Journal of Marine Science and Engineering

Research

27 pages, 4398 KB

Open AccessArticle

Motion Characteristics and Drag-Reduction Optimization of Moonpool Drillships in Irregular Waves

by Junming Hu, Zhen Zhang, Chengshuai Song, Jiaxia Wang, Xueying Yu and Daiyu Zhang

J. Mar. Sci. Eng. 2026, 14(10), 890; https://doi.org/10.3390/jmse14100890 (registering DOI) - 11 May 2026

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This study analyzes the effects of different moonpool configurations on drillship hydrodynamics using the Reynolds-averaged Navier–Stokes (RANS) equations. A three-dimensional numerical wave tank is established to realize the prediction and validation of the hydrodynamic performance of irregular waves and the interaction between irregular [...] Read more.

This study analyzes the effects of different moonpool configurations on drillship hydrodynamics using the Reynolds-averaged Navier–Stokes (RANS) equations. A three-dimensional numerical wave tank is established to realize the prediction and validation of the hydrodynamic performance of irregular waves and the interaction between irregular waves and structures. Combined with the selection of the drillships with relatively favorable resistance performance among different moonpool configurations under calm-water navigation conditions, further studies are carried out on the motion characteristics and drag-reduction optimization of the rectangular- and square-moonpool drillships under irregular wave conditions. Comparative analysis of the numerical results shows that different moonpool shapes result in different drag-increase effects under calm-water conditions, and the moonpool-induced drag increase mainly originates from added residuary resistance. Relative to the non-moonpool baseline drillship, the installation of a moonpool under irregular wave conditions notably elevates the resistance amplitude and amplifies the heave and pitch responses, with a more prominent impact observed on pitch, while also modifying the natural frequency characteristics of the moonpool-equipped drillship. Introducing appropriate rounded corners at the bottom of the moonpool can effectively reduce the resistance of the moonpool drillship and significantly decrease the amplitudes of heave and pitch responses under irregular wave conditions. Based on the present study, a bottom rounded-corner radius of 40 mm effectively improves the hydrodynamic performance of the moonpool drillship in irregular waves. The numerical results provide direct theoretical and design guidance for drag reduction and motion-performance enhancement of moonpool-equipped drillships, highlighting their engineering applicability. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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27 pages, 42165 KB

Open AccessArticle

A Method for Efficient Reproduction of Target Wave Trains Containing Freak Waves

by Aimin Wang, Dietao Ding, Tao Zhou, Xu Bai and Daolei Wu

J. Mar. Sci. Eng. 2026, 14(9), 839; https://doi.org/10.3390/jmse14090839 - 30 Apr 2026

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Abstract

Freak waves can cause damage or capsize marine structures. The efficient fixed-point generation of target wave trains containing freak waves in laboratories or numerical wave tanks is a crucial method for marine structure design and disaster inversion assessment. This study proposes a local [...] Read more.

Freak waves can cause damage or capsize marine structures. The efficient fixed-point generation of target wave trains containing freak waves in laboratories or numerical wave tanks is a crucial method for marine structure design and disaster inversion assessment. This study proposes a local coefficient assignment method. After no more than three iterations of local wave train processing, the method achieves accurate generation of measured freak wave trains at different positions. Among the results, the maximum crest error for the “New Year Wave” is less than 3%, and the simulation achieves excellent agreement in significant wave height, period, and overall wave surface elevation with the target wave surface. The assignment coefficient curve of the typical freak wave event “New Year Wave” within the farthest fixed-point generation range of the numerical simulation in this paper is provided, enabling high-precision one-time generation of the “New Year Wave” at any desired position. The resulting maximum wave height error is less than 5%, satisfying the application requirements of deep-water waves under different water depth conditions. Furthermore, based on the simulation results, wavelet transform analysis is performed on the wave train data to investigate the evolution characteristics of wave energy before, during, and after the occurrence of the freak wave. The findings of this study have strong practical engineering significance for research on the propagation and evolution characteristics of highly nonlinear waves, as well as for the design and analysis of wave loads on marine structures. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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22 pages, 14278 KB

Open AccessArticle

Hydrodynamic and Trim Analysis of a Dihedral Bulbous Bow on a Longliner Hull

by Héctor Rubén Díaz Ojeda, Yifu Zhang, Stephen Turnock and Francisco Pérez Arribas

J. Mar. Sci. Eng. 2026, 14(4), 382; https://doi.org/10.3390/jmse14040382 - 17 Feb 2026

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Abstract

This study evaluates the hydrodynamic performance of a displacement-type FAO longliner fishing vessel fitted with a surface-piercing dihedral bulbous bow. Unlike conventional submerged bulbs, this configuration partially emerges at the free surface. Hydrodynamic behaviour was analysed under heavy- and light-load conditions using both [...] Read more.

This study evaluates the hydrodynamic performance of a displacement-type FAO longliner fishing vessel fitted with a surface-piercing dihedral bulbous bow. Unlike conventional submerged bulbs, this configuration partially emerges at the free surface. Hydrodynamic behaviour was analysed under heavy- and light-load conditions using both computational and experimental fluid dynamics. Results show that the dihedral bulb significantly reduces total resistance beyond a critical speed of approximately 6 knots, whilst also affecting dynamic trim and vertical hydrodynamic forces. Full-scale effective power was estimated by extrapolating model results according to ITTC procedures. This study confirms that dihedral bulbous bows are well suited for retrofit applications on small fishing vessels under 20 m in length, achieving maximum resistance reductions of about 18% at higher speeds. These gains translate into notable fuel savings and reduced greenhouse gas emissions, making the retrofit both economically and environmentally advantageous. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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30 pages, 8901 KB

Open AccessArticle

Research on Hydrodynamic Characteristics and Drag Reduction Optimization of Drillships with Moonpools

by Junming Hu, Chengshuai Song, Jiaxian Deng, Jiaxia Wang, Xiaojie Zhao and Daiyu Zhang

J. Mar. Sci. Eng. 2026, 14(2), 215; https://doi.org/10.3390/jmse14020215 - 20 Jan 2026

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Abstract

This paper analyzes the influence of moonpools on the hydrodynamic performance of drillships using the Reynolds-averaged Navier–Stokes (RANS) method. A three-dimensional numerical wave tank is established to realize regular waves and to perform prediction and validation of the KCS ship’s performance in calm [...] Read more.

This paper analyzes the influence of moonpools on the hydrodynamic performance of drillships using the Reynolds-averaged Navier–Stokes (RANS) method. A three-dimensional numerical wave tank is established to realize regular waves and to perform prediction and validation of the KCS ship’s performance in calm water and head seas. After selecting optimal moonpool configurations under calm conditions, seakeeping analyses for a rectangular-moonpool drillship in waves and drag-reduction optimization in calm water and head seas are conducted. The comparative analysis shows that in calm-water navigation, different moonpool shapes lead to different added-resistance effects, and the drillship with a rectangular moonpool shows overall better performance in resistance and running attitude; the added resistance due to the moonpool mainly originates from the additional residual resistance. The sustained energy supply to the clockwise vortex within the moonpool is maintained by the continuous mass exchange between the water flow beneath the ship’s bottom and the water inside the moonpool. Under regular waves, the presence of a moonpool leads to an increase in the total resistance experienced by the drillship. A flange device can effectively reduce the mean amplitude of waves inside the moonpool, and when the flange is installed 10 mm above the still water level with a length of 120 mm, its drag-reduction effect is better. The flange structure can effectively improve the hydrodynamic characteristics of the drillship in waves. The numerical conclusions provide a reference value for the engineering application of drillships with moonpool structures. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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20 pages, 2708 KB

Open AccessArticle

Experimental Determination of Forces and Hydrodynamic Coefficients on Vertical Cylinders Under Wave and Current Conditions

by Oier Peña Vega, Urko Izquierdo, Iñigo Albaina, Gustavo A. Esteban, Iñigo Bidaguren and Jesús María Blanco

J. Mar. Sci. Eng. 2026, 14(2), 129; https://doi.org/10.3390/jmse14020129 - 8 Jan 2026

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Abstract

This paper presents an extensive experimental study on the hydrodynamic behavior of vertical cylinders representative of the structural elements of offshore floating photovoltaic (OFPV) platforms under both wave and steady-current conditions. The objectives are to determine reliable hydrodynamic coefficients for Morison-type formulations and [...] Read more.

This paper presents an extensive experimental study on the hydrodynamic behavior of vertical cylinders representative of the structural elements of offshore floating photovoltaic (OFPV) platforms under both wave and steady-current conditions. The objectives are to determine reliable hydrodynamic coefficients for Morison-type formulations and to analyze the wake effects between cylinders for modular floating configurations. Tests under regular waves are conducted in a 25 m long wave flume at the Energy Engineering Department of the Bilbao School of Engineering. The obtained inertia and drag coefficients follow the expected trends for a wide range of Keulegan–Carpenter (KC) numbers, aligning well with classical experimental studies. Steady-current experiments are conducted in the same flume using a towing tank method. Again, the obtained drag coefficients align well with previous studies. As for the wake provoked by the first cylinder on the second cylinder located downstream at one of four different distances, in the wave cases, the wake attenuation is minimal and rapid recovery of the flow is observed for a wide range of KC values, while in the steady-current cases, the wake is stronger and affects the forces acting on the second cylinder. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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22 pages, 6974 KB

Open AccessArticle

Numerical Analysis of Air-Injection Drag Reduction for the KVLCC2 Hull Using the VOF Interface-Capturing Method

by Xiaojie Zhao, Yanping Hao and Qi Zhang

J. Mar. Sci. Eng. 2025, 13(12), 2253; https://doi.org/10.3390/jmse13122253 - 27 Nov 2025

Viewed by 906

Abstract

To investigate the air layer drag reduction and the related flow field characteristics of ships, the gas–liquid two-phase numerical model using the VOF solver in STAR-CCM+ has been established, considering the effects of free surface and surface tension. The numerical model is first [...] Read more.

To investigate the air layer drag reduction and the related flow field characteristics of ships, the gas–liquid two-phase numerical model using the VOF solver in STAR-CCM+ has been established, considering the effects of free surface and surface tension. The numerical model is first validated through experimental results for the drag reduction by air-injection on a simplified ship model. Then, the numerical simulations for the KVLCC2 at varying speeds and air-injection rates are conducted, considering different ship attitudes and air-injection surface configurations. The impacts of flow velocity, air-injection rates, ship attitude and air-injection configurations on air layer drag reduction are analyzed. The distributions of air and pressure around the ship and their influence mechanisms on drag reduction are discussed. The simulation results show that the drag reduction exhibits a positive correlation with air-injection rate until it reaches an optimal peak value. The combined action of the incoming flow and injection velocities causes the vortex recirculation of the air layer under the ship, leading to its disruption and the subsequent formation of air-free zones on the hull bottom. High air-injection rates and the stern trim induce air layer lateral spillage, increasing frictional resistance on the hull side surfaces. An air layer on the stern surface will reduce the viscous pressure resistance by changing the flow separation near the ship stern. Air-layer coverage area is closely correlated with inflow velocity and injection surface configurations. The reasonable configurations of the air-injection surfaces can significantly improve the drag reduction. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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18 pages, 3158 KB

Open AccessArticle

From Kelvin Wave Patterns to Ship Displacement: An Inverse Prediction Framework Based on a Hull Form Database

by Chao Ma, Linwei Wang, Yingjiang Zhao, Haolin Yang, Haoqing Huang and Bohan Cao

J. Mar. Sci. Eng. 2025, 13(10), 2019; https://doi.org/10.3390/jmse13102019 - 21 Oct 2025

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Abstract

The estimation of a ship’s displacement volume, ∇, from remote sensing data is of considerable practical value for maritime surveillance and vessel characterization. This paper introduces a practical framework for the inverse estimation of displacement volume from Kelvin ship waves, building upon a [...] Read more.

The estimation of a ship’s displacement volume, ∇, from remote sensing data is of considerable practical value for maritime surveillance and vessel characterization. This paper introduces a practical framework for the inverse estimation of displacement volume from Kelvin ship waves, building upon a prior study through two key extensions. First, the wave amplitude function is recovered using Fourier series expansions combined with the stationary phase method. The displacement volume is then estimated via a two-step procedure: an initial estimate is obtained by identifying a hull with similar amplitude characteristics from a database, followed by a refinement that incorporates discrepancies between the target and candidate wave amplitude functions. In the case studied, the proposed approach achieves a prediction error of

4.02 %

, demonstrating its potential for non-invasive extraction of hull information from remote sensing data. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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27 pages, 5203 KB

Open AccessArticle

Mechanisms of Freak Wave Generation from Random Wave Evolution in 3D Island-Reef Topography

by Aimin Wang, Tao Zhou, Dietao Ding, Xinyu Ma and Li Zou

J. Mar. Sci. Eng. 2025, 13(10), 1926; https://doi.org/10.3390/jmse13101926 - 9 Oct 2025

Viewed by 860

Abstract

The mechanisms of freak wave generation in 3D island-reef topography are investigated. Four types of freak waves are investigated, based on the wavelet transform for examining the characteristics of freak waves and their mechanism. The freak waves come from a three-dimensional experimental terrain [...] Read more.

The mechanisms of freak wave generation in 3D island-reef topography are investigated. Four types of freak waves are investigated, based on the wavelet transform for examining the characteristics of freak waves and their mechanism. The freak waves come from a three-dimensional experimental terrain model in a random wave. The wavelet energy spectrum, scale-averaged and time-averaged wavelet spectrum are considered. A new parameter (scale-centroid wavelet spectrum) is defined, based on the wavelet transform algorithm, to quantitatively analyze and further estimate the energy transfer process. The results suggest that the occurrence of freak waves is associated with the gradual alignment of the phases of wave components. The nonlinear interaction in terms of wavelet cross-bispectrum implies that wave–wave interaction, especially with high-frequency components, is obviously enhanced during a freak wave occurrence. The energy transforms to a high frequency during a freak wave occurrence. The current result forms a definite indication that the occurrence of freak waves is caused by the combined effects of linear superposition and nonlinear interactions. Linear superposition begins to take effect long before the freak wave occurs, whereas nonlinear interactions primarily occur during the shorter period just before the freak wave forms. It provides an important reference for the prediction of abnormal waves. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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17 pages, 8174 KB

Open AccessArticle

Calculation and Analysis of Rolling Hydrodynamic Coefficients of Free-Flooding Ship Based on CFD

by Chaofan Li, Yuehu Teng, Min Xu and Renchuan Zhu

J. Mar. Sci. Eng. 2025, 13(10), 1857; https://doi.org/10.3390/jmse13101857 - 25 Sep 2025

Cited by 1 | Viewed by 1189

Abstract

As free-flooding ships are a type of vessel with openings on their hull surfaces, accurately calculating and analyzing their roll hydrodynamic coefficients is of great significance for ship motion prediction. Based on the STAR CCM+ platform that employs the computational fluid dynamics (CFD) [...] Read more.

As free-flooding ships are a type of vessel with openings on their hull surfaces, accurately calculating and analyzing their roll hydrodynamic coefficients is of great significance for ship motion prediction. Based on the STAR CCM+ platform that employs the computational fluid dynamics (CFD) method, this paper first conducts numerical simulations of the forced roll motion of a damaged DTMB-5415 ship model. The applicability of this method to side-opening ship types is verified by comparing with experimental results. Subsequently, this numerical method is applied to simulate the forced roll of a free-flooding aquaculture ship under different working conditions, and the roll hydrodynamic coefficients of its hull and internal compartments are calculated and analyzed. The roll hydrodynamic coefficients of the intact ship and the free-flooding ship are compared. The results indicate the characteristics of roll hydrodynamic coefficients of free-flooding ships, and this research will facilitate the prediction of roll motion for this ship type. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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22 pages, 5038 KB

Open AccessArticle

Numerical Investigation of Flow Field Characteristics Around a Monopile Foundation with Collar Protection

by Lei Wu, Hao Meng, Haifei Sun, Lingfei Yu, Dake Chen, Xiyu Zhao and Dawei Guan

J. Mar. Sci. Eng. 2025, 13(10), 1841; https://doi.org/10.3390/jmse13101841 - 23 Sep 2025

Cited by 1 | Viewed by 820

Abstract

Collar structures are widely used to protect monopile foundations from scour, but their geometric obstruction hinders direct observation of the surrounding flow in physical experiments. To overcome this limitation, this study employs large-eddy simulation (LES) to investigate the flow characteristics around a monopile [...] Read more.

Collar structures are widely used to protect monopile foundations from scour, but their geometric obstruction hinders direct observation of the surrounding flow in physical experiments. To overcome this limitation, this study employs large-eddy simulation (LES) to investigate the flow characteristics around a monopile with collar protection. The LES model was validated against well-documented experimental data of pile-induced flow, confirming its reliability. Simulations under flat-bed and equilibrium scour conditions were conducted to evaluate the effects of the collar on time-averaged velocity, vortex dynamics, and turbulence intensity. The results show that the collar substantially weakens the upstream accelerated flow, suppresses horseshoe vortex formation, and reduces both the strength and extent of sidewall currents. Under flatbed conditions, the side-flow intensity decreases by 24.3% and the accelerated flow area is reduced by 93.3%. A counter-rotating vortex beneath the collar dissipates kinetic energy and simplifies the near-bed vortex system, thereby mitigating scour. However, the protective effect diminishes with increasing inflow velocity, with turbulence intensity rising by 159% for a 14% velocity increase. Overall, this study provides deeper insights into the protective mechanisms of collar structures, advancing the understanding of their effectiveness and limitations in monopile scour protection. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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18 pages, 8099 KB

Open AccessArticle

Machine Learning-Based Recursive Prediction and Application of Green’s Function of Water-Wave Radiation and Diffraction

by Minmin Zheng, Xinsheng Fan, Chuanqing Li, Jianpeng Li, Duolun He and Renchuan Zhu

J. Mar. Sci. Eng. 2025, 13(8), 1488; https://doi.org/10.3390/jmse13081488 - 1 Aug 2025

Cited by 1 | Viewed by 776

Abstract

The frequency-domain free-surface Green’s function method is widely used in solving ship hydrodynamic problems, with its core challenge lying in the computation of the Green’s function and its partial derivatives. This study analyzes the relationship between the free-surface Green’s function and its derivatives, [...] Read more.

The frequency-domain free-surface Green’s function method is widely used in solving ship hydrodynamic problems, with its core challenge lying in the computation of the Green’s function and its partial derivatives. This study analyzes the relationship between the free-surface Green’s function and its derivatives, proposing a machine learning-based recursive prediction method termed the pulsating source recursive prediction method. The accuracy and efficiency of this method under various parameter settings are investigated, and its application to the hydrodynamic calculations of container ship S175 and a bulk carrier is demonstrated. Results show that the predicted Green’s function achieves an accuracy of 3–6 decimals, with computational efficiency surpassing numerical methods and matching analytical approaches. The hydrodynamic results are reliable, confirming the method’s practical value. Full article

(This article belongs to the Special Issue Advancements in Marine Hydrodynamics and Structural Optimization)

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