Journal of Marine Science and Engineering

Research

17 pages, 7502 KiB

Open AccessArticle

A Numerical Study on the Effects of Ship-Generated Waves on a Moored Ship in Restricted Waterways Considering Initial Acceleration Process

by Ziqiang Zheng, Lu Zou and Zaojian Zou

J. Mar. Sci. Eng. 2023, 11(3), 483; https://doi.org/10.3390/jmse11030483 - 23 Feb 2023

Cited by 1 | Viewed by 1203

Abstract

In order to develop a reliable numerical method to investigate the effects of ship-generated waves on a moored ship in restricted waterways, this paper takes the MASHCON2022 benchmark model test case as the study object and simulates the whole process of a ship [...] Read more.

In order to develop a reliable numerical method to investigate the effects of ship-generated waves on a moored ship in restricted waterways, this paper takes the MASHCON2022 benchmark model test case as the study object and simulates the whole process of a ship passing a moored ship by using the unsteady Reynolds-Averaged Navier-Stokes (URANS) method coupled with the dynamic overset mesh technique. The initial acceleration process of the passing ship before approaching the moored ship is considered in the numerical simulations to reproduce the benchmark model tests more realistically. The numerical simulations with four acceleration modes are conducted. The comparisons among the numerical results and the test data verify that the prediction accuracy considering the acceleration process is obviously higher than that without the acceleration process, especially for the solitary wave system, and the results based on the linear acceleration agree with the test data best. The flow field results indicate that the impacts of the solitary wave system and the primary wave system on the moored ship are different: the solitary wave system induces significant positive pressures on the hull, while the primary wave system leads to remarkable negative pressures; both result in pronounced attitude variations of the moored ship, but the hydrodynamic forces and moments affected by the primary wave system are more pronounced. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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18 pages, 12214 KiB

Open AccessArticle

Numerical Study on Attitude and Resistance of a Side-Damaged Ship during Steady Flooding

by Wen Xue, Zhiliang Gao and Sangming Xu

J. Mar. Sci. Eng. 2022, 10(10), 1440; https://doi.org/10.3390/jmse10101440 - 06 Oct 2022

Cited by 2 | Viewed by 1254

Abstract

The computational fluid dynamics method is used to analyze the attitude and resistance of a side-damaged frigate DTMB-5415 during steady flooding phase. The volume of fluid method is used to capture the interface between water and air. The shear stress transport k- [...] Read more.

The computational fluid dynamics method is used to analyze the attitude and resistance of a side-damaged frigate DTMB-5415 during steady flooding phase. The volume of fluid method is used to capture the interface between water and air. The shear stress transport k-ω model is employed to include the turbulence effect. The dynamic overlapping grid method is utilized to deal with the mesh update due to the ship motion in the simulation. First, the resistance, floating position and wave profile of an intact ship for different forward speeds are calculated. By comparing the results with experimental data, the calculation method is verified. Then, the resistances, attitudes and flow fields for the ship in intact, side-damaged (symmetrical and asymmetric flooding) and damage-repaired conditions are calculated and compared. For the side-damaged condition, the main change of the ship’s attitude is that the ship’s sinkage increases as the forward speed increases. Compared with symmetrical flooding, the ship’s heel increases during asymmetric flooding, while the sinkage decreases. For symmetrical flooding, the resistance of the ship increases significantly compared to the intact ship case. The increased resistance is mainly caused by the increase of ship sinkage. The existence of opening that affects the flow field causes additional increase of ship resistance. The pressure resistance is the main component of increased resistance, which is similar to the asymmetric flooding case. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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18 pages, 10083 KiB

Open AccessArticle

URANS Calculation of Ship Heave and Pitch Motions in Marine Simulator Based on Overset Mesh

by Ziping Wang, Tingqiu Li, Junsheng Ren, Qiu Jin and Wenjun Zhou

J. Mar. Sci. Eng. 2022, 10(10), 1374; https://doi.org/10.3390/jmse10101374 - 26 Sep 2022

Cited by 1 | Viewed by 1766

Abstract

So as to improve the reliability and accuracy of marine simulators, it is essential to predict ship heave and pitch motions in regular waves. The motions of two ships, the international standard model KVLCC2 and the first training ship, “Yukun”, of Dalian Maritime [...] Read more.

So as to improve the reliability and accuracy of marine simulators, it is essential to predict ship heave and pitch motions in regular waves. The motions of two ships, the international standard model KVLCC2 and the first training ship, “Yukun”, of Dalian Maritime University, are simulated using a three-dimensional (3D) numerical wave tank based on the Unsteady Reynolds Averaged Navier–Stokes (URANS) equations. The free surface is captured by the volume of fluid (VOF) method, and an SST k-ω turbulence model is used to describe the turbulence flow. The numerical model is first validated for the standard KVLCC2 at three different speeds through a comparison with the published experimental data and the potential flow results. Then, numerical simulation is performed for the motion of the ship Yukun with different speeds under various sea conditions. The heave amplitude of the hull changes with the increase in the wavelength when the maximum value is reached. Upon comparing the RAOs of ship motions under different wave steepness conditions, it is apparent that the heave and pitch motions of ships nonlinearly decrease with an increase in wave steepness. The results were added to the database of the marine simulator to further improve the accuracy and realism of the simulator. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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31 pages, 13432 KiB

Open AccessArticle

Assessment of CFD-Based Ship Maneuvering Predictions Using Different Propeller Modeling Methods

by Changzhe Chen, Lu Zou, Zaojian Zou and Haipeng Guo

J. Mar. Sci. Eng. 2022, 10(8), 1131; https://doi.org/10.3390/jmse10081131 - 17 Aug 2022

Cited by 3 | Viewed by 1881

Abstract

Propeller modeling in virtual captive model tests is crucial to the prediction accuracy of ship maneuvering motion. In the present study, the Computational Fluid Dynamics (CFD) method with two propeller modeling methods, Sliding Mesh (SM) and Multiple Reference Frames (MRF), was used to [...] Read more.

Propeller modeling in virtual captive model tests is crucial to the prediction accuracy of ship maneuvering motion. In the present study, the Computational Fluid Dynamics (CFD) method with two propeller modeling methods, Sliding Mesh (SM) and Multiple Reference Frames (MRF), was used to simulate the captive model tests for a KVLCC2 tanker model. The virtual captive model tests, including for resistance, self-propulsion, rudder force, oblique towing, circular motion, oblique towing and steady turning tests with rudder angle, were conducted by solving the Reynolds-averaged Navier–Stokes (RANS) equations. The computed hydrodynamic forces, hydrodynamic derivatives, and hull-propeller-rudder interaction coefficients were validated against the available captive model test data and the CFD results obtained by a Body Force (BF) method in the literature. Then the standard turning circle and zig-zag maneuvers were simulated by using the MMG (Maneuvering Modeling Group) model with the computed hydrodynamic derivatives and hull-propeller-rudder interaction coefficients, and the results were validated against available free-running model test data. The most satisfactory agreement in terms of the ship hydrodynamic forces and maneuvering parameters and the most accurate rudder normal force were obtained by the SM method rather than by the MRF or the BF methods, while the lateral forces and yaw moments obtained by the SM and the MRF methods were all in good agreement with the model test data. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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18 pages, 52002 KiB

Open AccessArticle

Fast Multigrid Algorithm for Non-Linear Simulation of Intact and Damaged Ship Motions in Waves

by Ziping Wang, Tingqiu Li, Qiu Jin, Hao Guo, Ji Zhao and Junlin Qi

J. Mar. Sci. Eng. 2022, 10(8), 1101; https://doi.org/10.3390/jmse10081101 - 11 Aug 2022

Cited by 2 | Viewed by 1490

Abstract

This paper proposes a fast multigrid algorithm to simulate the non-linear motion of ships in both intact and damaged conditions. The simulations of ship motions in waves are known to require much time to calculate due to the strong non-linear interactions between ship [...] Read more.

This paper proposes a fast multigrid algorithm to simulate the non-linear motion of ships in both intact and damaged conditions. The simulations of ship motions in waves are known to require much time to calculate due to the strong non-linear interactions between ship and waves. To improve the calculation efficiency while retaining the accuracy, a prediction-correction strategy was designed to accelerate the simulation through three sets of locally refined meshes. The flow field was first estimated in a coarse mesh and then mapped to a locally refine mesh for further higher-fidelity corrections. A partitioned radial basis function (PRBF) method is proposed to interpolate and reconstruct the flow field for the refined mesh. A new two-phase flow solver was developed with a fast multigrid algorithm based on the Reynolds-averaged Navier–Stokes equations (RANSE). The new solver was applied to study the non-linear behavior of a damaged ship in beam waves and the effect of damaged compartments on ship rolling motion. Validation against the solution with the original method of single set meshes and experimental data indicates that the proposed algorithm yields satisfactory results while saving 30–40% of the computational time. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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21 pages, 11380 KiB

Open AccessArticle

Resistance Characteristics and Improvement of a Pump-Jet Propelled Wheeled Amphibious Vehicle

by Hai Luo, Jiangming Ding, Jiabing Jiang, Lingxun Li, Jie Gong and Ning Lyu

J. Mar. Sci. Eng. 2022, 10(8), 1092; https://doi.org/10.3390/jmse10081092 - 10 Aug 2022

Cited by 3 | Viewed by 1852

Abstract

Pump-jets have a relatively high propulsion efficiency at medium speed and in heavy-load conditions for wheeled amphibious vehicles. However, the geometry of amphibious vehicles is very special due to the installation requirements of the pump-jet, which results in an obvious resistance on the [...] Read more.

Pump-jets have a relatively high propulsion efficiency at medium speed and in heavy-load conditions for wheeled amphibious vehicles. However, the geometry of amphibious vehicles is very special due to the installation requirements of the pump-jet, which results in an obvious resistance on the wheels. In order to reduce the resistance of the amphibious vehicle, the resistance characteristics of the wheels are studied. Regarding a pump-jet-propelled wheeled amphibious vehicle, its wheel resistance characteristics in a wide speed range are firstly analyzed based on experiments and numerical simulations. By comparing the resistance of the amphibious vehicle with and without wheels, it is found that the hydrodynamic effect of wheels can increase the total resistance of the amphibious vehicle by 14~28%. Then, the wheel hydrodynamic effect is divided into local effect and global effect. By analyzing the changes in resistance, pressure distribution and streamline, the influence and hydro-mechanism of each effect are explored in detail. It is found that the longitudinal convex and concave structures formed by the wheels and wheel wells have a large negative effect on the total resistance. According to the hydro-mechanism, two resistance improvement approaches are proposed, which includes increasing wheel retraction and installing flat plates on the wheel well bottom. Finally, the ultimate resistance improvement model can reduce resistance by no less than 10% and power by on less than 8% in design speed. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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22 pages, 17723 KiB

Open AccessArticle

Experimental and Numerical Resistance Analysis for a Cruise Ship W/O Fin Stabilizers

by Rulin Yao, Long Yu, Qidong Fan and Xuefeng Wang

J. Mar. Sci. Eng. 2022, 10(8), 1054; https://doi.org/10.3390/jmse10081054 - 31 Jul 2022

Cited by 3 | Viewed by 2363

Abstract

Applying fin stabilizers is an effective solution for ship rolls on waves in a seaway. They generally consist of one or two pairs of retractable fins that are symmetrically mounted to both sides of the ship, effectively reducing the roll motion at low [...] Read more.

Applying fin stabilizers is an effective solution for ship rolls on waves in a seaway. They generally consist of one or two pairs of retractable fins that are symmetrically mounted to both sides of the ship, effectively reducing the roll motion at low or moderate speeds. Fin stabilizers are commonly used by cruise ships for the comfort and safety of passengers. However, there is still little experimental and numerical analysis of the fins’ effect on hydrodynamic performance. In this study, the resistance performance of a cruise ship was investigated with/without fin stabilizers at different fin angles and ship velocities by model tests and numerical analysis. The CFD analysis provides a flow-detailed interpretation of the physical phenomenon, especially at an asymmetric maximum fin angle. The significant fin-induced resistance is newly discovered and averages up to 19% in calm water conditions, while the added resistance in waves is evaluated with a smaller increment up to 1.31%. By comparing the numerical and experimental results, this study provides insight into the resistance induced by overhanging fins, which provides an accurate prediction reference for cruise ship performance and benefits the fin stabilizers’ design and selection. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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19 pages, 12033 KiB

Open AccessArticle

CFD-FEM Analysis of Flow-Induced Vibrations in Waterjet Propulsion Unit

by Yuanxing Dai, Zhenghao Liu, Wei Zhang, Jianping Chen and Jianguo Liu

J. Mar. Sci. Eng. 2022, 10(8), 1032; https://doi.org/10.3390/jmse10081032 - 27 Jul 2022

Cited by 2 | Viewed by 1576

Abstract

This paper investigates the problem of vibration in an axial flow waterjet propeller with high power density and low specific speed. Based on fluid–structure coupling vibration analysis, combined with modal analysis and ship tests, the unsteady fluid–structure coupling of a waterjet propeller is [...] Read more.

This paper investigates the problem of vibration in an axial flow waterjet propeller with high power density and low specific speed. Based on fluid–structure coupling vibration analysis, combined with modal analysis and ship tests, the unsteady fluid–structure coupling of a waterjet propeller is examined, and the vibration characteristics of the propeller under different speed conditions are studied. The results show that the vibrations of the waterjet propeller mainly come from the frequency response of the rotor and the structural resonance response. The frequency distribution characteristics and amplitude intensity are observed to increase with increasing rotation speed. The variations in the propeller vibration characteristics, with respect to parameter changes, are analyzed at different gap spacings between the rotor and stator, allowing the variation law of vibration intensity with rotor stator spacing to be obtained. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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24 pages, 3479 KiB

Open AccessArticle

Comparison between the RANS Simulations of Double-Body Flow and Water–Air Flow around a Ship in Static Drift and Circle Motions

by Long Jiang, Jianxi Yao and Zuyuan Liu

J. Mar. Sci. Eng. 2022, 10(7), 970; https://doi.org/10.3390/jmse10070970 - 14 Jul 2022

Cited by 2 | Viewed by 1702

Abstract

Manoeuvrability is one of the important ship hydrodynamic performances. That is closely related to the safety and economy of navigation. The development of a high-accuracy and high-efficiency numerical method to compute the forces and moments on manoeuvring ships has been the main task [...] Read more.

Manoeuvrability is one of the important ship hydrodynamic performances. That is closely related to the safety and economy of navigation. The development of a high-accuracy and high-efficiency numerical method to compute the forces and moments on manoeuvring ships has been the main task for ship manoeuvring predictions. The numerical method by solving RANS (Reynolds-Averaged Navier–Stokes) equations may be the most used one nowadays for the computations of ship manoeuvring forces and moments. However, applying a RANS tool for ship manoeuvring prediction remains very low efficiency, especially considering the six-degrees-of-freedom ship motions on the water surface. Thus, it is very necessary to introduce a few assumptions to reduce the computational time when applying a RANS tool, e.g., the assumptions of double-body flow and body force propeller, and consequently improve the application efficiency. Generally speaking, the assumption of double-body flow, in which the free-surface effects are neglected, is more suitable for low-speed ships. Nevertheless, rare publications have been reported relating to how this assumption affects the accuracy of the computed manoeuvring forces and moments. To this end, this article presents a comparative study between the RANS simulations of double-body flow and water–air flow around a container ship performing static drift and static circle motions. Three ship speeds, corresponding to the Froude numbers 0.156, 0.201, and 0.260, respectively, are considered during the simulations. The computed side forces and yaw moments obtained by the water–air flow simulations are closer to the available experimental data than that obtained by the double-body flow simulations for all ship speeds. The computed surge forces obtained by water–air flow simulations also agree well with the experimental data, whereas the computed surge forces obtained by the double-body flow simulations are wrong. The reasons are analyzed by comparing the pressure distributions on the ship surface and the flow separations around the ship. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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14 pages, 4496 KiB

Open AccessArticle

Comparative Study on Added Resistance and Seakeeping Performance of X-Bow and Wave-Piercing Monohull in Regular Head Waves

by Shuling Chen, Beilei Zou, Changzhi Han and Shiqiang Yan

J. Mar. Sci. Eng. 2022, 10(6), 813; https://doi.org/10.3390/jmse10060813 - 14 Jun 2022

Cited by 3 | Viewed by 2265

Abstract

Bow shape has been recognized as an important factor influencing the seakeeping performance and added resistance of ships. This paper presents a numerical comparative study on added resistance and seakeeping of model ships with ‘X-bow’ and a wave-piercing monohull in regular head waves [...] Read more.

Bow shape has been recognized as an important factor influencing the seakeeping performance and added resistance of ships. This paper presents a numerical comparative study on added resistance and seakeeping of model ships with ‘X-bow’ and a wave-piercing monohull in regular head waves using a computational fluid dynamics (CFD) software. Different wave heights, wavelengths and forward speeds are considered in the systematic investigation in order to characterize the added resistance and wave-induced motions, and to explore the local wave patterns. The results show a considerably different hydrodynamic characteristic by different bow shapes. Full article

(This article belongs to the Special Issue Hydrodynamic Analysis on Ship Performance)

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