’s front, forming an added mass force that is directed backward. By contrast, during deceleration, the fluid at the object’s front tends to detach, and the fluid at the rear rushes forward, leading to a smaller high-pressure area at the front and a larger one at the rear, reducing the pressure drag and forming an added mass force that is directed forward. By comparing the added mass of a standard ellipsoid obtained from numerical simulation with theoretical values, the regression analysis method is proven to be highly accurate and entirely applicable for solving the added mass of underwater vehicles. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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19 pages, 4528 KiB

Open AccessArticle

Fishing Vessel Bulbous Bow Hydrodynamics—A Numerical Reverse Design Approach

by Héctor Rubén Díaz Ojeda, Sebastian Oyuela, Roberto Sosa, Alejandro Daniel Otero and Francisco Pérez Arribas

J. Mar. Sci. Eng. 2024, 12(3), 436; https://doi.org/10.3390/jmse12030436 - 29 Feb 2024

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Abstract

Naval hydrodynamics typically focus on reducing ship resistance, which can be achieved by incorporating a bulbous bow. This feature is commonly used in the merchant fleet and smaller vessels, such as fishing boats, to minimize wave-making resistance. However, it is important to note [...] Read more.

Naval hydrodynamics typically focus on reducing ship resistance, which can be achieved by incorporating a bulbous bow. This feature is commonly used in the merchant fleet and smaller vessels, such as fishing boats, to minimize wave-making resistance. However, it is important to note that the use of a bulbous bow may not always be necessary or effective in all ship designs. In some cases, fishing ship designs may include a bulbous bow that is not optimized due to the use of procedures and methods intended for larger merchant ships or based on past experience. This study examines the effect of different bow designs, including the bulbous bow, on ship resistance in calm water, with a focus on a typical Argentinian trawler fishing vessel. The objective of this research is to assess the hydrodynamics of various designs for a particular ship by modifying its vessel lines. Firstly, the bulbous bow is removed, and then the reduction in ship resistance achieved by the bulbous bow under different load conditions and speeds is evaluated by comparing the vessel with and without the bulbous bow. The numerical analysis is performed using OpenFOAM, and the results are validated through towing tank experiments. This research indicates that the performance of the bulbous bow varies under different conditions. Therefore, it is recommended to conduct an initial study and a full evaluation of the design and operation alternatives. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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25 pages, 7543 KiB

Open AccessArticle

High-Order Spectral Irregular Wave Generation Procedure in Experimental and Computational Fluid Dynamics Numerical Wave Tanks, with Application in a Physical Wave Tank and in Open-Source Field Operation and Manipulation

by Young Jun Kim, Maxime Canard, Benjamin Bouscasse, Guillaume Ducrozet, David Le Touzé and Young-Myung Choi

J. Mar. Sci. Eng. 2024, 12(2), 227; https://doi.org/10.3390/jmse12020227 - 26 Jan 2024

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Abstract

The accurate generation of a target sea state in numerical or experimental wave tanks is a fundamental line of research for the ocean engineering community. It guarantees the quality and relevance of wave–structure interaction tests. This study presents a reproducible irregular wave generation [...] Read more.

The accurate generation of a target sea state in numerical or experimental wave tanks is a fundamental line of research for the ocean engineering community. It guarantees the quality and relevance of wave–structure interaction tests. This study presents a reproducible irregular wave generation and qualification procedure, accounting for the nonlinear aspects of wave propagation. It can be used for both numerical simulation and experiments. The presented numerical and experimental results are obtained from the OpenFOAM solver and the Ecole Centrale Nantes wave tank facilities, respectively. The procedure comprises two steps: First, the wavemaker motion is calibrated numerically to generate the target wave spectrum at the position of interest. This is achieved with a wavemaker-equipped nonlinear potential flow solver. The open-source HOS-NWT solver, based on the high-order spectral method, was employed in this study. Then, the corrected wavemaker motion is used directly in the experimental wave tank. OpenFOAM simulations were performed to generate waves with the relaxation method, using wave elevation and velocity field data from HOS-NWT. The procedure was finally tested for mild and extreme breaking sea states. The waves generated by the HOS-NWT solver, the experiment, and the OpenFOAM simulation were compared from both stochastic and deterministic perspectives. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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15 pages, 3972 KiB

Open AccessArticle

A Numerical Simulation Study and Effectiveness Evaluation on the Flow Field Effect of Trapezoidal Artificial Reefs in Different Layouts

by Xiaolong Chen, Xuan Che, Yin Zhou, Changfeng Tian and Xinfeng Li

J. Mar. Sci. Eng. 2024, 12(1), 3; https://doi.org/10.3390/jmse12010003 - 19 Dec 2023

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Abstract

The combined release of artificial reefs in different quantities and arrangements leads to different flow field effects. This study designs a small trapezoidal artificial reef. To optimize the quantity and layout of these reefs, trapezoidal reefs in three different layouts were selected for [...] Read more.

The combined release of artificial reefs in different quantities and arrangements leads to different flow field effects. This study designs a small trapezoidal artificial reef. To optimize the quantity and layout of these reefs, trapezoidal reefs in three different layouts were selected for analysis at five different velocity gradients (0.1, 0.5, 1.0, 1.5, and 2.0 m/s). The effects of disposal spacing and layout on the flow field effect of trapezoidal artificial reefs at different flow velocities were simulated using Ansys Fluent. According to the findings: after simulation, flow velocity could indirectly reflect the distribution of upwelling and back eddy, the scale and strength of upwelling increased as flow velocity increased, and the back eddy showed no obvious variation with flow velocity. In transverse combination mode, both the scale and strength of the upwelling and back eddy were maximized when the reef spacing was 1.0 L; in longitudinal combination mode, upwelling and back eddy reached maximum scale and strength when the disposal spacing of the reefs was 1.5 L of a single reef. In 2020, flow mapping and fishery surveys were carried out in the engineering pilot area. The results showed that the number and species of fish populations with 1.5 L spacing in the vertical combination method were significantly higher than those in other forms, and the structure of the fish reef was stable without any flipping or sliding phenomenon. This study can provide a theoretical reference for the design and the actual deployment of artificial reefs to improve the ecological restoration of the water. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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22 pages, 10796 KiB

Open AccessArticle

Large Eddy Simulation of the Flow around a Generic Submarine under Straight-Ahead and 10° Yaw Conditions

by Mo Chen, Nan Zhang, Hailang Sun and Xuan Zhang

J. Mar. Sci. Eng. 2023, 11(12), 2286; https://doi.org/10.3390/jmse11122286 - 1 Dec 2023

Cited by 1 | Viewed by 857

Abstract

Aiming towards a better understanding of the flow field around a fully appended Joubert BB2 submarine model, and in order to complement the experimental investigations of the wake of the hydroplanes and sail, large eddy simulation (LES) with the dynamic Smagorinsky model was [...] Read more.

Aiming towards a better understanding of the flow field around a fully appended Joubert BB2 submarine model, and in order to complement the experimental investigations of the wake of the hydroplanes and sail, large eddy simulation (LES) with the dynamic Smagorinsky model was conducted. Three sets of grids with a maximum grid number of up to 228 million were designed to perform the LES simulation for the Joubert BB2 under 10° yaw conditions, with a freestream Reynolds number based on the local freestream velocity and a hull length of Re_L = 2.2 × 10⁷. Comparisons of the wake of the cruciform appendage were made with experiments to verify the computational accuracy and to examine the influence of the spatial resolution. A satisfactory result was more representative of the experiments with the improvement in grid spatial resolution. The evolution characteristics of three co-rotating vortices originating from the cruciform appendage under the most refined grid arrangement are further described in detail under straight-ahead and 10° yaw conditions. The comparison results show that, in the core-flow region, the resultant velocity, vorticity magnitude, and TKE were stronger and the wake was more complicated under 10° yaw conditions. Tip vortex tracking under 10° yaw conditions exhibited significant three-dimensional characteristics as the wake developed downstream. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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25 pages, 15078 KiB

Open AccessArticle

Parametric Design of a New Float-Type Wave Energy Generator and Numerical Simulation of Its Hydrodynamic Performance

by Yu Zhang and Dongqin Li

J. Mar. Sci. Eng. 2023, 11(11), 2192; https://doi.org/10.3390/jmse11112192 - 17 Nov 2023

Viewed by 1214

Abstract

A novel float-type device for wave energy power generation, designed specifically for offshore wave environments, is introduced as an innovative technology in wave energy utilization. Herein, we present the design concept, structural composition, and energy conversion process of the device, and conduct mathematical [...] Read more.

A novel float-type device for wave energy power generation, designed specifically for offshore wave environments, is introduced as an innovative technology in wave energy utilization. Herein, we present the design concept, structural composition, and energy conversion process of the device, and conduct mathematical modeling and theoretical research on its kinematic and dynamic characteristics. At the same time, we use a numerical wave pool based on the STAR-CCM+ boundary wave making method and damping dissipation method to analyze the motion response and output power of the wave energy generator in a five-order Stokes wave environment within one wave cycle and the entire operating cycle. Finally, in order to develop the best design strategy, we study the effect of changing the structural parameters of the power generation device on the hydrodynamic performance of the device. Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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17 pages, 2077 KiB

Open AccessArticle

Role of Shape and Kinematics in the Hydrodynamics of a Fish-like Oscillating Hydrofoil

by Siddharth Gupta, Atul Sharma, Amit Agrawal, Mark C. Thompson and Kerry Hourigan

J. Mar. Sci. Eng. 2023, 11(10), 1923; https://doi.org/10.3390/jmse11101923 - 5 Oct 2023

Viewed by 950

Abstract

In the present two-dimensional numerical study, we investigate the roles of geometrical parameters of a hydrofoil (shape/curvature of the leading and trailing edges and thickness) and kinematic parameters (phase difference between heave and pitch (

ϕ

)) on the propulsive performance of different-shaped [...] Read more.

In the present two-dimensional numerical study, we investigate the roles of geometrical parameters of a hydrofoil (shape/curvature of the leading and trailing edges and thickness) and kinematic parameters (phase difference between heave and pitch (

ϕ

)) on the propulsive performance of different-shaped hydrofoils oscillating at maximum angles of attack up to

α_{max} = 30^{\circ}

. The study was carried out at a fixed non-dimensional maximum heave to chord ratio

h_{\circ} / C = 0.75

, Strouhal number

S t = 0.25

, and Reynolds number

R e = 5000

. Our findings reveal that hydrofoil performance and stability improve with leading and trailing edge curvatures but decline as thickness increases. By analyzing the near-wake structure, we establish that even minimal flow separation increases power consumption while moderate flow separation enhances thrust. Over the range of different-shaped hydrofoils at different

α_{max}

and

ϕ

, maximum propulsion efficiency occurs for those parameters for which there is a small degree of flow separation but with no roll-up of a separating vortex. In comparison, maximum thrust generation occurs when there is a moderately strong flow separation but without induction of a significant amount of fluid around the trailing edge. These insights offer valuable knowledge for understanding fish propulsion efficiency and have applications in designing autonomous underwater vehicles (AUVs) and micro-air vehicles (MAVs). Full article

(This article belongs to the Special Issue Application of CFD Simulations to Marine Hydrodynamic Problems)

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