Research

17 pages, 7160 KiB

Open AccessArticle

Study on Wear Characteristics of a Guide Vane Centrifugal Pump Based on CFD–DEM

by Weidong Cao, He Wang and Jian Tang

J. Mar. Sci. Eng. 2024, 12(4), 593; https://doi.org/10.3390/jmse12040593 - 29 Mar 2024

Viewed by 512

Guide vane submersible centrifugal pumps are a kind of submersible pump, and the fluid inside the pump is often mixed with gravel and other impurities during operation, affecting the pump’s operating efficiency and life expectancy. However, past studies on solid–liquid two-phase flow (STF) [...] Read more.

Guide vane submersible centrifugal pumps are a kind of submersible pump, and the fluid inside the pump is often mixed with gravel and other impurities during operation, affecting the pump’s operating efficiency and life expectancy. However, past studies on solid–liquid two-phase flow (STF) and wear characteristics in guided vane centrifugal pumps have been limited to the particle trajectory and wear region distribution. These studies have lacked research on the effect of particles on the fluid flow and the specific amount of wear on the overflow components. Additionally, most of them have used the DPM discrete-phase model, which does not consider the particle–particle and particle–wall interactions. This paper is based on the CFD–DEM method, combined with the Archard wear model. A solid–liquid two-phase flow simulation is carried out for pumps with different particle sizes and particle shapes to analyze the particle movement inside the pump, the wear distribution and average wear amount of the overflow components, and the effect of particles on the turbulent kinetic energy of the fluid. The results show that the particles mainly collide with the leading and trailing edges of the impeller blades and the leading edge of the guide vane blades and form a buildup at the trailing edge of the concave surface of the guide vane blades, resulting in the wear being mainly distributed in these regions. With an increase in particle size and a decrease in sphericity, the average wear on the overflow components increases. The change of particle size directly affects the resistance of the fluid and the structure of the flow field, which has a large impact on the fluid flow pattern and generates large turbulent kinetic energy fluctuations. The shape of the particles only changes the structure of the local flow field, which has a small impact on the fluid flow pattern. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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30 pages, 15059 KiB

Open AccessArticle

Numerical Investigation of the Impacts of Large Particles on the Turbulent Flow and Surface Wear in Series-Connected Bends

by Yuan-Hang Zhang, Xiao-Jie Wang, Xu-Zhen Zhang, Maoukouf Saad and Rui-Jie Zhao

J. Mar. Sci. Eng. 2024, 12(1), 164; https://doi.org/10.3390/jmse12010164 - 15 Jan 2024

Cited by 1 | Viewed by 680

Abstract

The deep sea harbors abundant mineral, oil, and gas resources, making it highly valuable for commercial development, including the extraction of minerals. Due to the relatively large particle size of these minerals, how they interact with fluids is significantly different from that of [...] Read more.

The deep sea harbors abundant mineral, oil, and gas resources, making it highly valuable for commercial development, including the extraction of minerals. Due to the relatively large particle size of these minerals, how they interact with fluids is significantly different from that of small particles. However, there has been limited simulation research on the impacts of large particles (the diameter of particles is at the level of centimeters) on the flow and wear characteristics in bends, because the simulation of the particles at such a size is difficult. Additionally, in the field of deep-sea mining, multiple bends are simultaneously connected in series, and the wear in such bends has garnered increasing attention. Based on an improved CFD-DEM model, this article solved the issue that traditional unresolved CFD-DEM methods cannot accurately simulate large particles in a hydraulic conveying pipe and bend. After validating the accuracy of this model against classical experiments, the paper comprehensively analyzes the modulation effect of large particles on turbulence, and the effects of different particle diameters, particle transport concentrations, and transport velocities on the wear of bends connected serially. Finally, the bends connected serially in various configurations are simulated to study the wear on the bent interior surfaces. Results indicate a pronounced modulation effect of large particles on turbulence at higher transport concentrations; the wear rate in the combined bends does not exhibit a linear correlation with the collision frequency of particles on the wall surface. Furthermore, different configurations of serially connected bends exhibit significant differences in the wear morphology of the second bend. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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27 pages, 21233 KiB

Open AccessArticle

Numerical Analysis on Effect of Structural Parameters on Flow Field and Internal Trajectory in Gas–Steam Ejection Systems

by Bing Liu, Renfeng Li, Xiaohan Chen, Jinlan Gou, Bangming Li and Guigao Le

J. Mar. Sci. Eng. 2023, 11(10), 1937; https://doi.org/10.3390/jmse11101937 - 07 Oct 2023

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Abstract

This paper aims to study the influence of the structure of spray holes and throats on the flow field and the internal trajectory of the gas–steam ejection device. The compressible Navier–Stokes equations, discrete ordinate methods and RNG k-ε turbulence model are [...] Read more.

This paper aims to study the influence of the structure of spray holes and throats on the flow field and the internal trajectory of the gas–steam ejection device. The compressible Navier–Stokes equations, discrete ordinate methods and RNG k-ε turbulence model are utilized to simulate the two-phase flow of the rocket gas with multispecies and the water sprays. The comparison between numerical results and experimental data confirms the accuracy and effectiveness of this model. The simulation analysis on the cases of the ejection process with multiple spray hole diameters, number of spray holes, total spray area, and throat diameter are conducted. The shock wave structure inside the gas–steam ejection device is examined. The simulation results show that, instead of the spray hole diameter and number, the total spray area and secondary nozzle throat diameter are the key factors that affect the flow field and internal trajectory of the gas–steam ejection device. Under the existing spray structure, the maximum number of spray holes is 300 to achieve the stability of the flow field and internal ballistic trajectory of gas–steam ejection devices. By comparing the throat diameters of multiple secondary nozzles, it was found that the minimum throat diameter of the secondary nozzles should be no less than 100 mm. The results could be valuable for the design of gas–steam ejection devices. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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13 pages, 5378 KiB

Open AccessArticle

Study on the Resistance of a Large Pure Car Truck Carrier with Bulbous Bow and Transom Stern

by Xiaoqing Tian, Tianwei Xie, Zhangming Liu, Xianghua Lai, Huachen Pan, Chizhong Wang, Jianxing Leng and M. M. Rahman

J. Mar. Sci. Eng. 2023, 11(10), 1932; https://doi.org/10.3390/jmse11101932 - 07 Oct 2023

Viewed by 783

Abstract

The resistance of a large Pure Car Truck Carrier (PCTC) with a bulbous bow and a transom stern is evaluated in the present paper. Several cases at nine different ship speeds in calm water are simulated and results are compared with the experimental [...] Read more.

The resistance of a large Pure Car Truck Carrier (PCTC) with a bulbous bow and a transom stern is evaluated in the present paper. Several cases at nine different ship speeds in calm water are simulated and results are compared with the experimental measurements. The maximum relative error is 0.93% at a Froude number (Fr) of 0.209. The total resistance coefficient of the ship in calm water shows a parabolic trend with increasing Fr, and it reaches a minimum value at Fr = 0.1794. Furthermore, the cases of the ship in regular waves with six different wavelengths and three wave heights are simulated. It is observed that the total resistance exhibits a quadratic relationship with the wavelength when the wave height is fixed. The wave-making resistance increases with the increase in wave height at any fixed wavelength, and it reaches a maximum value when the wave-length is 1.2 times the ship length (L_pp). Additionally, we also investigated the resistance in three different sea states at four different speeds. When the significant wave height of irregular waves is the same as regular waves, the wave-making resistance under irregular waves is much smaller than that of the regular waves. All of these results indicate that the bulbous bow and transom stern can reduce the wave-making and residuary resistances, which can provide a useful reference for the subsequent design and manufacturing of related ships. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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29 pages, 17732 KiB

Open AccessArticle

Optimization of Guide Vane Centrifugal Pumps Based on Response Surface Methodology and Study of Internal Flow Characteristics

by Weidong Cao, He Wang, Xinyu Yang and Xinyi Leng

J. Mar. Sci. Eng. 2023, 11(10), 1917; https://doi.org/10.3390/jmse11101917 - 04 Oct 2023

Cited by 2 | Viewed by 957

Abstract

The methodologies of computational fluid dynamics (CFD) and response surface method (RSM) were integrated to uncover the optimal correlational framework for intricate hydraulic geometric parameters of guide vane centrifugal pumps. Parameters such as blade number, blade wrap angle, blade outlet angle, and relative [...] Read more.

The methodologies of computational fluid dynamics (CFD) and response surface method (RSM) were integrated to uncover the optimal correlational framework for intricate hydraulic geometric parameters of guide vane centrifugal pumps. Parameters such as blade number, blade wrap angle, blade outlet angle, and relative axial distance between the guide vane and impeller, as well as radial distance, are embraced as optimization design variables. Meanwhile, pump head and efficiency were chosen as responsive variables. An analysis of 46 sets of hydraulic performance data was carried out by using the Box–Behnken experimental design method. Subsequently, response surface approximation models were established between hydraulic parameters and the efficiency, as well as the head. The optimal design point was predicted and a simulation of the hydraulic characteristics for the optimal scheme was conducted; the errors were 0.846% for head and 0.256% for efficiency between the simulation results with predicted results from RSM. The optimized model demonstrates noteworthy enhancements in hydraulic performance in comparison to the original model. By analyzing the internal flow of the optimized model under transient conditions, it was found that, as the internal flow of the flow passage components is relatively disordered at small flow rates, the amplitude of pressure pulsation is affected a lot. At other flow rates, the inside pressure pulsation waveform exhibits pronounced periodicity, and the primary causes of pressure pulsation in various flow components are not the same. Wall dissipation and turbulent dissipation emerge as significant contributors to the entropy generation in this centrifugal pump. The magnitude of entropy generation is correlated with the flow rate and the structural configuration of the pump’s components. High-entropy regions concentrate around the leading and trailing edges of the blades. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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18 pages, 7586 KiB

Open AccessArticle

Wave Characteristics over a Dual Porous Submerged Breakwater Using a Fully Nonlinear Numerical Wave Tank with a Porous Domain

by Eun-Hong Min, Weoncheol Koo and Moo-Hyun Kim

J. Mar. Sci. Eng. 2023, 11(9), 1648; https://doi.org/10.3390/jmse11091648 - 23 Aug 2023

Viewed by 925

Abstract

This study developed a two-dimensional fully nonlinear numerical wave tank (FN-NWT) to examine the nonlinear interaction between waves and dual submerged porous structures. Using the FN-NWT, not only reflection and transmission coefficients, but also wave deformation/force depending on porosity were investigated. The FN-NWT [...] Read more.

This study developed a two-dimensional fully nonlinear numerical wave tank (FN-NWT) to examine the nonlinear interaction between waves and dual submerged porous structures. Using the FN-NWT, not only reflection and transmission coefficients, but also wave deformation/force depending on porosity were investigated. The FN-NWT was developed using the boundary element method (BEM), and consisted of a fluid domain and a porous medium domain. Darcy’s law or the non-Darcy (Forchheimer) flow equation were applied to the flow passing through the porous domain. The wave reflection coefficient of the porous submerged structures agreed well with the given experimental data when using Forchheimer flow boundary conditions. Excessive attenuation of the transmitted wave occurred when Darcy’s condition was employed. The difference in each coefficient due to the spacing of the submerged structure was reduced in the porous structure compared with the non-porous structure. The difference according to the incident wave height was clearly revealed in the transmission coefficient. The developed dual-domain FN-NWT can be applied to investigate the nonlinear interaction between waves and porous structures as a first-cut design tool. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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18 pages, 23296 KiB

Open AccessArticle

Visualization and Parametric Study on Vortex Shedding Suppression of Cylindrical Structures in Offshore Engineering Using Large Eddy Simulation

by Hongwu Zhao and Yeon-Won Lee

J. Mar. Sci. Eng. 2023, 11(5), 1090; https://doi.org/10.3390/jmse11051090 - 22 May 2023

Viewed by 1164

Abstract

Cylindrical structures are widely used in offshore and marine engineering, but they may suffer from vortex-induced vibration under the influence of ocean or wave currents, which can lead to severe fatigue damage. In this study, we applied the open-source software Open-Source Field Operation [...] Read more.

Cylindrical structures are widely used in offshore and marine engineering, but they may suffer from vortex-induced vibration under the influence of ocean or wave currents, which can lead to severe fatigue damage. In this study, we applied the open-source software Open-Source Field Operation and Manipulation (OpenFOAM) to investigate the characteristics of fluid flow around offshore cylindrical structures, taking into account the effect of helical strake parameters, such as pitch and strake number. The aim of this study is to explore the possibility of suppressing vortex shedding with different helical strake parameters. Numerical simulation results demonstrated that attaching a helical strake to the bare cylinder destroyed vortex shedding in offshore cylindrical structures. The vortex visualization showed that the helical strake destroyed the three-dimensional vortex structures. Moreover, the lift coefficient data showed that the vibration frequency of the cylinder decreased after attaching the helical strake, indicating that the vortex-induced vibrations on the wake flow tended to fade. The results suggest that the helical strake is a promising option for suppressing the wake vortex shedding of cylindrical structures in offshore engineering. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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18 pages, 13672 KiB

Open AccessArticle

Numerical Analysis on Water-Exit Process of Submersible Aerial Vehicle under Different Launch Conditions

by Bing Liu, Xiaohan Chen, Enyi Li and Guigao Le

J. Mar. Sci. Eng. 2023, 11(4), 839; https://doi.org/10.3390/jmse11040839 - 15 Apr 2023

Cited by 1 | Viewed by 1356

Abstract

To study the influence of launch conditions and wave interference on the stability of submersible aerial vehicles at the water–air interface, a coupling model for water-exit motion of submersible aerial vehicles was established by using the RNG k-ε turbulence model and VOF method. [...] Read more.

To study the influence of launch conditions and wave interference on the stability of submersible aerial vehicles at the water–air interface, a coupling model for water-exit motion of submersible aerial vehicles was established by using the RNG k-ε turbulence model and VOF method. The water-exit processes of submersible aerial vehicles under different initial inclination angles and velocities were numerically simulated and the effects of initial inclination angle and velocity on the water-exit motion of submersible aerial vehicles were obtained. Based on the response surface function theory, a mathematical model for the motion stability of submersible aerial vehicles at the water–air interface was established, so that the submersible aerial vehicle’s pitch angle and velocity at the end of vehicle’s water-exit process, corresponding to any initial inclination angle and velocity, can be solved. The deviation between the simulated calculation result and the established fitting function model result was 2.7%. The minimum water-exit velocity of submarine aerial vehicles should be greater than 10.8 m/s. The research provides technical support for the trans-media motion stability analysis and hydrodynamic performance design of the submersible aerial vehicle. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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