Journal of Marine Science and Engineering

Research

15 pages, 6673 KiB

Open AccessArticle

Optimum Arrangement Design of Mastic Ropes for Membrane-Type LNG Tanks Considering the Flatness of Thermal Insulation Panel and Production Cost

by Do-Hyun Chun, Myung-Il Roh and Seung-Ho Ham

J. Mar. Sci. Eng. 2020, 8(5), 353; https://doi.org/10.3390/jmse8050353 - 16 May 2020

Cited by 4 | Viewed by 3030

Abstract

Thermal insulation panels are installed on the inner walls of liquefied natural gas (LNG) tanks of an LNG carrier to maintain the cryogenic temperature. Mastic ropes are used to attach thermal insulation panels to the inner walls and to fill the gap between [...] Read more.

Thermal insulation panels are installed on the inner walls of liquefied natural gas (LNG) tanks of an LNG carrier to maintain the cryogenic temperature. Mastic ropes are used to attach thermal insulation panels to the inner walls and to fill the gap between the walls and panels. Because the inner walls of the LNG tanks can be corrugated owing to production errors, a large amount of mastic ropes are required to maintain the flatness of the thermal insulation panels. Therefore, in this study, an optimization method is proposed to minimize the total amount of mastic ropes for satisfying the flatness criterion of thermal insulation panels. For this purpose, an optimization problem is mathematically formulated. An objective function is used to minimize the total amount of mastic ropes considering constraints to flatten the thermal insulation panels. This function is applied to the design of membrane-type LNG tanks to verify the effectiveness and feasibility of the proposed method. Consequently, we confirm that the proposed method can provide a more effective arrangement design of mastic ropes compared with manual design. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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31 pages, 4446 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Design and Analysis of a Variable Buoyancy System for Efficient Hovering Control of Underwater Vehicles with State Feedback Controller

by Brij Kishor Tiwari and Rajiv Sharma

J. Mar. Sci. Eng. 2020, 8(4), 263; https://doi.org/10.3390/jmse8040263 - 08 Apr 2020

Cited by 22 | Viewed by 6480

Abstract

The design process for Variable Buoyancy System (VBS) is not known in full, and existing approaches are not scalable. Furthermore, almost all the small size Autonomous Underwater Vehicles/Gliders (AUVs/G’s) use very low capacity of buoyancy change (in the range of few milliliters) and [...] Read more.

The design process for Variable Buoyancy System (VBS) is not known in full, and existing approaches are not scalable. Furthermore, almost all the small size Autonomous Underwater Vehicles/Gliders (AUVs/G’s) use very low capacity of buoyancy change (in the range of few milliliters) and the large size AUVs require large buoyancy change. Especially for adverse weather conditions, emergency recovery or defense-related applications, higher rate of rising/sinking (heave velocity) is needed along with an ability to hover at certain depth of operation. Depth of UVs can be controlled either by changing the displaced volume or by changing the overall weight and, herein, our focus is on the later. This article presents the problem of design and analysis of VBS for efficient hovering control of underwater vehicles at desired depth using the state feedback controller. We formulate and analyze the design and analysis approach of VBS using the fundamental of mechanics, system dynamics integration and control theory. Buoyancy is controlled by changing the overall weight of the vehicle using the ballasting/de-ballasting of water in ballast tanks through the use of Positive Displacement Pump (PDP) for control in heave velocity and hovering depth. Furthermore, detailed mass metric analysis of scalable design of VBS for different buoyancy capacities is performed to analyze the overall performance of the VBS. Also, the performances of AUVs integrated with VBS of different buoyancy capacities are investigated in both the open loop and closed loop with the LQR state feedback controller. Hovering performance results are presented for three Design Examples (DEs) of AUVs with 2.8 m, 4.0 m and 5.0 m length and they are integrated with various buoyancy capacities at 9 kg/min rate of change of buoyancy. Results indicate that the AUVs achieve the desired depth with almost negligible steady state error and when they reach the desired hovering depth of 400 m the maximum pitch angle achieved of 16.5 degree for all the Des is observed. Maximum heave velocity achieved during sinking is 0.44 m/s and it reduces to zero when the vehicle reaches the desired depth of hovering. The presented computer simulation results indicate good performance and demonstrate that the designed VBS is effective and efficient in changing the buoyancy, controlling and maintaining the depth, controlling the heave velocity and can be used in rescue/attack operations of both the civil and defense UVs. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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20 pages, 10885 KiB

Open AccessArticle

A Stereolithographic Model-Based Dense Body Plan Generation Method to Construct a Ship Hydrodynamic Coefficients Database

by Qianfeng Jing, Helong Shen and Yong Yin

J. Mar. Sci. Eng. 2020, 8(3), 222; https://doi.org/10.3390/jmse8030222 - 21 Mar 2020

Cited by 3 | Viewed by 4147

Abstract

A ship’s body plan is a vital data resource of ship hydrodynamics analysis, especially for time-domain simulations. Motivated by 3D printing technology, a novel dense body plan generation method is developed in this study. The slicing algorithm is adopted to generate dense 2D [...] Read more.

A ship’s body plan is a vital data resource of ship hydrodynamics analysis, especially for time-domain simulations. Motivated by 3D printing technology, a novel dense body plan generation method is developed in this study. The slicing algorithm is adopted to generate dense 2D body plans from ship stereolithographic models. The dense body plan can be produced automatically under arbitrary rotational angles and slices. Moreover, a section redistribution algorithm is integrated to eliminate the non-uniform distribution features in sliced data inherited from the stereolithographic models. The benchmark ship models are selected to validate the accuracy of the method. The hull volumes of three ship models are calculated based on the produced data. The calculated results show satisfactory agreement with the published values. Furthermore, the estimation formulas of wetted surface area (WSA) are reviewed and utilized for validation. The calculated WSAs by slice integration turn out to be adaptive and accurate. The time costs of different slices are provided to illustrate the computational efficiency. A ship hydrodynamic coefficients database is constructed based on a 2D strip method and the produced data. The proposed method aims to improve the generation process of the body plan, which could meet the accuracy requirements of the strip method. As a result, hydrodynamic coefficients utilized in time-domain simulations could be obtained smoothly from the database. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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19 pages, 5942 KiB

Open AccessArticle

Effects of Design Factors on Drag Forces and Deformations on Marine Aquaculture Cages: A Parametric Study Based on Numerical Simulations

by Shuchuang Dong, Xinxing You and Fuxiang Hu

J. Mar. Sci. Eng. 2020, 8(2), 125; https://doi.org/10.3390/jmse8020125 - 16 Feb 2020

Cited by 13 | Viewed by 4239

Abstract

In Japan, the marine aquaculture net cage has an important role in farming pacific bluefin tuna farming in oceans, and the design of the net cage needs to ensure robustness against hostile oceanic conditions. Accordingly, this study focuses on the drag forces and [...] Read more.

In Japan, the marine aquaculture net cage has an important role in farming pacific bluefin tuna farming in oceans, and the design of the net cage needs to ensure robustness against hostile oceanic conditions. Accordingly, this study focuses on the drag forces and the cage volume of the net cage, and on their variations induced by different design parameters (netting solidity ratio, netting height, and bottom weight). A series of parametric studies on drag force and deformation of the net cage was conducted using a numerical simulation model. Accordingly, the contribution of each parameter to the drag and volume was analyzed using a generalized additive model. The results indicate that the bottom weight had the highest contribution to the holding ratio of the cage volume, whereas the netting height had the highest contribution to the drag coefficient of the net cage. Finally, a fast prediction model was created by a backpropagation (BP) neural network model and was examined for the accurate prediction of the objective variables. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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19 pages, 12385 KiB

Open AccessArticle

Numerical Study on Hydrodynamic Responses of Floating Rope Enclosure in Waves and Currents

by Hui Yang, Yun-Peng Zhao, Chun-Wei Bi and Yong Cui

J. Mar. Sci. Eng. 2020, 8(2), 82; https://doi.org/10.3390/jmse8020082 - 26 Jan 2020

Cited by 7 | Viewed by 2584

Abstract

Enclosure aquaculture is a healthy and ecological aquaculture pattern developed in recent years to relieve the pressure due to the wild fish stock decline and water pollution. The object of this paper was a floating rope enclosure, which mainly consisted of floaters, mooring [...] Read more.

Enclosure aquaculture is a healthy and ecological aquaculture pattern developed in recent years to relieve the pressure due to the wild fish stock decline and water pollution. The object of this paper was a floating rope enclosure, which mainly consisted of floaters, mooring lines, sinkers and a net. In order to optimize mooring design factors, the hydrodynamic responses of the floating rope enclosure with different mooring systems in combined wave-current were investigated by experimental and numerical methods. Physical model experiments with a model scale of 1:50 were performed to investigate the hydrodynamic characteristics of a floating rope enclosure with 12 mooring lines. Based on the lumped mass method, the numerical model was established to investigate the effects of mooring design factors on the mooring line tension, force acting on the bottom, and the volume retention of the floating rope enclosure. Through the analysis of numerical and experimental results, it was found that the maximum mooring line tension of the floating rope enclosure occurs on both sides of the windward. Increasing the number of mooring lines on the windward side is helpful to reduce the maximum mooring line tension. Waves and current both have an influence on the mooring line tension; in contrast, currents have a more obvious effect on the mooring line tension than waves. However, the influence of the wave period on the maximum mooring line tension is small. The force endured by the bottom of the floating rope enclosure also changes periodically with the wave period. Yet, the maximum force endured by the bottom of floating rope enclosure occurred at the windward and leeward of the structure. The volume retention of the floating rope enclosure increased with the increasing amount of mooring lines. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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22 pages, 3570 KiB

Open AccessArticle

Numerical Analysis of Sandwich Composite Deep Submarine Pressure Hull Considering Failure Criteria

by Mahmoud Helal, Huinan Huang, Defu Wang and Elsayed Fathallah

J. Mar. Sci. Eng. 2019, 7(10), 377; https://doi.org/10.3390/jmse7100377 - 22 Oct 2019

Cited by 14 | Viewed by 4735

Abstract

The pressure hull is the primary element of submarine, which withstands diving pressure and provides essential capacity for electronic systems and buoyancy. This study presents a numerical analysis and design optimization of sandwich composite deep submarine pressure hull using finite element modeling technique. [...] Read more.

The pressure hull is the primary element of submarine, which withstands diving pressure and provides essential capacity for electronic systems and buoyancy. This study presents a numerical analysis and design optimization of sandwich composite deep submarine pressure hull using finite element modeling technique. This study aims to minimize buoyancy factor and maximize deck area and buckling strength factors. The collapse depth is taken as a base in the pressure hull design. The pressure hull has been analyzed using two composite materials, T700/Epoxy and B(4)5505/Epoxy, to form the upper and lower faces of the sandwich composite deep submarine pressure hull. The laminated control surface is optimized for the first ply failure index (FI) considering both Tsai–Wu and maximum stress failure criteria. The results obtained emphasize an important fact that the presence of core layer in sandwich composite pressure hull is not always more efficient. The use of sandwich in the design of composite deep submarine pressure hull at extreme depths is not a safe option. Additionally, the core thickness plays a minor role in the design of composite deep submarine pressure hull. The outcome of an optimization at extreme depths illustrates that the upper and lower faces become thicker and the core thickness becomes thinner. However, at shallow-to-moderate depths, it is recommended to use sandwich composite with a thick core to resist the shell buckling of composite submarine pressure hull. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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14 pages, 6834 KiB

Open AccessArticle

Strength Performance of an Eccentric Jacket Substructure

by Xiaoshuang Han, Anlong Chen, Bo Zhou, Guiyong Zhang and Wie Min Gho

J. Mar. Sci. Eng. 2019, 7(8), 264; https://doi.org/10.3390/jmse7080264 - 10 Aug 2019

Cited by 2 | Viewed by 2805

Abstract

An eccentric jacket substructure is comprised of circular hollow section tubular joints with complete overlap of braces. The joint is formed with the lap brace overlapping the diagonal through the brace joining the chord face. In this study, the jacket substructure is subjected [...] Read more.

An eccentric jacket substructure is comprised of circular hollow section tubular joints with complete overlap of braces. The joint is formed with the lap brace overlapping the diagonal through the brace joining the chord face. In this study, the jacket substructure is subjected to a static vertical load due to self-weight and facilities, and four horizontal loads to simulate the environmental loads applied at four different horizontal angles. The maximum stresses at each level of the eccentric jacket are found lower than that of the traditional jacket. For the eccentric jacket substructure, the high stress critical area is mostly located at the short segment of the diagonal through brace joining the chord face. From the parametric study, the ultimate strength of the joint with the complete overlap of braces of the eccentric jacket reduces with increasing the gap size-to-through brace diameter ratio, ξ. With the short segment of the through-brace joining the chord face, the high-stress area is transferred from the joint intersection of the chord and the braces to the lap brace and the diagonal through-brace. It could; therefore, be concluded, based on the strength performance, that the eccentric jacket performed better with maximum stresses and high-stress critical areas. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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9 pages, 1095 KiB

Open AccessArticle

Prediction of Grouting Penetration Height Along the Shaft of Base Grouted Pile

by Kai Fang, Tongbin Zhao, Yunliang Tan and Yue Qiu

J. Mar. Sci. Eng. 2019, 7(7), 212; https://doi.org/10.3390/jmse7070212 - 10 Jul 2019

Cited by 7 | Viewed by 2751

Abstract

Post-pressure grouting is an effective method to improve bearing capacity of ordinary bored cast-in-situ piles. The migration of the grout along the pile side is regarded as an important mechanism responsible for the improvement of the pile capacity. Research into the penetration height [...] Read more.

Post-pressure grouting is an effective method to improve bearing capacity of ordinary bored cast-in-situ piles. The migration of the grout along the pile side is regarded as an important mechanism responsible for the improvement of the pile capacity. Research into the penetration height of the grout is of great important in evaluating the behavior of base grouted piles. In this paper, a prediction method of grouting penetration height along the shaft of the base grouted pile was proposed. Considering the balance and losses of the grout pressure during grouting, an iterative procedure was given to determine the penetration height of the grout in layered soils. Field test results were also provided to indicate the validity of the proposed method. Full article

(This article belongs to the Special Issue Computer-Aided Marine Structures’ Design)

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