Research

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23 pages, 9766 KiB

Open AccessArticle

Unmanned Vessel Collision Avoidance Algorithm by Dynamic Window Approach Based on COLREGs Considering the Effects of the Wind and Wave

by Xiaoyu Yuan, Chengchang Tong, Guoxiang He and Hongbo Wang

J. Mar. Sci. Eng. 2023, 11(9), 1831; https://doi.org/10.3390/jmse11091831 - 20 Sep 2023

Cited by 3 | Viewed by 900

Abstract

In recent years, the rapid development of artificial intelligence algorithms has promoted the intelligent transformation of the ship industry; unmanned surface vessels (USVs) have become a widely used representative product. The dynamic window approach (DWA) is an effective robotic collision avoidance algorithm; however, [...] Read more.

In recent years, the rapid development of artificial intelligence algorithms has promoted the intelligent transformation of the ship industry; unmanned surface vessels (USVs) have become a widely used representative product. The dynamic window approach (DWA) is an effective robotic collision avoidance algorithm; however, there are deficiencies in its application to the ship field. First, the DWA algorithm does not consider International Regulations for Preventing Collisions at Sea (COLREGs), which must be met for ship collision avoidance to ensure the navigational safety of the USV and other ships. Second, the DWA algorithm does not consider the influence of wind and waves on the collision avoidance of USVs in actual navigational environments. Reasonable use of windy and wavy environments not only improves navigational safety but also saves navigational time and fuel consumption, thereby improving the economy. Therefore, this paper proposes an improvement algorithm by DWA referred to as utility DWA (UDWA) based on COLREGs considering the sailing environment. The velocity sampling area was improved by dividing the priority, and the velocity function in the objective function was enhanced to convert the effect of wind and waves on the USVs into a change in velocity. The simulation results showed that the UDWA algorithm optimized the distance to the obstacle ship by 43.25%, 31.36%, and 67.81% in a head-on situation, crossing situation, and overtaking situation, respectively, compared to the COLREGs-compliant DWA algorithm, which considers the COLREGs. The improved algorithm not only follows the COLREGs but also has better flexibility in emergency collision avoidance and can safely and economically navigate and complete collision avoidance in windy and wavy environments. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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16 pages, 8422 KiB

Open AccessArticle

Theoretical Analysis Method for Roll Motion of Popup Data Communication Beacons

by Yuanjie Song, Haoyuan Chi, Liang Yu, Chen Wang and Chuan Tian

J. Mar. Sci. Eng. 2023, 11(6), 1193; https://doi.org/10.3390/jmse11061193 - 08 Jun 2023

Viewed by 846

Abstract

The popup data communication beacon (PDCB) can send data to the shore and ships through the BeiDou navigation satellite system (BDS) when it surfaces. The data can be collected by a deep-sea landing vehicle (DSLV) and transmitted using a magnetic induction coil. PDCBs [...] Read more.

The popup data communication beacon (PDCB) can send data to the shore and ships through the BeiDou navigation satellite system (BDS) when it surfaces. The data can be collected by a deep-sea landing vehicle (DSLV) and transmitted using a magnetic induction coil. PDCBs can reduce the cost of DSLV recovery and redeployment. Whether the data can be successfully sent mainly depends on the outlet height and roll angle of the PDCB. Thus, accurately assessing the effect of the roll angle on data transmission is crucial. In this study, first, the differential equation of roll motion was preliminarily established using the small-amplitude wave theory along with the shape characteristics of the PDCB. Next, the nonlinear term of the recovery moment was processed using the Linz Ted Poincaré method. Then, the wave current force was analyzed using the Morrison theoretical formula along with an additional inertia moment calculation formula that is suitable for slender cylindrical small buoys. Finally, the theoretical calculation results were verified using the computational fluid dynamics (CFD) method and pool test. The roll angle error of the theoretical calculation was within 5%. Thus, the heave and roll response of PDCBs can be evaluated using theoretical calculation methods. The proposed calculation formula of additional inertia moment has guiding significance for the further optimization of the structure. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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15 pages, 76418 KiB

Open AccessArticle

MDNet: A Fusion Generative Adversarial Network for Underwater Image Enhancement

by Song Zhang, Shili Zhao, Dong An, Daoliang Li and Ran Zhao

J. Mar. Sci. Eng. 2023, 11(6), 1183; https://doi.org/10.3390/jmse11061183 - 06 Jun 2023

Cited by 2 | Viewed by 1395

Abstract

Underwater images are widely used in ocean resource exploration and ocean environment surveillance. However, due to the influence of light attenuation and noise, underwater images usually display degradation phenomena such as blurring and color deviation; an enhancement method is required to make the [...] Read more.

Underwater images are widely used in ocean resource exploration and ocean environment surveillance. However, due to the influence of light attenuation and noise, underwater images usually display degradation phenomena such as blurring and color deviation; an enhancement method is required to make the images more visible. Currently, there are two major approaches for image enhancement: the traditional methods based on physical or non-physical models, and the deep learning method. Inspired by the fusion-based idea, this paper attempts to combine traditional methods with deep learning and proposes a multi-input dense connection generator network (MDNet) for underwater image enhancement. Raw images and processed images are input into the network together, the shallow information is fully utilized by dense connection, and the network is trained in generative and adversarial manner. We also design a multiple loss function to improve the visual quality of the generated images. We conduct both qualitative and quantitative experiments, and then compare the results with state-of-the-art approaches comprehensively using three representative datasets. Results show that the proposed method can effectively improve the perceptual and statistical quality of underwater images. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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24 pages, 7783 KiB

Open AccessArticle

Two-Phase Flow Pattern Identification by Embedding Double Attention Mechanisms into a Convolutional Neural Network

by Weiliang Qiao, Hongtongyang Guo, Enze Huang, Haiquan Chen and Chuanping Lian

J. Mar. Sci. Eng. 2023, 11(4), 793; https://doi.org/10.3390/jmse11040793 - 06 Apr 2023

Cited by 2 | Viewed by 1352

Abstract

There are inevitable multiphase flow problems in the process of subsea oil-gas acquisition and transportation, of which the two-phase flow involving gas and liquid is given much attention. The performance of pipelines and equipment in subsea systems is greatly affected by various flow [...] Read more.

There are inevitable multiphase flow problems in the process of subsea oil-gas acquisition and transportation, of which the two-phase flow involving gas and liquid is given much attention. The performance of pipelines and equipment in subsea systems is greatly affected by various flow patterns. As a result, correctly and efficiently identifying the flow pattern in a pipeline is critical for the oil and gas industry. In this study, two attention modules, the convolutional block attention module (CBAM) and efficient channel attention (ECA), are introduced into a convolutional neural network (ResNet50) to develop a gas–liquid two-phase flow pattern identification model, which is named CBAM-ECA-ResNet50. To verify the accuracy and efficiency of the proposed model, a collection of gas–liquid two-phase flow pattern images in a vertical pipeline is selected as the dataset, and data augmentation is employed on the training set data to enhance the generalization capability and comprehensive performance of the model. Then, comparison models similar to the proposed model are obtained by adjusting the order and number of the two attention modules in the two positions and by inserting other different attention modules. Afterward, ResNet50 and all proposed models are applied to classify and identify gas–liquid two-phase flow pattern images. As a result, the identification accuracy of the proposed CBAM-ECA-ResNet50 is observed to be the highest (99.62%). In addition, the robustness and complexity of the proposed CBAM-ECA-ResNet50 are satisfactory. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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14 pages, 18013 KiB

Open AccessArticle

A Semantic Segmentation Method Based on Image Entropy Weighted Spatio-Temporal Fusion for Blade Attachment Recognition of Marine Current Turbines

by Fei Qi and Tianzhen Wang

J. Mar. Sci. Eng. 2023, 11(4), 691; https://doi.org/10.3390/jmse11040691 - 24 Mar 2023

Cited by 3 | Viewed by 1120

Abstract

Marine current turbines (MCTs) may exhibit reduced energy production and structural instability due to attachments, such as biofouling and plankton. Semantic segmentation (SS) is utilized to recognize these attachments, enabling on-demand maintenance towards optimizing power generation efficiency and minimizing maintenance costs. However, the [...] Read more.

Marine current turbines (MCTs) may exhibit reduced energy production and structural instability due to attachments, such as biofouling and plankton. Semantic segmentation (SS) is utilized to recognize these attachments, enabling on-demand maintenance towards optimizing power generation efficiency and minimizing maintenance costs. However, the degree of motion blur might vary according to the MCT rotational speed. The SS methods are not robust against such variations, and the recognition accuracy could be significantly reduced. In order to alleviate this problem, the SS method is proposed based on image entropy weighted spatio-temporal fusion (IEWSTF). The method has two features: (1) A spatio-temporal fusion (STF) mechanism is proposed to learn spatio-temporal (ST) features in adjacent frames while conducting feature fusion, thus reducing the impact of motion blur on feature extraction. (2) An image entropy weighting (IEW) mechanism is proposed to adjust the fusion weights adaptively for better fusion effects. The experimental results demonstrate that the proposed method achieves superior recognition performance with MCT datasets with various rotational speeds and is more robust to rotational speed variations than other methods. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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17 pages, 3052 KiB

Open AccessArticle

Techno-Economic Optimal Sizing Design for a Tidal Stream Turbine–Battery System

by Sana Toumi, Yassine Amirat, Elhoussin Elbouchikhi, Zhibin Zhou and Mohamed Benbouzid

J. Mar. Sci. Eng. 2023, 11(3), 679; https://doi.org/10.3390/jmse11030679 - 22 Mar 2023

Viewed by 1415

Abstract

This article deals with the techno-economic optimal sizing of a tidal stream turbine (TST)–battery system. In this study, the TST system consists of a turbine rotor and a permanent magnet synchronous generator (PMSG) associated with a three-phase converter coupled to a DC bus. [...] Read more.

This article deals with the techno-economic optimal sizing of a tidal stream turbine (TST)–battery system. In this study, the TST system consists of a turbine rotor and a permanent magnet synchronous generator (PMSG) associated with a three-phase converter coupled to a DC bus. A battery is used within the system as an energy storage system to absorb excess produced power or cover power deficits. To determine the optimal sizing of the system, an iterative approach was used owing to its ease of implementation, high accuracy, and fast convergence speed, even under environmental constraints such as swell and wave effects. This technique is based on robust energy management, and the recursive algorithm includes the deficiency of power supply probability (DPSP) and the relative excess power generation (REPG) as technical criteria for the system reliability study, and the energy cost (EC) and the total net present cost (TNPC) as economic criteria for the system cost study. As data inputs, the proposed approach used the existing data from the current speed profile, the load, and economic parameters. The desired output is the system component optimal sizing (TST power, and battery capacity). In this paper, the system sizing was studied during a one-year time period to ensure a more reliable and economical system. The results are compared to well-known methods such as genetic algorithms, particle swarm optimization, and software-based (HOMER) approaches. The optimization results confirm the efficiency of the proposed approach in sizing the system, which was simulated using real-world tidal velocity data from a specific deployment site. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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29 pages, 1960 KiB

Open AccessArticle

Autonomous Machinery Management for Supervisory Risk Control Using Particle Swarm Optimization

by Simon Blindheim, Børge Rokseth and Tor Arne Johansen

J. Mar. Sci. Eng. 2023, 11(2), 327; https://doi.org/10.3390/jmse11020327 - 02 Feb 2023

Cited by 4 | Viewed by 1265

Abstract

Safe navigation for maritime autonomous surface ships (MASS) is a challenging task, and generally highly dependent on effective collaboration between multiple sub-systems in environments with various levels of uncertainty. This paper presents a novel methodology combining risk-based optimal control and path following with [...] Read more.

Safe navigation for maritime autonomous surface ships (MASS) is a challenging task, and generally highly dependent on effective collaboration between multiple sub-systems in environments with various levels of uncertainty. This paper presents a novel methodology combining risk-based optimal control and path following with autonomous machinery management (AMM) for MASS navigation and supervisory risk control. Specifically, a risk-aware particle swarm optimization (PSO) scheme utilizes “time-to-grounding” predictions based on weather data and electronic navigational charts (ENC) to simultaneously control both the ship’s motion as well as the machinery system operation (MSO) mode during transit. The proposed autonomous navigation system (ANS) is comprised of an online receding horizon control that uses a PSO approach from previous works, which produces a dynamic risk-aware path with respect to grounding obstacles from a pre-planned MASS path, subsequently given as the input to a line-of-sight guidance controller for path following. Moreover, the MSO mode of the AMM system is simultaneously selected and assigned to explicit segments along the risk-aware path throughout the receding horizon, which effectively introduces into the optimization scheme an additional safety layer as well as another dimension for risk or resource minimization. The performance of the resulting ANS is demonstrated and verified through simulations of a challenging scenario and human assessment of the generated paths. The results show that the optimized paths are more efficient and in line with how human navigators would maneuver a ship close to nearby grounding obstacles, compared to the optimized paths of selected previous works. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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12 pages, 5158 KiB

Open AccessArticle

Design and Experimental Study of Core Bit for Hard Rock Drilling in Deep-Sea

by Xingchen Li, Liang Xiong, Wenwei Xie, Ke Gao, Yutao Shao, Yunlong Chen, Yanjiang Yu, Beibei Kou, Qiuping Lu, Jing Zeng and Haoyu Yu

J. Mar. Sci. Eng. 2023, 11(2), 306; https://doi.org/10.3390/jmse11020306 - 01 Feb 2023

Cited by 2 | Viewed by 2098

Abstract

The hard rock stratum will seriously affect the efficiency of deep-sea drilling and greatly increase the cost of drilling operations due to its complexity. In ocean drilling operations, the design of the bit is critical. Therefore, the core bit should be able to [...] Read more.

The hard rock stratum will seriously affect the efficiency of deep-sea drilling and greatly increase the cost of drilling operations due to its complexity. In ocean drilling operations, the design of the bit is critical. Therefore, the core bit should be able to drill in a variety of formations, especially in hard rock stratum, with the function of reducing the need to change the bit due to formation changes and improving the drilling efficiency. In this paper, three different core bits were designed according to the hard rock stratum of the seabed: the roller bit, diamond bit and bionic bit. According to the test results, it was observed that: (1) It is fully proven that the roller core bit has the characteristics of stable drilling in hard strata, small torque and high drilling efficiency. The same method can realize the core in shallow soft strata through the setting of drilling parameters. (2) For the diamond bit, the field test data show that the new formula diamond bit has a good adaptability to the changing hard rock strata in this area, with an average rate of penetration (ROP) of 4.4 m/h and a bit life of 137.75 m. (3) For the bionic bit, field experiment data showed that drilling in the formation lithology was gray green tuff, which had a core recovery up to 100%. The average ROP was 1.35 m/h, and the highest ROP was 1.88 m/h. The design and experiment of three kinds of drill bits have effectively solved the technical problem of efficient drilling in deep-sea hard-rock stratum. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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22 pages, 6824 KiB

Open AccessArticle

Assessment Method Based on AIS Data Combining the Velocity Obstacle Method and Pareto Selection for the Collision Risk of Inland Ships

by Yan Wang, Yi Zhang, Hengchao Zhao and Hongbo Wang

J. Mar. Sci. Eng. 2022, 10(11), 1723; https://doi.org/10.3390/jmse10111723 - 11 Nov 2022

Cited by 6 | Viewed by 1405

Abstract

A ship collision risk assessment model is an essential part of ship safety navigation. At present, the open water collision risk assessment model (such as the closest point of approach) is applied, but a ship collision risk model suitable for inland rivers is [...] Read more.

A ship collision risk assessment model is an essential part of ship safety navigation. At present, the open water collision risk assessment model (such as the closest point of approach) is applied, but a ship collision risk model suitable for inland rivers is still in the exploration stage. Compared with open waters, the inland waterway has a larger density of ships, and the land and water environments are complex. The existing risk assessment models lack adaptability under the conditions of inland navigation. Therefore, this paper proposes a real-time collision risk assessment method for ships navigating inland rivers. This method utilizes the information of ships’ size in the automatic identification system (AIS) to construct the velocity obstacle cone between convex polygonal targets using the velocity obstacle method. Then, according to the geometric relationship between the relative velocity of two targets and the velocity obstacle cone, a new collision risk assessment model is defined. This model defines two indicators to evaluate the navigation collision risk: the degree of velocity obstacle intrusion (DVOI) and time of velocity obstacle intrusion (TVOI). These two indicators assess the risk of collision, respectively, from two aspects speed and course. In addition, a method using a trajectory compression algorithm to screen collision avoidance operation points in ship AIS trajectory is proposed to screen collision avoidance scenarios in the Yangtze River waterway. The effectiveness of the proposed collision risk model is verified in course-keeping and collision avoidance scenarios and compared with the traditional closest point of approach (CPA) method. The results indicate that the evaluation model for collision risk assessment is more accurate than the CPA method in all scenarios. Finally, this paper uses the Pareto selection algorithm to combine DVOI and TVOI, which can identify the ship that poses the greatest risk to our ship. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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30 pages, 6657 KiB

Open AccessArticle

Effect of Saturation on Shear Behavior and Particle Breakage of Coral Sand

by Xiang Chen, Jianhua Shen, Xing Wang, Ting Yao and Dongsheng Xu

J. Mar. Sci. Eng. 2022, 10(9), 1280; https://doi.org/10.3390/jmse10091280 - 10 Sep 2022

Cited by 12 | Viewed by 1760

Abstract

Coral sand is the main filling material for the island–reef foundation. Under tidal actions, the saturation (Sr) of coral sand layers varies with the specific depths in the reclaimed foundation. Studying the Sr effect of coral sand’s mechanical behaviors is crucial [...] Read more.

Coral sand is the main filling material for the island–reef foundation. Under tidal actions, the saturation (Sr) of coral sand layers varies with the specific depths in the reclaimed foundation. Studying the Sr effect of coral sand’s mechanical behaviors is crucial for the stability of the reclaimed foundation of island–reefs. In this study, a “quantitative injection method” was designed to prepare coral sand with saturation ranging from 90% to 100%, and unconsolidated–undrained (UU) triaxial shear tests were conducted on coral sand under different effective confining pressures (

σ_{3}^{'}

). The results indicated that the stress–strain curves of coral sand under various conditions were of the strain-softening type. When

σ_{3}^{'}

= 200, 400, 600, and 800 kPa, the shear strength of coral sand decreased exponentially by 13.1, 9.1, 16.8, and 15.2%, respectively, with the increase in Sr from 90% to 100%. As Sr rose, the internal friction angle (φ) dropped by 3.77°. The cohesion (c) was not significantly affected by Sr compared to φ. In consideration of the physical susceptibility of coral sand to breakage, relative breakage ratio (B_r) and modified relative breakage index (

B_{r}^{*}

) were introduced to evaluate the particle breakage behaviors of coral sand samples with different Sr levels in the triaxial shear process. It was found that B_r and

B_{r}^{*}

increase linearly with increasing Sr; the effect of Sr on the particle breakage of coral sand weakens significantly when

σ_{3}^{'}

is sufficiently large. The median particle size (d₅₀) of coral sand decreases with increasing Sr, and presents a negative linear correlation with both B_r and

B_{r}^{*}

. Based on comparing the strength and particle breakage characteristics of coral sand samples with varying Sr levels, this study suggests that 92.5% should be considered as the Sr value of coral sand available for testing. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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30 pages, 14084 KiB

Open AccessArticle

Ship Dynamic Positioning Control Based on Active Disturbance Rejection Control

by Hongliang Li, Hao Chen, Ning Gao, Nadia AΪT-Ahmed, Jean-Frederic Charpentier and Mohamed Benbouzid

J. Mar. Sci. Eng. 2022, 10(7), 865; https://doi.org/10.3390/jmse10070865 - 24 Jun 2022

Cited by 6 | Viewed by 2478

Abstract

Nowadays, Dynamic Positioning (DP) is applied to various tasks such as subsea pipeline laying and the requirements for the positioning performance in marine operations are higher and higher. The main objective of this paper is to design a DP controller based on the [...] Read more.

Nowadays, Dynamic Positioning (DP) is applied to various tasks such as subsea pipeline laying and the requirements for the positioning performance in marine operations are higher and higher. The main objective of this paper is to design a DP controller based on the Active Disturbance Rejection Control (ADRC) to solve the problems of long response time, large overshoot and low positioning accuracy in ship positioning. Firstly, the mathematical models of the ship and environmental disturbances are established. Secondly, the basic principle of ADRC is described. Meanwhile, stability analysis of the control system is introduced. Thirdly, ADRC is improved by the fal function filter and phase prediction method which solve the problem of dither and phase delay in tracking differentiators. Finally, simulations are carried out to verify the performance of the designed ADRC and the improved ADRC. Several simulation results show that the designed ADRC can realize the fixed-point control of the ship, which effectively solves the problems of long response time, overshoot and positioning accuracy, and compared with the traditional ADRC, the improved ADRC can reduce the error of straight track control, which indicates that ADRC can meet the requirements for the positioning performance and has a strong application value. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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24 pages, 7056 KiB

Open AccessArticle

Collision-Avoidance Decision System for Inland Ships Based on Velocity Obstacle Algorithms

by Guangyu Zhang, Yan Wang, Jian Liu, Wei Cai and Hongbo Wang

J. Mar. Sci. Eng. 2022, 10(6), 814; https://doi.org/10.3390/jmse10060814 - 14 Jun 2022

Cited by 14 | Viewed by 2102

Abstract

Due to the complex hydrology and narrow channels of inland rivers, ship collision accidents occur frequently. The traditional collision-avoidance algorithms are often aimed at sea areas, and not often at inland rivers. To solve the problem of inland-ship collision avoidance, this paper proposes [...] Read more.

Due to the complex hydrology and narrow channels of inland rivers, ship collision accidents occur frequently. The traditional collision-avoidance algorithms are often aimed at sea areas, and not often at inland rivers. To solve the problem of inland-ship collision avoidance, this paper proposes an inland-ship collision-avoidance decision system based on the velocity obstacle algorithm. The system is designed to assist ships in achieving independent collision-avoidance operations under the limitation of maneuverability while meeting inland-ship collision-avoidance regulations. First, the paper improves the Maneuvering Modeling Group (MMG) model suitable for inland rivers. Then, it improves velocity obstacle algorithms based on the dynamic ship domain, which can deal with different obstacles and three encounter situations (head-on, crossing, and overtaking situations). In addition, this paper proposes a method to deal with close-quarters situations. Finally, the simulation environment built by MATLAB software is used to simulate the collision avoidance of inland ships against different obstacles under different situations with a decision-making time of less than 0.1 s. Through the analysis of the simulation results, the effectiveness and practicability of the system are verified, which can provide reasonable collision-avoidance decisions for inland ships. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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Review

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18 pages, 8363 KiB

Open AccessReview

Influence of Different Static Equilibrium Calculation Methods on the Dynamic Response of Marine Cables during the Releasing Process: Review and a Case Study

by Dapeng Zhang, Bowen Zhao, Jiyuan Sun, Yi Zhang, Keqiang Zhu and Haoyu Jiang

J. Mar. Sci. Eng. 2023, 11(4), 764; https://doi.org/10.3390/jmse11040764 - 31 Mar 2023

Viewed by 1407

Abstract

When analyzing the dynamic characteristics of marine cables, the static equilibrium state must first be calculated; a dynamic analysis can then be carried out based on the static equilibrium. Since the calculation of the static equilibrium is the basis of dynamic calculation, different [...] Read more.

When analyzing the dynamic characteristics of marine cables, the static equilibrium state must first be calculated; a dynamic analysis can then be carried out based on the static equilibrium. Since the calculation of the static equilibrium is the basis of dynamic calculation, different methods for the calculation of the static equilibrium will have important impacts on the dynamic response characteristics of cables, which result in cables having different dynamic characteristics. This paper summarizes the research progress in the effects of different methods for the calculation of the static equilibrium on the dynamic response of marine cables during the releasing process, and current methods for their static calculation are more comprehensively developed as well as being more accurate. To study the influence of different static equilibrium calculation methods, with the reference of some specific parameters of a mooring cable, combined with specific sea conditions, through the necessary simplification of the cable releasing process, based on the lumped mass method, mooring cables are discretized into the lumped mass model, and dynamic analysis models of the releasing process of mooring cables under three methods for the calculation of the static equilibriums (the fast static equilibrium calculation method, the analytic catenary calculation method, and the catenary calculation method) are established. The dynamic characteristics of the spatial configurations of mooring cables based on different static equilibrium calculation methods are obtained through time domain coupling analyses. It was found that if the static equilibrium of a cable is calculated, taking into account gravity, buoyancy, wave current resistance, inertia forces, and the axial stiffness of a cable, then the characteristics of a cable during dynamic descent are closest to that of a real situation. The calculation results have a certain guiding significance for specific engineering practices. Full article

(This article belongs to the Special Issue Young Researchers in Ocean Engineering)

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