Journal of Marine Science and Engineering

Research

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15 pages, 5881 KiB

Open AccessArticle

Experimental Study on the Classification and Evolution of the Tip Cavitation Morphology in Axial Waterjet Pumps with Two Different Blade Numbers

by Xi Shen, Haoran Wu, Gang Yang, Rui Tang, Chenxin Chang, Bin Xu, Suben Lin and Desheng Zhang

J. Mar. Sci. Eng. 2024, 12(11), 1898; https://doi.org/10.3390/jmse12111898 - 23 Oct 2024

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Abstract

Tip leakage flow and induced unstable cavitation can significantly damage the performance of axial waterjet pumps. This study investigated the impact of blade numbers on cavitating conditions in an axial waterjet pump by conducting tests of performance characteristics and high-speed photography experiments on [...] Read more.

Tip leakage flow and induced unstable cavitation can significantly damage the performance of axial waterjet pumps. This study investigated the impact of blade numbers on cavitating conditions in an axial waterjet pump by conducting tests of performance characteristics and high-speed photography experiments on three-blade and four-blade impellers. The results showed that the critical cavitation number σ_c of the three-blade impeller was larger, while the four-blade impeller flow pattern deteriorated more rapidly after σ_c. Various cavitation structures in the tip region were observed under different conditions, including clearance cavitation, shear layer cavitation, tip leakage vortex cavitation, and suction-side-perpendicular cavitating vortices (SSPCVs). Tip cavitation maps of the test impellers were drawn based on the flow rate coefficient and cavitation number variation. The three-blade impeller exhibited a wider range of severe cavitation, particularly with an increased occurrence of SSPCVs. With the cavitation number and flow rate coefficient decreased, the SSPCV generated from triangular cavitation cloud shedding presented an increased trend in scale and quantity. Conversely, in the case of the four-blade impeller, SSPCVs were often disrupted by the adjacent blade during migration and interfered with the tip cavitation in the neighboring flow passage. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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21 pages, 10721 KiB

Open AccessArticle

Construction of Solid-Liquid Two-Phase Flow and Wear Rate Prediction Model in Multiphase Pump Based on Mixture Model-Discrete Phase Model Combination Method

by Xin Guo, Guangtai Shi, Yexiang Xiao, Hongqiang Chai, Wenjuan Lv and Jie Fu

J. Mar. Sci. Eng. 2024, 12(10), 1773; https://doi.org/10.3390/jmse12101773 - 6 Oct 2024

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Abstract

Blade wear is the critical problem in the operation of multiphase pump. This paper presents a numerical study of the multiphase flow of multiphase pump. The trajectory of particles in the pump is calculated by the discrete phase model. Then, the simulation results [...] Read more.

Blade wear is the critical problem in the operation of multiphase pump. This paper presents a numerical study of the multiphase flow of multiphase pump. The trajectory of particles in the pump is calculated by the discrete phase model. Then, the simulation results are compared with the model test results of the pump to verify the correctness of the simulation method. The results show that the particles in the impeller domain are mainly near the hub, and the particles in the diffuser domain form a agglomerated area in the middle of the flow channel. The average wear rate of the impeller is more affected by the particle size than that of the diffuser. The maximum wear rate of blade surface increases first and then decreases with the increase of particle size. According to the wear data under different particle sizes, the regression model between particle size and wear rate is fitted to predict the wear of mixed transport pump in actual operation. The research results have important reference value for the prediction of the wear performance of the multiphase pump. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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16 pages, 10922 KiB

Open AccessArticle

Pressure Fluctuation Characteristics of a Pump-Turbine in the Hump Area under Different Flow Conditions

by Kai Zheng, Liu Chen, Shaocheng Ren, Wei Xiao, Yexiang Xiao, Anant Kumar Rai, Guangtai Shi and Zhengkai Hao

J. Mar. Sci. Eng. 2024, 12(9), 1654; https://doi.org/10.3390/jmse12091654 - 14 Sep 2024

Viewed by 782

Abstract

During the operation of a reversible pump-turbine, a hump area can easily appear under the pump condition, which will greatly affect the performance of a storage unit, with pressure pulsation being the key factor for the stable operation of a pump-turbine. Therefore, in [...] Read more.

During the operation of a reversible pump-turbine, a hump area can easily appear under the pump condition, which will greatly affect the performance of a storage unit, with pressure pulsation being the key factor for the stable operation of a pump-turbine. Therefore, in order to explore the pressure pulsation characteristics of each flow component in the hump area, this paper first compared the full characteristics of the model test under different working conditions, and then it analyzed the pressure pulsation characteristics. By analyzing the pressure pulsation characteristics in the unit’s flow component under different flow rates in the hump area, the pulsation rule of a pump-turbine running in the hump area was revealed. It was found that the peak-to-peak value of the draft tube in the hump area was the smallest under the optimal flow condition, and the peak-to-peak value increased along the flow direction, with the rotor and stator interaction (RSI) effects being continuously enhanced. When away from the runner basin, the influence of RSI gradually weakened after leaving the runner. No low frequency was found in the optimal traffic. The peak-to-peak value of the low flow condition increased compared with the optimal flow condition, and the distribution was not uniform. The main frequency of the whole basin was relatively complex, indicating that the flow of water was unstable in the condition of partial load, resulting in the hump area during the unit operation. The research results can provide a theoretical reference for improving the stability of pump-turbines. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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26 pages, 16674 KiB

Open AccessArticle

A Study of the Relationship between Sand Movement and Flow Field Distribution and Wear Causes in a Multiphase Pump

by Xin Guo, Guangtai Shi, Yexiang Xiao and Xunyun Ye

J. Mar. Sci. Eng. 2024, 12(7), 1203; https://doi.org/10.3390/jmse12071203 - 17 Jul 2024

Cited by 1 | Viewed by 913

Abstract

The Rosin–Rammler function is used in this paper to model the diameter distribution of sand particles. It investigates the characteristics of sand distribution and identifies the primary factors contributing to wear on flow components in a blade-type multiphase pump, considering varying particle sizes. [...] Read more.

The Rosin–Rammler function is used in this paper to model the diameter distribution of sand particles. It investigates the characteristics of sand distribution and identifies the primary factors contributing to wear on flow components in a blade-type multiphase pump, considering varying particle sizes. The result of research shows that the blade head of the impeller and the middle section of the flow passage in the diffuser domain represent primary areas prone to sand particle accumulation. The concentration of sand particles within the diffuser surpasses that within the impeller, yet wear severity and extent are more pronounced in the impeller domain compared to the diffuser domain. Meanwhile, the movement trajectory of sand particles is linked to both shear flow and vortex flow. The wear of the front section of the impeller blade is more severe than the second half. On the pressure surface of the blade, particle Reynolds number emerges as a primary factor influencing wear, while on the suction surface, sand particle concentration plays a dominant role in determining wear. The particle concentration in the diffuser domain is the primary factor influencing wear on both the suction and pressure surfaces. The wear rate in the impeller is primarily influenced by the sand particle Reynolds number, whereas the wear rate in the diffuser domain is affected by a combination of sand particle diameter, sand particle concentration, and sand particle Reynolds number. The research findings possess significant engineering value in terms of enhancing the operational lifespan of multiphase pumps. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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20 pages, 22242 KiB

Open AccessArticle

Estimation of Significant Wave Height Using Wave-Radar Images

by Jae-Hoon Lee, Yoon-Seo Nam, Jaehak Lee, Yuming Liu and Yonghwan Kim

J. Mar. Sci. Eng. 2024, 12(7), 1134; https://doi.org/10.3390/jmse12071134 - 5 Jul 2024

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Abstract

Characteristics of random ocean waves have been measured by different devices, and X-band marine radar is one of the typical devices. This study proposes an enhanced methodology for estimating the significant wave height of ocean waves through the analysis of X-band radar images, [...] Read more.

Characteristics of random ocean waves have been measured by different devices, and X-band marine radar is one of the typical devices. This study proposes an enhanced methodology for estimating the significant wave height of ocean waves through the analysis of X-band radar images, particularly leveraging the shadowing characteristics inherent within radar images. The enhancement of the shadowing-based algorithm is achieved by incorporating three different key physical properties of ocean waves. These include the spatial autocorrelation function (SACF) in the Smith function, the orthogonal property of mean surface slopes, and the relationship of high-order spectral moments. The enhanced algorithm is complementarily integrated with fast Fourier transform (FFT)-based spectral analysis, facilitating the determination of significant wave height without the necessity for supplementary reference measurements. Numerical tests have been conducted using synthetic and real radar images corresponding to various sea states to validate the accuracy and reliability of the proposed methodology. The results demonstrate that the proposed techniques consistently improve the estimation accuracy of significant wave heights for both synthetic and real radar images. Even though the measured real radar images used for validation are not exhaustive in terms of the amount of dataset and range of sea state severity, considering that the proposed technique is in its early development stage, it is inspiring that its effectiveness and physical validity have been demonstrated through the present study. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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14 pages, 6505 KiB

Open AccessArticle

Effect of Tip Clearance on Force Characteristics of Helical Axial-Flow Blade Pumps under Cavitation Conditions

by Haigang Wen, Luyao Li, Guangtai Shi, Haijun Ma and Xiaodong Peng

J. Mar. Sci. Eng. 2023, 11(12), 2299; https://doi.org/10.3390/jmse11122299 - 4 Dec 2023

Viewed by 1040

Abstract

A spiral axial-flow blade pump (SABP), as the core piece of equipment in the oil and natural gas closed-gathering and transportation process, can not only transport gas–liquid mixtures with a high gas content, but can also transport gas–liquid–solid mixtures containing small amounts of [...] Read more.

A spiral axial-flow blade pump (SABP), as the core piece of equipment in the oil and natural gas closed-gathering and transportation process, can not only transport gas–liquid mixtures with a high gas content, but can also transport gas–liquid–solid mixtures containing small amounts of sand. However, due to the complexity of the distribution of transport media groups and the uncertainty of internal flow processes, large vortices often appear in the passage of the pumps, and the existence of vortices can easily induce the occurrence of pump cavitations. In the present work, a self-developed SABP was taken as the research object, and the cavitation performance of the SABP was numerically calculated. The pressure load variation under different tip clearances and different cavitation stages was analyzed, and the characteristics of the axial and radial forces were also analyzed in detail. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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24 pages, 6805 KiB

Open AccessArticle

Research on the Hydrodynamic Noise Characteristics of a Mixed-Flow Pump

by Qiaoyue Yang, Wei Li, Leilei Ji, Weidong Shi, Wei Pu, Yu Long and Xinrui He

J. Mar. Sci. Eng. 2023, 11(12), 2209; https://doi.org/10.3390/jmse11122209 - 21 Nov 2023

Cited by 2 | Viewed by 1341

Abstract

This study presents a comprehensive investigation of the internal noise characteristics of a mixed-flow pump by combining computational fluid dynamics (CFD) and computational acoustics. The turbulent flow field of the pump is simulated using the unsteady SST k-ω turbulence model in CFD. The [...] Read more.

This study presents a comprehensive investigation of the internal noise characteristics of a mixed-flow pump by combining computational fluid dynamics (CFD) and computational acoustics. The turbulent flow field of the pump is simulated using the unsteady SST k-ω turbulence model in CFD. The contributions of the volute, guide vanes, and impeller to the internal noise are analyzed and compared using the Lighthill theory, FW-H formula, and LMS Virtual Lab software for acoustic simulation. The research findings indicate that the energy of pressure fluctuations in the mixed-flow pump is predominantly concentrated at the blade passing frequency and its low-frequency harmonics. This suggests that the internal noise is mainly in the low-frequency range, with higher energy at the blade passing frequency and its harmonics. Under the 0.6Q_des flow condition, the flow inside the pump becomes more complex, resulting in higher sound pressure levels and sound power levels compared to higher flow conditions. However, for flow conditions ranging from 0.8Q_des to 1.2Q_des, the sound pressure levels gradually increase with increasing flow rate, with the sound pressure level at 1.0Q_des being nearly identical to that at 1.2Q_des. The analysis of sound power level spectra at different flow rates reveals that the distribution characteristics of internal vortex structures directly impact the hydrodynamic noise inside the mixed-flow pump. These research findings provide a significant theoretical basis for noise control in mixed-flow pumps. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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Review

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21 pages, 345 KiB

Open AccessReview

Data-Driven Modal Decomposition Methods as Feature Detection Techniques for Flow Fields in Hydraulic Machinery: A Mini Review

by Bin Xu, Liwen Zhang, Weibin Zhang, Yilin Deng and Teck Neng Wong

J. Mar. Sci. Eng. 2024, 12(5), 813; https://doi.org/10.3390/jmse12050813 - 13 May 2024

Cited by 2 | Viewed by 1103

Abstract

Cavitation is a quasi-periodic process, and its non-stationarity leads to increasingly complex flow field structures. On the other hand, characterizing the flow field with greater precision has become increasingly feasible. However, accurately and effectively extracting the most representative vibration modes and spatial structures [...] Read more.

Cavitation is a quasi-periodic process, and its non-stationarity leads to increasingly complex flow field structures. On the other hand, characterizing the flow field with greater precision has become increasingly feasible. However, accurately and effectively extracting the most representative vibration modes and spatial structures from these vast amounts of data has become a significant challenge. Researchers have proposed data-driven modal decomposition techniques to extract flow field information, which have been widely applied in various fields such as signal processing and fluid dynamics. This paper addresses the application of modal decomposition methods, such as dynamic mode decomposition (DMD), Proper Orthogonal Decomposition (POD), and Spectral Proper Orthogonal Decomposition (SPOD), in cavitation feature detection in hydraulic machinery. It reviews the mathematical principles of these three algorithms and a series of improvements made by researchers since their inception. It also provides examples of the applications of these three algorithms in different hydraulic machinery. Based on this, the future development trends and possible directions for the improvement of modal decomposition methods are discussed. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Simulation of Floating Offshore Structures—2nd Edition)

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