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Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications

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A special issue of Machines (ISSN 2075-1702). This special issue belongs to the section "Machine Design and Theory".

Deadline for manuscript submissions: 30 September 2026 | Viewed by 7362

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Special Issue Editors

Dr. Yandong Gu

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Guest Editor

College of Hydraulic Science and Engineering, Yangzhou University, Yangzhou, China
Interests: impeller pumps; rotor–stator cavity; fluid lubrication; unsteady flow; hydraulic design
Special Issues, Collections and Topics in MDPI journals

Dr. Christopher Stephen

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Guest Editor

Deep Sea Technologies, National Institute of Ocean Technology, Chennai 600100, Tamil Nadu, India
Interests: impeller pumps; cavitation; computational fluid dynamics; variable ballast system

Dr. Leilei Ji

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Guest Editor

National Research Center for Pumps and Systems, Jiangsu University, Zhenjiang, China
Interests: fluid machinery design and optimization; computational fluid dynamics (CFD); cavitation of pump; rotating stall of mixed-flow pump; transient characteristics during the startup period; PIV measurement
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Guoyi Peng

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Guest Editor

College of Engineering, Nihon University, Koriyama 963-8643, Japan
Interests: water jet; cavitation; multiphase flow; fluid machinery

Special Issue Information

Dear Colleagues,

Fluid machinery components, such as pumps, water turbines, and marine propellers, play a crucial role in optimizing the efficiency and functionality of various systems. However, design methods for such systems and internal flow studies continue to face numerous challenges, including improving their overall efficiency under diverse operating conditions, understanding multiphase flow mechanisms, and ensuring the stability of bearing–rotor systems. By employing innovative design approaches and advanced research techniques, we can foster the development of fluid machinery and deepen our understanding of the intricate flows encountered in these systems.

We invite scholars and researchers to submit their contributions to our Special Issue ”Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications”. Topics of interest include, but are not limited to, the following:

Novel designs for enhancing the performance of fluid machinery;
Innovative studies on multiphase flow in fluid machinery;
Investigations into bearing–rotor systems in fluid machinery.

We welcome original research articles, reviews, and case studies that address these critical areas, and invite authors to join us in improving the performance of hydraulic machinery through cutting-edge research and development.

Dr. Yandong Gu
Dr. Christopher Stephen
Dr. Leilei Ji
Prof. Dr. Guoyi Peng
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Machines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

fluid machinery
pump
bearing–rotor systems
multiphase flow
water turbine performance
Computational Fluid Dynamics (CFD)
fluid-structure interaction

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Published Papers (9 papers)

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Research

29 pages, 23263 KB

Open AccessArticle

Hydraulic Characteristics of Large-Scale Vertical Mixed-Pump Device Under Pump as Turbine (PAT) Mode Applying Chaos Theory

by Can Luo, Kangzhu Jing, Wei Zhang, Ruimin Cai, Li Cheng, Chenzhi Xia, Bowen Zhang and Baojun Zhao

Machines 2026, 14(5), 556; https://doi.org/10.3390/machines14050556 (registering DOI) - 15 May 2026

Viewed by 134

Abstract

As an important option for energy storage projects, pumping stations can also generate electricity when the upstream has surplus water and the pump system operates as a turbine (PAT mode). When it switches from pump mode to PAT mode, the pump operation state changes significantly. This study adopts a numerical simulation to investigate the flow characteristics, time-frequency domain performance and chaotic features of pressure pulsation in a vertical mixed-flow pump device when it operates in different PAT modes. The results show that, when the pump operates in PAT mode, the flow in the straight passage remains smooth, but it deteriorates in the elbow-shaped draft tube, such as developing a spiral stream in the straight section, a disordered stream in the elbow section, and vortexes and flow separation at the beginning of the diffuser section, but it gradually becomes smooth after passing through the diffuser section. Under low-head PAT conditions, circumferential circulation cross flow occurs at the impeller inlet, reducing energy conversion efficiency. Under all PAT conditions, the flow on the blade surface near the hub is stable, but obvious vortexes happen near the shroud. As the head increases, the small-scale vortexes disappear on the mid-blade surface, and the flow becomes smoother on the blade surface near the shroud of the impeller. Except at the impeller outlet, pressure pulsation of the monitoring probes exhibits clear periodicity, with dominant frequencies corresponding to the rotational frequency, and its amplitudes decreasing from shroud to hub. Pressure pulsation under all PAT conditions is chaotic, and phase trajectories exhibit ring-shaped structures consisting of the ring circle and the ring surface. Differences in the circle spacing, size, and spatial position of the ring circle phase locus and ring surface phase locus are observed, and these variations are closely related to the PAT conditions. A correlative relationship exists between the chaotic correlation dimension and flow performance, which is of great significance for the condition monitoring and fault diagnosis of pump units. These findings not only enrich the theoretical research on the PAT mode of pumps, but also provide a reference for similar engineering applications and offer new insights into condition monitoring of hydraulic machinery. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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20 pages, 6820 KB

Open AccessArticle

Effects of Radial Clearance Between Rotor and Casing on Flow Characteristics in a Centrifugal Pump

by Junjie Bian, Yandong Gu, Qiyuan Zhu and Weigang Lu

Machines 2026, 14(4), 438; https://doi.org/10.3390/machines14040438 - 15 Apr 2026

Viewed by 377

Abstract

The electrification of the automotive industry and the lightweighting of aerospace equipment demand high-efficiency centrifugal pumps for compact spaces. A novel centrifugal pump incorporates an integrated impeller-motor rotor design, achieving a more compact footprint and higher power density. However, research is scarce on the radial clearance between the rotor and casing. This study presents a comprehensive investigation of the internal flow dynamics, combining numerical simulations with experimental validation. A significant reduction in fluctuation amplitude for pump efficiency, head coefficient, and frictional loss rate occurs when the clearance ranges from 1.0 to 1.5 mm. Within clearances of 0.75 to 1.5 mm, complex vortex systems emerge in the radial clearance, inducing diverse circumferential high-speed zones. Pressure fluctuations within the radial clearance are predominantly governed by the blade passing frequency. At a clearance of 1.5 mm, the rotational harmonic amplitude at monitoring points exceeds the blade passing frequency amplitude by a factor of 1.9, while the average pressure fluctuation intensity at other points increases significantly by 36.9%. An optimal clearance of 1.25 mm achieves a balance between flow characteristics and energy consumption. This research provides practical insights for optimizing pump energy performance and operational stability. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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17 pages, 3940 KB

Open AccessArticle

Unsteady Internal Flow and Cavitation Characteristics of a Hydraulic Dynamometer for Measuring High-Power Gas Turbines

by Ye Yuan, Zhenyang Liu and Qirui Chen

Machines 2026, 14(3), 342; https://doi.org/10.3390/machines14030342 - 18 Mar 2026

Viewed by 359

Abstract

Hydraulic dynamometer is the key equipment to measure the dynamic performance of high-power gas turbines and steam, with its internal flow characteristics directly influencing measurement accuracy and service life. This paper focuses on the power absorption performance and internal flow characteristics of a hydraulic dynamometer with perforated-disk rotor. A hydraulic test platform is established to measure the power absorption performance of megawatt-level hydraulic dynamometers. When the rotor speed reaches a certain value under the full-water condition, the power absorption of the hydraulic dynamometer reaches its limit. Numerical simulations are applied to study the internal flow characteristics and cavitation evolution features of the perforated-disk-type hydraulic dynamometer. The flow within the outermost rotor pores is the primary factor influencing unsteady flow behaviour, with dynamic–static interference playing a key role in inducing flow excitation. Moreover, cavitation mainly occurs in the flow passages of the end rotor and the outermost flow pores of the middle rotor, where the development and collapse of cavitation bubbles lead to flow instability. As the rotation speed decreases, the power absorption performance significantly decreases under cavitation conditions. These findings provide a theoretical basis for the structural optimization and engineering application of high-power hydraulic dynamometers. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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19 pages, 9452 KB

Open AccessArticle

Numerical Validation of a New Nonlinear Partially Averaged Navier–Stokes Model for Simulating Curved Flows

by Benqing Liu, Guoliang Zhai, Xinyu Zhang, Li Cheng and Jiaxing Lu

Machines 2026, 14(2), 167; https://doi.org/10.3390/machines14020167 - 2 Feb 2026

Viewed by 492

Abstract

To address the insufficient near-wall prediction capability of the traditional Partially Averaged Navier–Stokes (PANS) model in simulating curvature flows, a new nonlinear PANS model with near-wall correction was developed in this study. The model, referred to as the CLS PANS model, is constructed based on Craft’s nonlinear stress formulation and incorporates additional dissipation source and length-scale correction terms to enhance accuracy in curved, rotating, and separated flow fields. To evaluate its applicability and reliability, the new nonlinear PANS model was applied to three representative cases: Taylor–Couette flow, flow past a circular cylinder, and internal flow in a centrifugal pump. Numerical results were systematically compared with experimental data, Direct Numerical Simulation (DNS) results, and results from conventional Reynolds-Averaged Navier–Stokes and k-ε PANS models. The results show that the new nonlinear PANS model can accurately predict complex flow structures such as Taylor vortices and herringbone streaks with lower computational cost, demonstrating improved scale-resolving capability and near-wall performance. For flow past a circular cylinder, the predicted drag coefficient, Strouhal number, and velocity distribution in the wake agree well with experiments. In the centrifugal pump case, the model effectively captured the low-speed and separated flow regions near the blade pressure surfaces, yielding results consistent with experimental observations. Overall, the new nonlinear PANS model achieves a favorable balance between accuracy and efficiency and exhibits strong potential for simulating curvature- and rotation-dominated turbulent flows. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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19 pages, 8241 KB

Open AccessArticle

Prediction of Component Erosion in a Francis Turbine Based on Sediment Particle Size

by Bingning Chen, Yan Jin, Ying Xue, Haojie Liang and Fangping Tang

Machines 2025, 13(11), 1030; https://doi.org/10.3390/machines13111030 - 7 Nov 2025

Cited by 3 | Viewed by 695

Abstract

Erosion caused by sediment-laden flow significantly affects the efficiency and durability of Francis turbines. In this study, the Euler–Lagrange multi-phase flow model was employed to simulate solid-liquid two-phase flow with different sediment particle sizes to analyze erosion characteristics in turbine components. The results show that the maximum erosion rate of the runner blades is positively correlated with particle impact velocity, confirming that impact velocity is the dominant factor influencing local material removal. The total erosion rate of the runner blades, guide vanes, and draft tube corresponds closely with vorticity, indicating that vortex-induced flow separation accelerates particle–wall collisions and intensifies erosion. Both vorticity and erosion exhibit a nonlinear variation with particle size, reaching a minimum at 0.05 mm. These findings establish clear qualitative and quantitative relationships between erosion and key flow parameters, providing theoretical guidance for understanding and mitigating sediment-induced wear in Francis turbines. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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26 pages, 6597 KB

Open AccessArticle

Analysis of Flow Characteristics in a Hydrogen Circulation Pump Featuring a Variable Radius Circular Arc

by Jiankang Lu, Zhengdian Xu, Changdong Wan and Renrui Wang

Machines 2025, 13(9), 869; https://doi.org/10.3390/machines13090869 - 18 Sep 2025

Viewed by 952

Abstract

This study proposes a novel variable-radius arc rotor, developed based on the conventional arc rotor, for application in a hydrogen circulation pump. Numerical simulations are conducted to analyze and compare the flow characteristics of the optimized rotor with those of the baseline rotor. Results show that the optimized rotor increases outlet mass flow rates by over 15%; however, it has little effect on pressure pulsation, indicating limited influence on flow stability. Flow field analysis reveals that the optimized rotor promotes a more stable and streamlined internal velocity distribution, suppressing localized disturbances and vortices that are prevalent with the baseline rotor. Furthermore, assessments of turbulent kinetic energy (TKE) and three-dimensional vortex structures show that the optimized rotor confines high-energy zones to essential areas and facilitates controlled vortex evolution. These effects collectively lead to lower turbulence intensity, reduced energy loss, improved operational efficiency, and enhanced mechanical reliability of the pump. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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18 pages, 3836 KB

Open AccessArticle

Investigation of Blade Root Clearance Flow Effects on Pressure Fluctuations in an Axial Flow Pump

by Fan Meng, Yanjun Li, Mingzhe Li and Chao Ning

Machines 2025, 13(8), 733; https://doi.org/10.3390/machines13080733 - 18 Aug 2025

Cited by 3 | Viewed by 1005

Abstract

This study investigates the leakage vortex influence on pressure pulsation characteristics within a vertical axial flow pump. Three impeller configurations with blade root clearance (δ) of 2.7–8.0 mm were designed to analyze geometric effects on internal flow dynamics. Unsteady RANS simulations predicted flow structures under multiple operating conditions (0.8–1.2Q_des). Fast Fourier Transform (FFT) extracted frequency–domain and time–frequency characteristics of pressure pulsations in critical flow regions. Key results reveal: (1) δ enlargement expands low-pressure zones within blade channels due to enhanced leakage vortices; (2) leading-edge pulsation shows 8.2–11.7% reduction in peak-to-peak amplitude and fundamental frequency magnitude with increasing δ; (3) trailing-edge response exhibits non-monotonic behavior, with maximum amplitude at δ = 5.0 mm (42.2% increase at design flow). These findings demonstrate that blade root clearance optimization requires condition-dependent thresholds to balance leakage management and pulsation control. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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26 pages, 16083 KB

Open AccessArticle

Impact of the Magnetic Gap in Submerged Axial Flux Motors on Centrifugal Pump Hydraulic Performance and Internal Flow

by Qiyuan Zhu, Yandong Gu and Junjie Bian

Machines 2025, 13(8), 721; https://doi.org/10.3390/machines13080721 - 13 Aug 2025

Cited by 2 | Viewed by 1514

Abstract

The integration of axial flux motors into canned motor pumps offers a promising approach to overcome the efficiency and size limitations of traditional designs, particularly in critical sectors like aerospace. However, the hydrodynamics in magnetic gap between the stator and rotor are poorly understood. This study investigates the effect of magnetic gap on performance and internal flow. Six magnetic gap schemes are developed, ranging from 0.2 to 1.2 mm. Numerical simulations are conducted, and simulation results showed good agreement with experimental data. The magnetic gap exhibits a non-linear effect on performance. The peak head coefficient occurs at a 0.4 mm gap and maximum efficiency at 1.0 mm. At a 0.2 mm gap, strong viscous shear forces increase disk friction loss and create high-vorticity flow. As the gap widens, flow transitions from viscosity-dominated to inertia-dominated, leading to a more ordered flow structure. The blade passing frequency is the dominant frequency. For a gap of 0.8 mm, the pressure fluctuation intensity is lowest. By analyzing performance, head coefficient, velocity, vorticity, entropy production, and pressure fluctuations, a gap of 0.8 mm is identified as the optimal design. This study provides critical guidance for optimizing the design of axial flux canned motor pumps. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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16 pages, 10446 KB

Open AccessArticle

Transient Vortex Dynamics in Tip Clearance Flow of a Novel Dishwasher Pump

by Chao Ning, Yalin Li, Haichao Sun, Yue Wang and Fan Meng

Machines 2025, 13(8), 681; https://doi.org/10.3390/machines13080681 - 2 Aug 2025

Cited by 1 | Viewed by 923

Abstract

Blade tip leakage vortex (TLV) is a critical phenomenon in hydraulic machinery, which can significantly affect the internal flow characteristics and deteriorate the hydraulic performance. In this paper, the blade tip leakage flow and TLV characteristics in a novel dishwasher pump were investigated. The correlation between the vorticity distribution in various directions and the leakage vortices was established within a rotating coordinate system. The results show that the TLV in a composite impeller can be categorized into initial and secondary leakage vortices. The initial leakage vortex originates from the evolution of two corner vortices that initially form at different locations within the blade tip clearance. This vortex induces pressure fluctuations at the impeller inlet; its shedding is identified as the primary contributor to localized energy loss within the flow passage. These findings provide insights into TLVs in complex pump geometries and provide solutions for future pump optimization strategies. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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