Journal of Marine Science and Engineering

Editorial

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3 pages, 160 KiB

Open AccessEditorial

Fluid/Structure Interactions

by Yuriy A. Semenov

J. Mar. Sci. Eng. 2022, 10(2), 159; https://doi.org/10.3390/jmse10020159 - 26 Jan 2022

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Abstract

This Special Issue contains 12 papers devoted to fluid/structure interaction (FSI) problems [...] Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

Research

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12 pages, 482 KiB

Open AccessArticle

Cavity Detachment from a Wedge with Rounded Edges and the Surface Tension Effect

by Yuriy N. Savchenko, Georgiy Y. Savchenko and Yuriy A. Semenov

J. Mar. Sci. Eng. 2021, 9(11), 1253; https://doi.org/10.3390/jmse9111253 - 11 Nov 2021

Cited by 1 | Viewed by 1743

Abstract

Cavity flow around a wedge with rounded edges was studied, taking into account the surface tension effect and the Brillouin–Villat criterion of cavity detachment. The liquid compressibility and viscosity were ignored. An analytical solution was obtained in parametric form by applying the integral [...] Read more.

Cavity flow around a wedge with rounded edges was studied, taking into account the surface tension effect and the Brillouin–Villat criterion of cavity detachment. The liquid compressibility and viscosity were ignored. An analytical solution was obtained in parametric form by applying the integral hodograph method. This method gives the possibility of deriving analytical expressions for complex velocity and for potential, both defined in a parameter plane. An expression for the curvature of the cavity boundary was obtained analytically. By using the dynamic boundary condition on the cavity boundary, an integral equation in the velocity modulus was derived. The particular case of zero surface tension is a special case of the solution. The surface tension effect was computed over a wide range of the Weber number for various degrees of cavitation development. Numerical results are presented for the flow configuration, the drag force coefficient, and the position of cavity detachment. It was found that for each radius of the edges, there exists a critical Weber number, below which the iterative solution process fails to converge, so a steady flow solution cannot be computed. This critical Weber number increases as the radius of the edge decreases. As the edge radius tends to zero, the critical Weber number tends to infinity, or a steady cavity flow cannot be computed at any finite Weber number in the case of sharp wedge edges. This shows some limitations of the model based on the Brillouin–Villat criterion of cavity detachment. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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18 pages, 6169 KiB

Open AccessArticle

Effect of Roughness of Mussels on Cylinder Forces from a Realistic Shape Modelling

by Antoine Marty, Franck Schoefs, Thomas Soulard, Christian Berhault, Jean-Valery Facq, Benoît Gaurier and Gregory Germain

J. Mar. Sci. Eng. 2021, 9(6), 598; https://doi.org/10.3390/jmse9060598 - 31 May 2021

Cited by 18 | Viewed by 3106

Abstract

After a few weeks, underwater components of offshore structures are colonized by marine species and after few years this marine growth can be significant. It has been shown that it affects the hydrodynamic loading of cylinder components such as legs and braces for [...] Read more.

After a few weeks, underwater components of offshore structures are colonized by marine species and after few years this marine growth can be significant. It has been shown that it affects the hydrodynamic loading of cylinder components such as legs and braces for jackets, risers and mooring lines for floating units. Over a decade, the development of Floating Offshore Wind Turbines highlighted specific effects due to the smaller size of their components. The effect of the roughness of hard marine growth on cylinders with smaller diameter increased and the shape should be representative of a real pattern. This paper first describes the two realistic shapes of a mature colonization by mussels and then presents the tests of these roughnesses in a hydrodynamic tank where three conditions are analyzed: current, wave and current with wave. Results are compared to the literature with a similar roughness and other shapes. The results highlight the fact that, for these realistic roughnesses, the behavior of the rough cylinders is mainly governed by the flow and not by their motions. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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10 pages, 10388 KiB

Open AccessArticle

Effect of Boundary Conditions on Fluid–Structure Coupled Modal Analysis of Runners

by Dianhai Liu, Xiang Xia, Jing Yang and Zhengwei Wang

J. Mar. Sci. Eng. 2021, 9(4), 434; https://doi.org/10.3390/jmse9040434 - 17 Apr 2021

Cited by 5 | Viewed by 2433

Abstract

To predict the resonance characteristics of hydraulic machinery, it is necessary to accurately calculate the natural modes of the runners in the operating environment. However, in the existing research, the boundary conditions of the numerical modal analysis of the runner were not unified. [...] Read more.

To predict the resonance characteristics of hydraulic machinery, it is necessary to accurately calculate the natural modes of the runners in the operating environment. However, in the existing research, the boundary conditions of the numerical modal analysis of the runner were not unified. In this paper, numerical modal analysis of a prototype Francis pump turbine runner was carried out using the acoustic–structure coupling method. The results of three different constraints were compared. The influence of the energy loss on the chamber wall on the natural modes of the runner was studied by the absorption boundary. The results show that the constraint condition (especially the rotating shaft) has significant impacts on the torsional mode, the radial mode, the 1 nodal-diameter mode, and the 0 nodal-circle mode, and the maximum differences in the natural frequencies under different conditions are 69.3%, 56.4%, 35.1%, and 9.4%, respectively. The change of the natural frequencies is closely related to the modal shapes. On the other hand, the energy loss on the wall mainly affects the nodal-circle modes, and the influence on other modes is negligible. The results can provide references for the design and resonance characteristics analysis of hydraulic machinery runners. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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20 pages, 5178 KiB

Open AccessArticle

The One-Way FSI Method Based on RANS-FEM for the Open Water Test of a Marine Propeller at the Different Loading Conditions

by Mobin Masoomi and Amir Mosavi

J. Mar. Sci. Eng. 2021, 9(4), 351; https://doi.org/10.3390/jmse9040351 - 24 Mar 2021

Cited by 16 | Viewed by 3669

Abstract

This paper aims to assess a new fluid–structure interaction (FSI) coupling approach for the vp1304 propeller to predict pressure and stress distributions with a low-cost and high-precision approach with the ability of repeatability for the number of different structural sets involved, other materials, [...] Read more.

This paper aims to assess a new fluid–structure interaction (FSI) coupling approach for the vp1304 propeller to predict pressure and stress distributions with a low-cost and high-precision approach with the ability of repeatability for the number of different structural sets involved, other materials, or layup methods. An outline of the present coupling approach is based on an open-access software (OpenFOAM) as a fluid solver, and Abaqus used to evaluate and predict the blade’s deformation and strength in dry condition mode, which means the added mass effects due to propeller blades vibration is neglected. Wherein the imposed pressures on the blade surfaces are extracted for all time-steps. Then, these pressures are transferred to the structural solver as a load condition. Although this coupling approach was verified formerly (wedge impact), for the case in-hand, a further verification case, open water test, was performed to evaluate the hydrodynamic part of the solution with an e = 7.5% average error. A key factor for the current coupling approach is the rotational rate interrelated between two solution domains, which should be carefully applied in each time-step. Finally, the propeller strength assessment was performed by considering the blades’ stress and strain for different load conditions. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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20 pages, 7224 KiB

Open AccessArticle

Study on Vibration Characteristics of Marine Centrifugal Pump Unit Excited by Different Excitation Sources

by Cui Dai, Yuhang Zhang, Qi Pan, Liang Dong and Houlin Liu

J. Mar. Sci. Eng. 2021, 9(3), 274; https://doi.org/10.3390/jmse9030274 - 3 Mar 2021

Cited by 22 | Viewed by 2921

Abstract

In order to study the vibration mechanism of a marine centrifugal pump unit and explore the contribution of vibration caused by different vibration excitation sources, a marine centrifugal pump with a specific speed of 66.7 was used for research. A numerical calculation model [...] Read more.

In order to study the vibration mechanism of a marine centrifugal pump unit and explore the contribution of vibration caused by different vibration excitation sources, a marine centrifugal pump with a specific speed of 66.7 was used for research. A numerical calculation model of the flow field and electromagnetic field of the pump unit was established to analyze the frequency spectrum characteristics and contribution of pump unit vibration caused by different excitation sources. Using the modal superposition method, the vibration characteristics of the pump unit caused by fluid excitation and electromagnetic excitation were analyzed. The results show that the main frequency of pump unit vibration caused by fluid excitation was at the 1× blade passing frequency. The main frequency of pump unit vibration caused by electromagnetic excitation was at the 2× utility frequency. The contribution of different excitation sources to the vibration of marine centrifugal pump unit was in the following order: fluid excitation on the inner surface of the pump

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electromagnetic excitation

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fluid excitation in the impeller. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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15 pages, 2705 KiB

Open AccessArticle

Effect of Cutting Ratio and Catch on Drag Characteristics and Fluttering Motions of Midwater Trawl Codend

by Wei Liu, Hao Tang, Xinxing You, Shuchuang Dong, Liuxiong Xu and Fuxiang Hu

J. Mar. Sci. Eng. 2021, 9(3), 256; https://doi.org/10.3390/jmse9030256 - 28 Feb 2021

Cited by 17 | Viewed by 3392

Abstract

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of [...] Read more.

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of a midwater trawl codend. These are generally affected by catch, cutting ratio, mesh size, and twine diameter. In this study, six nylon codend models with different cutting ratios (no cutting, 6:1, 5:1, 4:1, 7:2, and 3:1) were designed and tested in a professional flume tank under two conditions (empty codends and codends with catch) and five current speeds to obtain the drag force, spatial geometry, and movement trend. As the cutting ratio of empty codends decreased, the drag force decreased, and the drag coefficient increased. The unfolding degree of codend netting and the height of empty codends were found to be directly proportional to the current speed and inversely proportional to the cutting ratio. The positional amplitude of codend with cutting ratio 4:1 was the smallest for catch. The drag force of codends with catch increased as the current speed increased, and first decreased and then increased as the cutting ratio decreased. To ensure the best stability and minimum drag force of the codend, it is recommended to use the 4:1 cutting ratio codend. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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24 pages, 14802 KiB

Open AccessArticle

Investigation of the Starting-Up Axial Hydraulic Force and Structure Characteristics of Pump Turbine in Pump Mode

by Zhongyu Mao, Ran Tao, Funan Chen, Huili Bi, Jingwei Cao, Yongyao Luo, Honggang Fan and Zhengwei Wang

J. Mar. Sci. Eng. 2021, 9(2), 158; https://doi.org/10.3390/jmse9020158 - 5 Feb 2021

Cited by 27 | Viewed by 4297

Abstract

During the starting up of the pump mode in pump turbines, the axial hydraulic force acting on the runner would develop with the guide vane opening. It causes deformation and stress on the support bracket, main shaft and runner, which influence the operation [...] Read more.

During the starting up of the pump mode in pump turbines, the axial hydraulic force acting on the runner would develop with the guide vane opening. It causes deformation and stress on the support bracket, main shaft and runner, which influence the operation security. In this case, the axial hydraulic force of the pump turbine is studied during the starting up of pump mode. Its influences on the support bracket and main shaft are investigated in detail. Based on the prediction results of axial hydraulic force, the starting-up process can be divided into “unsteady region” and “Q flat region” with obviously different features. The mechanism is also discussed by analyzing pressure distributions and streamlines. The deformation of the support bracket and main shaft are found to have a relationship with the resultant force on the crown and band. A deflection is found on the deformation of the runner with the nodal diameter as the midline in the later stages of the starting-up process. The reason is discussed according to pressure distributions. The stress concentration of the support bracket is found on the connection between thrust seating and support plates. The stress of the runner is mainly on the connection between the crown and the blade’s leading-edge. This work will provide more useful information and strong references for similar cases. It will also help in the design of pump turbine units with more stabilized systems for reducing over-loaded hydraulic force, and in the solving of problems related to structural characteristics. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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16 pages, 6589 KiB

Open AccessArticle

Derivation of Engineering Design Criteria for Flow Field Around Intake Structure: A Numerical Simulation Study

by Lee Hooi Chie and Ahmad Khairi Abd Wahab

J. Mar. Sci. Eng. 2020, 8(10), 827; https://doi.org/10.3390/jmse8100827 - 21 Oct 2020

Cited by 9 | Viewed by 5735

Abstract

The primary environmental impact caused by seawater intake operation is marine life impingement resulting from the intake velocity. Environmental Protection Agency (EPA) of United State has regulated the use of velocity cap fitted at intake structures to reduce the marine life impingement. The [...] Read more.

The primary environmental impact caused by seawater intake operation is marine life impingement resulting from the intake velocity. Environmental Protection Agency (EPA) of United State has regulated the use of velocity cap fitted at intake structures to reduce the marine life impingement. The engineering design parameters of velocity cap has not been well explored to date. This study has been set to determine the fundamental relationships between intake velocity and design parameters of velocity cap, using computational fluid dynamic (CFD) model. A set of engineering design criteria for velocity cap design are derived. The numerical evidence yielded in this study show that the velocity cap should be designed with vertical opening (H_vc) and horizontal shelf (ℓ_vc). The recommended intake opening ratio (O_r) shall be 0.36 V_r^−0.31, where O_r = H_vc/ℓ_vc and V_r =V₀/V_pipe. V_o is the velocity at the intake window and V_pipe is the suction velocity at the intake pipe. The volume ratio (ω_r) between the velocity cap (ω_vc) and intake tower (ω_IT) is recommended at 0.11 V_r^−1.23. The positive outlooks that yielded from this study can be served as a design reference for velocity cap to mitigate the detrimental impacts from the existing intake structure. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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21 pages, 9660 KiB

Open AccessArticle

Three-Dimensional Fluid–Structure Interaction Case Study on Elastic Beam

by Mahdi Tabatabaei Malazi, Emir Taha Eren, Jing Luo, Shuo Mi and Galip Temir

J. Mar. Sci. Eng. 2020, 8(9), 714; https://doi.org/10.3390/jmse8090714 - 15 Sep 2020

Cited by 22 | Viewed by 5111

Abstract

A three-dimensional T-shaped flexible beam deformation was investigated using model experiments and numerical simulations. In the experiment, a beam was placed in a recirculating water channel with a steady uniform flow in the inlet. A high-speed camera system (HSC) was utilized to record [...] Read more.

A three-dimensional T-shaped flexible beam deformation was investigated using model experiments and numerical simulations. In the experiment, a beam was placed in a recirculating water channel with a steady uniform flow in the inlet. A high-speed camera system (HSC) was utilized to record the T-shaped flexible beam deformation in the cross-flow direction. In addition, a two-way fluid-structure interaction (FSI) numerical method was employed to simulate the deformation of the T-shaped flexible beam. A system coupling was used for conjoining the fluid and solid domain. The dynamic mesh method was used for recreating the mesh. After the validation of the three-dimensional numerical T-shaped flexible solid beam with the HSC results, deformation and stress were calculated for different Reynolds numbers. This study exhibited that the deformation of the T-shaped flexible beam increases by nearly 90% when the velocity is changed from 0.25 to 0.35 m/s, whereas deformation of the T-shaped flexible beam decreases by nearly 63% when the velocity is varied from 0.25 to 0.15 m/s. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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19 pages, 6536 KiB

Open AccessArticle

Numerical Simulation of a Polar Ship Moving in Level Ice Based on a One-Way Coupling Method

by Bao-Yu Ni, Zi-Wang Chen, Kai Zhong, Xin-Ang Li and Yan-Zhuo Xue

J. Mar. Sci. Eng. 2020, 8(9), 692; https://doi.org/10.3390/jmse8090692 - 7 Sep 2020

Cited by 39 | Viewed by 3775

Abstract

In most previous ice–ship interaction studies involving fluid effects, ice was taken as unbreakable. Building breakable level ice on water domain is still a big challenge in numerical simulation. This paper overcomes this difficulty and presents a numerical modeling of a ship moving [...] Read more.

In most previous ice–ship interaction studies involving fluid effects, ice was taken as unbreakable. Building breakable level ice on water domain is still a big challenge in numerical simulation. This paper overcomes this difficulty and presents a numerical modeling of a ship moving in level ice on the water by using a one-way CFD-DEM (computational fluid dynamics-discrete element method) coupling method. The detailed numerical processes and techniques are introduced. The ice crack propagation process including radial and circular cracks have been observed. Numerical results are compared with previous experimental data and good agreement has been achieved. The results show that water resistance is an order of magnitude smaller than ice resistance during the ice-breaking process. Ice resistance shows strong oscillation along with ice failure process, which are affected by ship speed and ice thickness significantly. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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25 pages, 9475 KiB

Open AccessArticle

Computational Model for Simulation of Lifeboat Free-Fall during Its Launching from Ship in Rough Seas

by Shaoyang Qiu, Hongxiang Ren and Haijiang Li

J. Mar. Sci. Eng. 2020, 8(9), 631; https://doi.org/10.3390/jmse8090631 - 20 Aug 2020

Cited by 15 | Viewed by 3570

Abstract

In order to improve the accuracy of the freefall of lifeboat motion simulation in a ship life-saving simulation training system, a mathematical model using the strip theory and Kane’s method is established for the freefall of the lifeboat into the water from a [...] Read more.

In order to improve the accuracy of the freefall of lifeboat motion simulation in a ship life-saving simulation training system, a mathematical model using the strip theory and Kane’s method is established for the freefall of the lifeboat into the water from a ship. With the boat moving on a skid, the model of the ship’s maneuvering mathematical group (MMG) is used to model the motion of the ship in the waves. Based on the formula of elasticity and friction theory, the forces of the skid acting on the boat are calculated. When the boat enters the water, according to the analytical solution theory of slamming, the slamming force of water entry is solved. The simulation experiments are carried out by the established model. The results of the numerical simulation are compared with the calculation results of the hydrodynamics software Star CCM+ at water entry under initial condition A in the paper. The position and velocity of the center of gravity of the boat, the angle, and velocity and acceleration of pitch calculated by the two methods are in good agreement. There is a little difference between the values of translation acceleration calculated by the two methods, which is acceptable. This shows that our numerical algorithm has good accuracy. A qualitative analysis is performed to find the safe point of water entry under the condition of different wave heights and two situations of a ship encountering waves. Finally, the model is applied to the ship life-saving training system. The model can meet the system requirements and improve the accuracy of the simulation. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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22 pages, 9777 KiB

Open AccessArticle

Experimental Investigation on Vortex-Induced Vibration of a Flexible Pipe under Higher Mode in an Oscillatory Flow

by Haojie Ren, Mengmeng Zhang, Jingyun Cheng, Peimin Cao, Yuwang Xu, Shixiao Fu and Chang Liu

J. Mar. Sci. Eng. 2020, 8(6), 408; https://doi.org/10.3390/jmse8060408 - 4 Jun 2020

Cited by 6 | Viewed by 3294

Abstract

Different from the previous studies of the vortex-induced vibration (VIV) dominated by first mode of flexible pipe in an oscillatory flow, the features of a higher mode dominated are experimentally investigated in the ocean basin. The flexible pipe is forced to harmonically oscillate [...] Read more.

Different from the previous studies of the vortex-induced vibration (VIV) dominated by first mode of flexible pipe in an oscillatory flow, the features of a higher mode dominated are experimentally investigated in the ocean basin. The flexible pipe is forced to harmonically oscillate with different combinations of a period and amplitude. The design dominant mode consists of first and second modes under the maximum reduced velocity (V_R) of approximately 5.5 with a KC number ranging from 22 to 165. The VIV responses between only the excited first mode and the excited higher mode are compared and studied using displacement reconstruction and wavelet transform methods. The discrepancies of spatial and temporal response between smaller and larger KC numbers (KC = 56 and 121) are first observed. The strong alternate mode dominance and lock-in phenomena occur in the case of larger KC numbers, while they cannot be observed in the case of smaller KC numbers under higher modes. The VIV dominant frequency in the in-line (IL) direction is found to be always triple the oscillatory flow frequency and not twice that in the cross flow (CF) direction. The dominant frequency in the CF direction can be predicted by the Strouhal law, and the Strouhal number is approximately 0.18 under V_R = 5.5, which is not affected by the excited mode. Moreover, differences of response motion trajectory are also revealed in this paper. The present work improves the basic understanding of vessel motion induced VIV and provides helpful references for developing prediction methods of VIV in an oscillatory flow. Full article

(This article belongs to the Special Issue Fluid/Structure Interactions)

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