CFD Analysis in Ocean Engineering

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Ocean Engineering".

Deadline for manuscript submissions: closed (25 September 2023) | Viewed by 44565

Special Issue Editors

School of Engineering, Design and Built Environment, Western Sydney University, Penrith, NSW, Australia
Interests: fluid–structure interaction; local scour of subsea structures; wave energy; fundamental fluid mechanics
Special Issues, Collections and Topics in MDPI journals
Marine Engineering/College of Engineering, Ocean University of China, Qingdao 266100, China
Interests: CFD; marine propulsion; fluid solid interaction

Special Issue Information

Dear Colleagues,

To accommodate our ever-increasing energy needs, the exploration of oil and natural gas is marching towards the deep sea, and tremendous efforts have been made towards developing viable renewable energy sources from the ocean, including wind, tidal current, and waves. It is utterly important and challenging to guarantee the safety of offshore structures constructed in the ocean for the purpose of extracting resources and energy from the deep sea. Computational Fluid Dynamics (CFD) is playing an increasingly important role in fundamental and applied research in ocean engineering. This special issue aims to collect articles that highlight research in ocean engineering through CFD analysis. It covers a variety of topics, including, but not limited to, wave dynamics, tidal current, offshore fluid-structure interaction, wave and tidal energy, and ship hydrodynamics. Papers that report new research methods, fundamental fluid mechanics, or applied research outcomes in relevant areas are welcome. 

Dr. Ming Zhao
Dr. Qin Zhang
Guest Editors

Manuscript Submission Information

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Keywords

  • waves
  • tidal current
  • vortex-induced vibration
  • flow–structure interaction
  • local scour
  • wave–structure interaction
  • wave energy
  • tidal energy
  • ship hydrodynamics

Published Papers (24 papers)

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Research

31 pages, 48222 KiB  
Article
Investigation of Energy Loss Mechanism and Vortical Structures Characteristics of Marine Sediment Pump Based on the Response Surface Optimization Method
by Guangjie Peng, Yuan Lou, Dehui Yu, Shiming Hong, Guangchao Ji, Lie Ma and Hao Chang
J. Mar. Sci. Eng. 2023, 11(12), 2233; https://doi.org/10.3390/jmse11122233 - 26 Nov 2023
Cited by 1 | Viewed by 815
Abstract
Marine sediment pumps are extensively applied in marine engineering fields with complex media and harsh flow conditions. Therefore, this study conducts a multi-factor optimization design for a marine sediment pump. The response surface optimization method is utilized to improve the efficiency by optimizing [...] Read more.
Marine sediment pumps are extensively applied in marine engineering fields with complex media and harsh flow conditions. Therefore, this study conducts a multi-factor optimization design for a marine sediment pump. The response surface optimization method is utilized to improve the efficiency by optimizing the number of impeller blades, the blade inlet angle, the blade outlet angle, and the blade wrap angle. Next, a response surface regression model is created, and the influence of geometric parameters on the efficiency is determined. Meanwhile, the energy loss mechanism and vortical structure characteristics after optimization are analyzed by applying entropy production and the method for identifying Omega vortices. The findings suggest a 6.33% efficiency enhancement in the optimized model under the design conditions. The impeller’s internal flow field is enhanced, and the entropy generation rate is significantly diminished. The fluid flow adhered more closely to the blade profile, and the velocity and pressure distribution exhibit better uniformity. The presence of large-scale vortices and occurrences of flow separation within the impeller passage experience a notable decrease, and the overall fluid pressure fluctuation amplitude decreased, resulting in a more stable flow. Therefore, the discoveries from the research offer references for the design and selection of marine sediment pumps. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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24 pages, 13719 KiB  
Article
Investigation on the Erosion Characteristics of Liquid–Solid Two-Phase Flow in Tee Pipes Based on CFD-DEM
by Shiming Hong, Guangjie Peng, Dehui Yu, Hao Chang and Xikun Wang
J. Mar. Sci. Eng. 2023, 11(12), 2231; https://doi.org/10.3390/jmse11122231 - 25 Nov 2023
Cited by 1 | Viewed by 850
Abstract
Tee pipes are widely utilized in pipeline transportation, especially in subsea production systems and the chemical industry. The purpose of this research is to study the influences of gravity direction, conveying parameters and particle properties on the erosion distribution in tee junctions. Investigation [...] Read more.
Tee pipes are widely utilized in pipeline transportation, especially in subsea production systems and the chemical industry. The purpose of this research is to study the influences of gravity direction, conveying parameters and particle properties on the erosion distribution in tee junctions. Investigation using the CFD-DEM coupled method is conducted on the flow mechanisms and erosion characteristics in a tee junction under different flow conditions. Firstly, numerical calculations of liquid–solid two-phase flow in a vertical cylindrical pipe are performed, and the comparison between simulation results and experimental results is carried out. Then, the verified lift and erosion models are used for the numerical calculations of tee pipes. Flow mechanisms and erosion characteristics are numerically investigated through analysis of the velocity profiles, streamlines, and erosion contours. The results indicate that the gravity direction has a nonnegligible influence on the cross-sectional velocity profiles, particularly under the condition of high velocity and high particle concentration. The region with the maximum erosion rate occurred at the branch pipes, about three fourths of the pipe diameter away from the tee junction. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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19 pages, 9558 KiB  
Article
Vortex-Induced Vibration and Fatigue Damage Assessment for a Submarine Pipeline on a Sand Wave Seabed
by Xing Zou, Botao Xie, Zhipeng Zang, Enbang Chen and Jing Hou
J. Mar. Sci. Eng. 2023, 11(10), 2031; https://doi.org/10.3390/jmse11102031 - 23 Oct 2023
Cited by 1 | Viewed by 1175
Abstract
Sand waves are commonly formed on the sandy seabed of the continental shelf and characterized by their regular wave-like shape. When a submarine pipeline is laid on this type of seabed, it often experiences free spans due to the unevenness of the seabed. [...] Read more.
Sand waves are commonly formed on the sandy seabed of the continental shelf and characterized by their regular wave-like shape. When a submarine pipeline is laid on this type of seabed, it often experiences free spans due to the unevenness of the seabed. These free spans are particularly vulnerable to vortex-induced vibration (VIV) and the resulting fatigue damage, which have been identified as the primary causes of pipeline failures in offshore oil and gas exploration. This study examines the VIV and fatigue damage of free spans in a submarine pipeline in the Lufeng oilfield, which is located in a large area of sand waves. The assessment conditions encompass the as-laid empty state, the flooded state, and the operational state. Additionally, both the minimum and maximum lay tension are taken into account during the evaluation of VIV and fatigue. The VIV onset screening conducted revealed a considerable number of pipeline free spans exceeding the VIV onset span lengths under both temporary and operating conditions for the non-trench seabed. Furthermore, the analyses indicate that the pipeline does not meet the criteria for VIV fatigue on a non-trenched seabed. Consequently, a proposed solution of implementing a 1 m trench rectification measure for the seabed is recommended. The results demonstrate that this measure effectively mitigates the occurrence of VIV and subsequently reduces fatigue damage across all conditions. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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25 pages, 11712 KiB  
Article
A Numerical Study on the Performance of the 66k DWT Bulk Carrier in Regular and Irregular Waves
by Gu-Hyeon Kim, Seunghyun Hwang, Soon-Hyun Lee, Jun-Hee Lee, Jun Hwangbo, Kwang-Soo Kim and Kwang-Jun Paik
J. Mar. Sci. Eng. 2023, 11(10), 1913; https://doi.org/10.3390/jmse11101913 - 3 Oct 2023
Cited by 2 | Viewed by 869
Abstract
Accurate resistance performance evaluation is essential to predict the minimum propulsion horsepower required for ships in real sea. Therefore, in this paper, the added resistance performance of K-Supramax in various wave conditions was calculated using CFD (Computational Fluid Dynamics). First, to compare the [...] Read more.
Accurate resistance performance evaluation is essential to predict the minimum propulsion horsepower required for ships in real sea. Therefore, in this paper, the added resistance performance of K-Supramax in various wave conditions was calculated using CFD (Computational Fluid Dynamics). First, to compare the resistance performance according to the DOF (Degree of Freedom), the added resistance performance in the head regular wave was investigated and compared with the experiment. The 2DOF and 6DOF results in the head regular wave had no significant differences. Second, to compare the resistance performance among various wave conditions, the effect of the heading angle was analyzed by comparing resistance and motion RAOs (Response Amplitude Operators) in bow quartering sea conditions using 6DOF. The added resistance showed the highest value near the resonance frequency of 170°. As the heading angle increased, the added resistance tended to decrease, regardless of the wavelength ratio. Also, the added resistance performance in irregular waves was investigated with reference to the adverse conditions. The spectral method, which linearly superimposes regular wave results, and the added resistance generated during irregular waves directly through CFD were compared. The resistance in irregular waves increased by approximately 92% for the spectral method and by approximately 72% for the direct irregular wave calculation compared to the resistance in calm water. In addition, the PSD (Power Spectral Density) of resistance and the distribution of motion RAOs obtained from direct irregular wave calculations were investigated. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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27 pages, 8915 KiB  
Article
Numerical Investigation of Self-Propulsion Performance and Noise Level of DARPA Suboff Model
by Chunyu Guo, Xu Wang, Chongge Chen, Yinghong Li and Jian Hu
J. Mar. Sci. Eng. 2023, 11(6), 1206; https://doi.org/10.3390/jmse11061206 - 10 Jun 2023
Cited by 3 | Viewed by 1273
Abstract
Propulsion noise is an enduring problem of significant military and environmental importance. Hence, it is crucial to investigate propeller noise characteristics. In this study, the hydrodynamic performance and noise level of the DARPA (Defense Advanced Research Projects Agency) Suboff submarine with the E1619 [...] Read more.
Propulsion noise is an enduring problem of significant military and environmental importance. Hence, it is crucial to investigate propeller noise characteristics. In this study, the hydrodynamic performance and noise level of the DARPA (Defense Advanced Research Projects Agency) Suboff submarine with the E1619 propeller were analyzed. The hull resistance and propeller hydrodynamics were studied separately, and the numerical results were validated using available experimental values. The self-propulsion point was determined by matching the hull resistance and propeller thrust following ITTC (International Towing Tank Conference) convention. Based on hydrodynamics and acoustic Ffowcs Williams–Hawkings (FW–H) models, the underwater-radiated noise characteristics in the self-propulsion state were simulated. The calculations indicated that the contribution of the quadrupole term in the FW–H equation is not negligible in the high-frequency band. Compared with the noise of open-water propellers, the spectrum of the E1619 propeller in its self-propulsion state is more complex, and the upstream noise is amplified. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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20 pages, 10690 KiB  
Article
Numerical Simulation of Hydrodynamic Performance of Podded Propulsion under Maneuvering Condition
by Weimin Chen, Jiachen Ma, Jian Hu and Li Zhang
J. Mar. Sci. Eng. 2023, 11(4), 874; https://doi.org/10.3390/jmse11040874 - 20 Apr 2023
Cited by 1 | Viewed by 1395
Abstract
Podded propulsion offers excellent maneuverability without the need for mechanically complex transmission systems. However, the hydrodynamic performance of podded propulsion under maneuvering conditions has not yet been adequately investigated. This study proposes a Reynolds-averaged Navier–Stokes (RANS)-based method to investigate the hydrodynamic performance of [...] Read more.
Podded propulsion offers excellent maneuverability without the need for mechanically complex transmission systems. However, the hydrodynamic performance of podded propulsion under maneuvering conditions has not yet been adequately investigated. This study proposes a Reynolds-averaged Navier–Stokes (RANS)-based method to investigate the hydrodynamic performance of pod thrusters under maneuvering conditions. The accuracy of the numerical method is verified based on a comprehensive convergence analysis and experimental comparison. A comparative analysis of the difference in thrust, moment and their coefficients between maneuvering and steady-state conditions is performed. Additionally, the impact of the advance number on the propeller hydrodynamic performance under maneuvering conditions is examined. The results demonstrate that the thrust coefficient and the torque coefficient of the propeller at positive and negative oblique flow angles exhibit asymmetry owing to the influence of the incoming flow velocity. Furthermore, the thrust and torque under maneuvering conditions increase significantly compared with those under the steady-state condition. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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15 pages, 4878 KiB  
Article
Numerical and Experimental Study on NOx Reduction According to the Load in the SCR System of a Marine Boiler
by Jeong-Uk Lee, Sung-Chul Hwang and Seung-Hun Han
J. Mar. Sci. Eng. 2023, 11(4), 777; https://doi.org/10.3390/jmse11040777 - 3 Apr 2023
Cited by 1 | Viewed by 1653
Abstract
Numerical analysis and experimental studies were conducted to evaluate the performance of a selective catalytic reduction (SCR) system according to the load of a 1.5-ton marine boiler. There are post-treatment methods for reducing the exhaust gas emitted from ships, such as low-sulfur oil, [...] Read more.
Numerical analysis and experimental studies were conducted to evaluate the performance of a selective catalytic reduction (SCR) system according to the load of a 1.5-ton marine boiler. There are post-treatment methods for reducing the exhaust gas emitted from ships, such as low-sulfur oil, scrubber, a desulfurization device to remove sulfur oxides (SOx) and particulate matter, an exhaust gas recirculation system, and SCR agents to reduce nitrogen oxides (NOx). Furthermore, there are methods of using eco-friendly natural gas fuels, such as liquefied natural gas (LNG), methanol, liquefied petroleum gas, and ammonia. In the case of LNG, SOx and particulate matter are hardly emitted, and only a small amount of NOx is emitted compared to an internal combustion engine. Therefore, SCR system technology that can remove NOx needs to be applied. As a result of this study, the boiler load increased, and the flow velocity through the outlet decreased. In addition, the NOx emissions of diesel fuel and LNG fuel were reduced by 100% to 0 ppm when the boiler load ratio was 50%. When the load ratio was 75%, the NOx emissions of diesel fuel were reduced by 77.4% to 40 ppm, and those of LNG fuel were reduced by 64.1% to 24 ppm. When the load ratio was 100%, the NOx emissions of diesel fuel were reduced by 66.1% to 60 ppm, and those of LNG fuel were reduced by 47.8% to 24 ppm. In addition, the results of the numerical analysis according to boiler load were almost identical to the experimental results. Finally, this study could design an optimal SCR system through numerical analysis, according to the important parameters of the SCR system. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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28 pages, 13000 KiB  
Article
Thrust Enhancement of DTMB 5415 with Elastic Flapping Foil in Regular Head Waves
by Lei Mei, Wenhui Yan, Junwei Zhou and Weichao Shi
J. Mar. Sci. Eng. 2023, 11(3), 632; https://doi.org/10.3390/jmse11030632 - 17 Mar 2023
Cited by 3 | Viewed by 1751
Abstract
Recent studies indicate that bow foil biomimetic systems can significantly improve ship propulsion in waves. In this paper, the DTMB 5415 ship model is taken as the object and a semi-active elastic flapping foil is proposed to install at its bow underwater position. [...] Read more.
Recent studies indicate that bow foil biomimetic systems can significantly improve ship propulsion in waves. In this paper, the DTMB 5415 ship model is taken as the object and a semi-active elastic flapping foil is proposed to install at its bow underwater position. When a ship sails in head wave, heave and pitch motion will occur, which will drive the bow foil to form heave motion. According to the working characteristics of elastic foil, bow foil can generate forward thrust under drive of given heave motion. At first, co-simulation of the ship with self-pitching bow foil in head waves is realized by ISIS-CFD solver and preliminarily realizes drag reduction and thrust increase effect of the bow foil. At the same time, it is found that the effect of bow foil on hull drag reduction is reflected in two aspects, one is the additional thrust generated by the bow foil and the other is that suppression of the bow foil on hull motion also reduces hull resistance in waves. Then, in order to optimize the working characteristics of elastic bow foil, the influence of spring stiffness and span length of the bow foil on drag reduction and thrust increase effect is discussed. A preliminary spring optimization result is obtained, as well as the influence of the span length of the bow foil on the system. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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17 pages, 4963 KiB  
Article
Enhancement of the Robustness on Advancing Layer Method with Trimmed Hexahedral Volume Mesh for the Generation of the Boundary Layer Grids
by Kwang-Leol Jeong, Sunho Park and Se-Min Jeong
J. Mar. Sci. Eng. 2023, 11(2), 454; https://doi.org/10.3390/jmse11020454 - 18 Feb 2023
Cited by 1 | Viewed by 1556
Abstract
When performing simulations using computational fluid dynamics, the grid systems in the viscous boundary layer regions are important because the velocity and pressure change very rapidly in these regions. Especially for the turbulent flows, thin grids should be arranged densely in the direction [...] Read more.
When performing simulations using computational fluid dynamics, the grid systems in the viscous boundary layer regions are important because the velocity and pressure change very rapidly in these regions. Especially for the turbulent flows, thin grids should be arranged densely in the direction perpendicular to the wall. In this study, the advancing layer method, which has been applied mostly to tetrahedral meshes, is applied to trimmed hexahedral meshes. To generate boundary layer meshes with non-intersecting grid lines near the wall boundaries having concave corners and narrow gaps, the directional vectors of grid lines and faces are smoothed, and the displacement vector fields calculated using the Laplace equation were utilized. Firstly, the details on the newly developed methods are introduced showing simple two-dimensional cases as examples. After applying the methods for a complex three-dimensional geometry to check its applicability and investigating the generated grid systems, the numerical simulations of propeller open water test for INSEAN E779A marine propeller were carried out by simpleFoam, one of the standard solvers of OpenFOAM. The computational results showed good agreement with the experimental results. Therefore, in conclusion, the developed advancing layer method is an appropriate method for generating boundary layer grids of a trimmed hexahedral mesh. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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13 pages, 3702 KiB  
Article
The Analysis of Cavitation Flow and Pressure Pulsation of Bi-Directional Pump
by Haiyu Liu, Fangping Tang, Lijian Shi, Liang Dai, Jie Shen and Jian Liu
J. Mar. Sci. Eng. 2023, 11(2), 268; https://doi.org/10.3390/jmse11020268 - 24 Jan 2023
Cited by 8 | Viewed by 1687
Abstract
A bi-directional pump is designed by using S-shaped hydrofoil, is the most convenient way to achieve bi-directional operation. In this paper, high-speed photography is used to visualize the flow field characteristics of the bidirectional pump under different cavitation numbers, and the flow field [...] Read more.
A bi-directional pump is designed by using S-shaped hydrofoil, is the most convenient way to achieve bi-directional operation. In this paper, high-speed photography is used to visualize the flow field characteristics of the bidirectional pump under different cavitation numbers, and the flow field changes caused by cavitation are quantitatively analyzed in combination with the pressure pulsation sensor. The results show that the operation efficiency of the bidirectional pump in reverse operation is lower than that in forward operation. Tip clearance cavitation occurs on both suction and pressure surfaces of the impeller under reverse operation and large flow. In reverse operation, the influence of guide vane on the main frequency of pressure pulsation in the impeller is obvious. The quasi-periodic vertical cavitation flow phenomenon increases the amplitude of pressure pulsation in the impeller and becomes the main component of the internal flow in the bidirectional axial flow pump. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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14 pages, 5919 KiB  
Article
Numerical Investigations on Scour and Flow around Two Crossing Pipelines on a Sandy Seabed
by Fan Zhang, Zhipeng Zang, Ming Zhao, Jinfeng Zhang, Botao Xie and Xing Zou
J. Mar. Sci. Eng. 2022, 10(12), 2019; https://doi.org/10.3390/jmse10122019 - 17 Dec 2022
Cited by 2 | Viewed by 1598
Abstract
When a pipeline is laid on the seabed, local scour often occurs below it due to sea currents. In practical engineering, there are some cases that two pipelines laid on the seabed need to cross with each other. The complex flow structures around [...] Read more.
When a pipeline is laid on the seabed, local scour often occurs below it due to sea currents. In practical engineering, there are some cases that two pipelines laid on the seabed need to cross with each other. The complex flow structures around two crossing pipelines make the scour characteristics different from that of an isolated single pipeline. In this study, scour below two crossing pipelines was simulated numerically using the CFD software Flow-3D. The study is focused on the effect of the intersecting angle on the equilibrium depth and time scale of scour below the crossing position. Five intersecting angles, i.e., α = 0°, 15°, 30°, 45° and 90°, are considered, where α = 0° and 90° represent two pipelines parallel and perpendicular to each other, respectively. The results show that the equilibrium depth and the time scale of scour below the two crossing pipelines are greater than those of an isolated single pipeline. The equilibrium depth and time scale of scour have the largest values at α = 0° and decrease with the increase of the intersecting angle. Finally, the flow structures around the crossing pipelines are presented to explain the scour process. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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28 pages, 79609 KiB  
Article
Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack
by Jian Wu, Yakun Liu, Di Zhang, Ze Cao and Zijun Guo
J. Mar. Sci. Eng. 2022, 10(12), 1913; https://doi.org/10.3390/jmse10121913 - 5 Dec 2022
Cited by 2 | Viewed by 1450
Abstract
Although flow around a 5:1 rectangular cylinder at small angles of attack (AoA) has been extensively studied, when the AoA becomes larger, the research is rare. Therefore, this study performs Unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) using the k-ω SST turbulence model for unsteady [...] Read more.
Although flow around a 5:1 rectangular cylinder at small angles of attack (AoA) has been extensively studied, when the AoA becomes larger, the research is rare. Therefore, this study performs Unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) using the k-ω SST turbulence model for unsteady flow around a two-dimensional 5:1 rectangular cylinder at different AoAs up to 45°. A strong dependence of the flow characteristics on AoA is observed through the analysis of the time-averaged lift coefficient, drag coefficient, and Strouhal number. The peak of lift and drag coefficient is observed to be correlated, respectively, to the leading- and trailing-edge vortex based on the analysis of the flow. The x′-directional length of the main recirculation bubble on the top side and the distance from the bubble center to the leading edge of the cylinder both reach the maximum when α = 15°. In addition, the standard deviation σx of the time-averaged velocity U¯x along the cylinder shows a trend of increasing at first and then decreasing, and that σy also shows the same trend at α = 20°~45°; it fluctuates within a range of 0.05~0.2 at α = 0°~20°. Finally, two principal modes of vortex shedding are observed with α = 15° being their turning point, (i) “1 + 1” mode: in one vortex shedding period, two major vortices shed off from the top and bottom sides of the cylinder at α ≤ 15°; (ii) “2 + 2” mode, four vortices shed off from the top and bottom sides of the cylinder at α > 15° in one vortex shedding period. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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16 pages, 4223 KiB  
Article
Hydrodynamic Performance of a Floating Offshore Oscillating Water Column Wave Energy Converter
by Mohammad Rashed Mia, Ming Zhao, Helen Wu, Vatsal Dhamelia and Pan Hu
J. Mar. Sci. Eng. 2022, 10(10), 1551; https://doi.org/10.3390/jmse10101551 - 20 Oct 2022
Cited by 3 | Viewed by 2395
Abstract
A floating oscillating water column (OWC) wave energy converter (WEC) supported by mooring lines can be modelled as an elastically supported OWC. The main objective of this paper is to investigate the effects of the frequency ratio on the performance of floating OWC [...] Read more.
A floating oscillating water column (OWC) wave energy converter (WEC) supported by mooring lines can be modelled as an elastically supported OWC. The main objective of this paper is to investigate the effects of the frequency ratio on the performance of floating OWC (oscillating water column) devices that oscillate either vertically or horizontally at two different mass ratios (m = 2 and 3) through two-dimensional computational fluid dynamics simulations. The frequency ratio is the ratio of the natural frequency of the system to the wave frequency. Simulations are conducted for nine frequency ratios in the range between 1 and 10. The hydrodynamic efficiency achieves its maximum at the smallest frequency ratio of 1 if the OWC oscillates horizontally and at the largest frequency ratio of 10 if the OWC oscillates vertically. The frequency ratio affects the hydraulic efficiency of the vertical oscillating OWC significantly stronger than that of the horizontal oscillating OWC, especially when it is small. The air pressure and the volume oscillation in OWC is not affected much by the horizontal motion of the OWC but is significantly affected by the vertical motion, especially at small frequency ratios. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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17 pages, 16802 KiB  
Article
Investigation of Energy Losses Induced by Non-Uniform Inflow in a Coastal Axial-Flow Pump
by Fan Meng, Yanjun Li and Jia Chen
J. Mar. Sci. Eng. 2022, 10(9), 1283; https://doi.org/10.3390/jmse10091283 - 11 Sep 2022
Cited by 3 | Viewed by 1654
Abstract
A non-uniform velocity profile occurs at the inlet of a coastal axial-flow pump which is placed downstream of the forebay with side-intake. As a result, the actual efficiency and head of the pump is dissimilar to the design parameters, and the lack of [...] Read more.
A non-uniform velocity profile occurs at the inlet of a coastal axial-flow pump which is placed downstream of the forebay with side-intake. As a result, the actual efficiency and head of the pump is dissimilar to the design parameters, and the lack of the theoretical investigation on the relationship between inflow distortion and energy losses restricts the application of the coastal axial-flow pump in the drainage project. In this paper, the unsteady numerical simulation and entropy production theory are employed to obtain the internal flow structure and quantify energy losses, respectively, with three inflow deflection angles (θ = 0°, 15°, or 30°). It is reported that the best efficiency point (BEP) shifts to large flow rate with θ increasing, due to the decline of the velocity component in axial direction at the impeller inlet. Therefore, the total entropy production (TEP) of the coastal axial-flow pump rises with θ increasing under small flow rates, but it decreases with θ increasing under large flow rates. The high total entropy production rate (TEPR) in the vicinity of the tailing edge of the impeller and guide vanes rises with θ increasing, caused by the enhanced wake vortex strength. In addition, the high TEPR area near the inlet of outflow conduit rises with θ increasing, originated from the improvement of secondary vortices intensity. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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21 pages, 11487 KiB  
Article
CFD Method to Study Hydrodynamics Forces Acting on Ship Navigating in Confined Curved Channels with Current
by Bo Yang, Sami Kaidi and Emmanuel Lefrançois
J. Mar. Sci. Eng. 2022, 10(9), 1263; https://doi.org/10.3390/jmse10091263 - 7 Sep 2022
Cited by 1 | Viewed by 1604
Abstract
The bending section of the restricted channel is one of the most accident-prone areas for inland ships, but few clear investigations on the curvature effect have been conducted till now. Therefore, this paper presents numerical research of the curvature effect in confined bending [...] Read more.
The bending section of the restricted channel is one of the most accident-prone areas for inland ships, but few clear investigations on the curvature effect have been conducted till now. Therefore, this paper presents numerical research of the curvature effect in confined bending channels on ship hydrodynamics. The unsteady Navier–Stokes equations closed by the realizable K-Epsilon turbulence model are utilized to simulate the flow around a three-dimensional inland ship. A mesh verification analysis is performed to select the most suitable grid size, and the CFD model is validated in a regular confined channel by comparing the numerical resistance forces with those from experiments. The impacts of the channel slope angle, channel radius, ship type (ship length), and current velocity in curved channels on ship hydrodynamics are studied with their influence patterns and mechanisms being analyzed in detail. Results show that channel radius only affects the yaw moment much, whereas ship hydrodynamics are greatly sensitive to the slope angle only when the angle is below a certain threshold value. Compared with short ships, much stronger spiral currents can be noticed passing through long ships in the same channel configuration. Current velocity affects both resistance and yaw moment a lot, with a critical current velocity for sway force. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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21 pages, 9985 KiB  
Article
Three-Dimensional Direct Numerical Simulations of a Yawed Square Cylinder in Steady Flow
by Xiaofan Lou, Chenlin Sun, Hongyi Jiang, Hongjun Zhu, Hongwei An and Tongming Zhou
J. Mar. Sci. Eng. 2022, 10(8), 1128; https://doi.org/10.3390/jmse10081128 - 17 Aug 2022
Cited by 1 | Viewed by 1497
Abstract
The effects of yaw angle on wake characteristics of a stationary square cylinder were investigated in terms of the hydrodynamic forces, the vortex shedding frequency, and the vortical structures using direct numerical simulations (DNS) at a Reynolds number of 1000. In total, four [...] Read more.
The effects of yaw angle on wake characteristics of a stationary square cylinder were investigated in terms of the hydrodynamic forces, the vortex shedding frequency, and the vortical structures using direct numerical simulations (DNS) at a Reynolds number of 1000. In total, four yaw angles, namely, α = 0°, 15°, 30°, and 45°, were considered. The three-dimensional (3D) Navier–Stokes equations were solved directly using the finite volume method in OpenFOAM. It was found that the first-order statistics of the drag coefficient and the Strouhal number satisfied the independence principle (IP) closely. However, the second-order statistics of the drag and lift coefficients deviated apparently from the IP for α ≥ 25°. The iso-surfaces of the spanwise vorticity gradually disorganized and the magnitudes of the spanwise vorticity contour decreased as the yaw angle α was increased from 0° to 45°. By contrast, the streamwise vorticity iso-surfaces were found to become more organized and the magnitudes of the spanwise velocity contour became larger as a result of the increase in yaw angle, indicating the impairment of the quasi-two-dimensionality and the enhancement of the three-dimensionality of the wake flow. Extensive comparisons were also made with previous DNS results for a yawed circular cylinder, and both similarities and differences between these two kinds of cylinder wakes are discussed. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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26 pages, 17904 KiB  
Article
Spectral Analysis of Flow around Single and Two Crossing Circular Cylinders Arranged at 60 and 90 Degrees
by Tianyuan Wang, Qingqing Yang, Yeting Tang, Hongda Shi, Qin Zhang, Mengfei Wang, Andrey Epikhin and Andrey Britov
J. Mar. Sci. Eng. 2022, 10(6), 811; https://doi.org/10.3390/jmse10060811 - 14 Jun 2022
Cited by 3 | Viewed by 1747
Abstract
Two modal decomposition techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD), were used to identify the wake patterns past single and two crossing cylinders in 60° and 90° arrangements with gap ratio G = 4. The flow was simulated using [...] Read more.
Two modal decomposition techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD), were used to identify the wake patterns past single and two crossing cylinders in 60° and 90° arrangements with gap ratio G = 4. The flow was simulated using direct numerical simulations (DNS) for Reynolds numbers Re = 100. From modal analysis, the flow’s spatial scale decreased with increasing modal frequency. Two main modes were identified in the wake of the cylinders, namely spatially antisymmetric and symmetric modes. Antisymmetric and symmetric modes were related to the cylinders’ vortex shedding and shedding vortices’ shift motion, respectively, whose frequencies were odd and even multiples of the cylinders’ lift force frequency. In addition, a low-frequency mode concerning the shadowing effect of the downstream cylinder (DC) in 90° arrangement was found in the wake of the DC centre. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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19 pages, 9502 KiB  
Article
Hydrodynamic Forces and Wake Distribution of Various Ship Shapes Calculated Using a Reynolds Stress Model
by Satoshi Matsuda and Tokihiro Katsui
J. Mar. Sci. Eng. 2022, 10(6), 777; https://doi.org/10.3390/jmse10060777 - 3 Jun 2022
Cited by 4 | Viewed by 1952
Abstract
The Reynolds-averaged Navier–Stokes (RANS)-based computational fluid dynamics (CFD) calculation using a two-equation turbulence model, such as the k–omega shear-stress transport (SST) model, is a mainstream method with sufficient accuracy for the estimation of integral hydrodynamic forces and moment at both the model-scale [...] Read more.
The Reynolds-averaged Navier–Stokes (RANS)-based computational fluid dynamics (CFD) calculation using a two-equation turbulence model, such as the k–omega shear-stress transport (SST) model, is a mainstream method with sufficient accuracy for the estimation of integral hydrodynamic forces and moment at both the model-scale and full scale. This paper confirmed that the Reynolds stress model (RSM) has sufficient estimation accuracy of viscous resistance and wake distribution at the hull design stage. Herein, the ability of RSMs to estimate the viscous resistance and wake distribution of a JBC ship is evaluated. Specifically, the verification and validation (V&V) method is employed to indicate the numerical and model uncertainties of each turbulence model used to estimate the viscous resistance. The RSMs showed higher numerical uncertainty than the k–omega SST. However, the uncertainty of the experimental measurements is generally smaller than the numerical uncertainty. Moreover, the linear pressure–strain (LPS) and the linear pressure–strain two-layer (LPST) models show less comparison error of the viscous resistance than the k–omega SST. Furthermore, the LPST and k–omega SST models are applied to twenty ships with various full and fine hull forms to calculate the viscous resistance and compare it with the experimental results. The viscous resistance of the LPST model showed a small difference when employed in experimental fluid dynamics (EFD) and CFD calculations. Using the LPST model, the viscous resistance can be estimated with high accuracy in our setting. For industrial use, this study could provide an important insight into the designing of various types of vessels. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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21 pages, 12861 KiB  
Article
Numerical Investigation of the Vibration of a Circular Cylinder in Oscillatory Flow in Oblique Directions
by Erfan Taheri, Ming Zhao and Helen Wu
J. Mar. Sci. Eng. 2022, 10(6), 767; https://doi.org/10.3390/jmse10060767 - 1 Jun 2022
Cited by 6 | Viewed by 1815
Abstract
The response of an elastically mounted circular cylinder vibrating in an oscillatory flow oblique to the flow direction is investigated. Simulations are conducted for vibration angles ranging from 0° to 90°, with 0° and 90° corresponding to the cases where the vibration is [...] Read more.
The response of an elastically mounted circular cylinder vibrating in an oscillatory flow oblique to the flow direction is investigated. Simulations are conducted for vibration angles ranging from 0° to 90°, with 0° and 90° corresponding to the cases where the vibration is inline and perpendicular to the flow direction, respectively. One mass ratio of 2, one Reynolds number of 150, and two Keulegan–Carpenter (KC) numbers of 5 and 10 and a wide range of frequency ratios that cover the lock-in regime are considered. The frequency ratio is the ratio of the oscillatory flow frequency to the natural frequency. The maximum vibration amplitude is highest when the cylinder vibrates in the flow direction (vibration angle = 0°) and gradually decreases with the increase of the vibration direction. All the identified flow regimes are mapped on the frequency ratio versus vibration angle space. In addition to the flow regimes that exist for a stationary cylinder, two variants of Regime F (F1 and F2), a new flow regime R and an unstable regime D/F are found. The vortex street directions of Regime F1 and F2 are the opposite to and the same as the direction of the vibration, respectively, Regime R is a regime where a dominant vortex circles around the cylinder and Regime D/F is an unstable regime where the flow changes between Regime D and F frequently. The contribution of the higher harmonics in the vibration increases with the increase of the vibration direction angle. As a result of the strong contribution of higher harmonics at large vibration angles and small frequency ratios, local peak values of the vibration amplitude are found at frequency ratios of 0.4 and 0.25 for KC = 5 and 10, respectively. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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26 pages, 10516 KiB  
Article
Research on Optimization Design of Fully Parameterized Pump-Jet Propulsion
by Chunxiao Wu, Yu Lu, Shewen Liu, Zhiyuan Li, Zhuhao Gu, Wu Shao and Chuang Li
J. Mar. Sci. Eng. 2022, 10(6), 766; https://doi.org/10.3390/jmse10060766 - 1 Jun 2022
Cited by 2 | Viewed by 1923
Abstract
A pump-jet propulsion system is composed of rotor, stator, and duct. The stator has the front stator type and the rear stator type; the conduit also has the acceleration conduit and the deceleration conduit two forms. It is difficult to design and evaluate [...] Read more.
A pump-jet propulsion system is composed of rotor, stator, and duct. The stator has the front stator type and the rear stator type; the conduit also has the acceleration conduit and the deceleration conduit two forms. It is difficult to design and evaluate the performance of a pump-jet propulsion system because of its complex structure and many changes in component parameters. Due to the limitation of time and cost in the design process of the pump-jet propulsion system, it is difficult to find the optimal scheme in the design space. However, under the guidance of an optimization algorithm, the automatic optimization method can fill the design space with a large number of design schemes. In this paper, the geometry reconstruction technique, hydraulic performance evaluation technique and optimization technique of the pump-jet propulsion system are combined to realize the automation of the whole design process. Firstly, the geometric modeling of the pump-jet propulsion system is completed by a full parametric modeling method, and then the hydrodynamic performance of the pump-jet propulsion system is calculated based on the numerical simulation technique. The radial parameters in the fully parametric configuration of the pump-jet propulsion system were selected as the optimization design variables, and the hydro-dynamic performance was optimized as the objective function. Finally, the pump-jet propulsion system optimization design system was constructed by using the global intelligent optimization algorithm. This study provides a theoretical basis and technical guidance for numerical calculation and configuration optimization design of pump-jet propulsion system. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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16 pages, 2212 KiB  
Article
The Force Exerted by Surface Wave on Cylinder and Its Parameterization: Morison Equation Revisited
by Xiaoxiao Zan, Zhenhua Lin and Ying Gou
J. Mar. Sci. Eng. 2022, 10(5), 702; https://doi.org/10.3390/jmse10050702 - 20 May 2022
Cited by 1 | Viewed by 2364
Abstract
The Morison equation is widely used to estimate the loads by surface waves on cylinders. The formulation and coefficients determination method of the original work by Morison et al. are revisited, it is found that there exist some issues yet to be explained, [...] Read more.
The Morison equation is widely used to estimate the loads by surface waves on cylinders. The formulation and coefficients determination method of the original work by Morison et al. are revisited, it is found that there exist some issues yet to be explained, e.g., the larger uncertainties in drag coefficient and the underestimated maximum moments. Numerical simulation with a similar configuration is used to reproduce these issues and the results help discover the reason and mechanism for these phenomena. The analysis shows that the larger uncertainties in drag coefficient are caused by the introduction of linear wave theory, which is used to derive the velocity and acceleration at cylinder location as direct measurements are not available. The results also show that the underestimation of maximum moments is induced by the wave run-up process, which is neglected in the Morison equation. The scale of wave run-up is approximately the length of cylinder diameter. The results indicate although most recent studies are focusing on the high-frequency loads on cylinders by nonlinear waves, there still exist some issues to be resolved in the linear wave regime. Further studies are required to parameterize the additional loads by wave run-up to strengthen the robustness of the Morison equation. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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17 pages, 5126 KiB  
Article
Control of Flow Past a Circular Cylinder Using a Rotating Control Rod
by Ming Zhao and Erfan Taheri
J. Mar. Sci. Eng. 2022, 10(5), 608; https://doi.org/10.3390/jmse10050608 - 29 Apr 2022
Cited by 5 | Viewed by 2306
Abstract
Control of flow past a circular cylinder using a rotating control rod is investigated by conducting two-dimensional numerical simulations with a Reynolds number of 200, a rod-to-cylinder diameter ratio of 0.2, a gap ratio of 0.2, position angles of the control rod between [...] Read more.
Control of flow past a circular cylinder using a rotating control rod is investigated by conducting two-dimensional numerical simulations with a Reynolds number of 200, a rod-to-cylinder diameter ratio of 0.2, a gap ratio of 0.2, position angles of the control rod between 0° and 180°, and rotation rates between −7 and 7. The rotation rate is positive if the cylinder rotates in the anticlockwise direction. The aim of this paper is to discover the effects of the position angle and the rotation rate on flow control. If the rod is placed at the side (position angle = 90°) or nearly to the side of the cylinder (position angle = 45° and 135°), the rotating rod affects the flow in three ways, depending on its rotation rate: (1) strong negative rotation of the rod weakens the negative free shear layers and reduces the lift; (2) flow through the gap interferes with vortex shedding when the rotation rate is small in either direction; and (3) strong positive rotation of the rod enhances the negative free shear layers and increases the lift coefficient. Placing a rotation rod immediately in front of or behind the cylinder (position angle = 0° or 180°) causes a reduction in the lift coefficient for all rotation rates. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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15 pages, 6806 KiB  
Article
Concept and Performance Analysis of Propulsion Units Intended for Distributed Ship Systems
by Ladislav Illes, Martin Jurkovic, Tomas Kalina, Jarmila Sosedova, Piotr Gorzelanczyk, Ondrej Stopka and Tibor Kubjatko
J. Mar. Sci. Eng. 2022, 10(4), 448; https://doi.org/10.3390/jmse10040448 - 22 Mar 2022
Cited by 3 | Viewed by 2048
Abstract
Limited navigation depth, especially on inland waterways, is one of the main limiting factors that shorten the navigation period. Distributed propulsion systems represent an opportunity to increase the navigability of ships across critical sections of waterways characterized by limited navigation depth. In the [...] Read more.
Limited navigation depth, especially on inland waterways, is one of the main limiting factors that shorten the navigation period. Distributed propulsion systems represent an opportunity to increase the navigability of ships across critical sections of waterways characterized by limited navigation depth. In the case of distributed propulsion systems, it is necessary to examine the position of the propellers and their efficiency, suitable design, and interaction with the surroundings. In this study, self-propelled propulsion units located on the side of the ship are investigated at the level of computational fluid dynamics (CFD) analyses. Seven different types of ducts are considered for the proposed propeller geometry in order to ensure the necessary water supply, to prevent air intake, and to ensure high performance in the serial arrangement of propulsors on the side of the hull. Comparative analyses have shown that propulsion units with Ducts 5 and 6 have sufficient resistance to ventilation at a limited depth and deliver acceptable performance at low inflow and outflow rates. This feature is important in serial configurations, which confirms previous research on this issue. Performance can be further increased by reducing the duct resistance at higher speeds. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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29 pages, 92385 KiB  
Article
CFD Research on the Hydrodynamic Performance of Submarine Sailing near the Free Surface with Long-Crested Waves
by Kai Dong, Xianzhou Wang, Donglei Zhang, Liwei Liu and Dakui Feng
J. Mar. Sci. Eng. 2022, 10(1), 90; https://doi.org/10.3390/jmse10010090 - 10 Jan 2022
Cited by 7 | Viewed by 2960
Abstract
The simulations of submarine sailing near the free surface with long-crested waves have been conducted in this study using an in-house viscous URANS solver with an overset grid approach. First, the verification and validation procedures were performed to evaluate the reliability, with the [...] Read more.
The simulations of submarine sailing near the free surface with long-crested waves have been conducted in this study using an in-house viscous URANS solver with an overset grid approach. First, the verification and validation procedures were performed to evaluate the reliability, with the results showing that the generation of irregular waves is adequately accurate and the results of total resistance are in good agreement with EFD. Next, three different submerged depths ranging from 1.1D to 3.3D were selected and the corresponding conditions of submarine sailing near calm water were simulated, the results of which were then compared with each other to investigate the influence of irregular waves and submerged depths. The simulations of the model near calm water at different submerged depths demonstrated that the free surface will cause increasing resistance, lift, and bow-up moments of the model, and this influence decreases dramatically with greater submerged depths. The results of the irregular wave simulations showed that irregular waves cause considerable fluctuations of hydrodynamic force and moments, and that this influence remains even at a deeper submerged depth, which can complicate the control strategies of the submarine. The response spectrum of hydrodynamic forces and moments showed slight amplitudes in the high-frequency region, and the model showed less sensitivity to high-frequency excitations. Full article
(This article belongs to the Special Issue CFD Analysis in Ocean Engineering)
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