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Hydrodynamics Science Experiments and Simulations, 2nd Edition

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydraulics and Hydrodynamics".

Deadline for manuscript submissions: closed (25 December 2025) | Viewed by 10374

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Special Issue Editors

Dr. Yonggang Lu

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Guest Editor

School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
Interests: hydroturbine; pump turbine; gas–liquid two-phase flow; solid–liquid two-phase flow; abrasion; CFD
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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
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Dr. Wenwu Zhang

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Guest Editor

College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100191, China
Interests: pumps; gas–liquid two-phase flow; unsteady flow; hydraulic design
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Dr. Yongyao Luo

E-Mail Website
Guest Editor

Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
Interests: hydrodynamics simulation; pump turbine; tidal energy; multi-phase Flow
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Hydrodynamic experiments and simulations play a crucial role in scientific research, enabling us to understand and predict fluid movements and interactions across various environments. This knowledge is essential in fields such as ship design, coastal engineering, and hydraulic engineering. For instance, hydrodynamic simulations allow us to optimize ship designs for improved efficiency and stability, as well as predict and mitigate potential accidents in coastal hydraulic engineering.

The study of hydrodynamics typically encompasses three methods: theoretical analysis, field measurements, and laboratory experiments, along with numerical simulations. Among these, hydrodynamic experiments and simulations are critical for accurately determining key parameters such as the pressure drop and minimum fluidization velocity in gas–solid fluidization. These studies enhance our comprehension of fluid dynamics' complexity and provide vital tools for analyzing and predicting related issues.

In summary, hydrodynamic experiments and simulations are fundamental for understanding and managing fluid behavior in various environments. They equip us with the predictive capabilities and technological improvements necessary to address future challenges effectively.

This Special Issue will cover, but is not limited to, the following topics:

New methods and models for the numerical simulation of hydrodynamics;
Innovative experimental methods and equipment for hydrodynamic studies;
Cavitation, vortex, and multiphase flow in hydraulic machinery;
Hydro, tidal, and ocean energy.

Dr. Yonggang Lu
Dr. Yandong Gu
Dr. Wenwu Zhang
Dr. Yongyao Luo
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. Water is an international peer-reviewed open access semimonthly 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 2600 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

hydrodynamic experiment
hydrodynamic simulation
hydraulic machinery
multiphase flow
hydro energy technology

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Related Special Issue

Hydrodynamics Science Experiments and Simulations, 3rd Edition in Water (2 articles)

Published Papers (8 papers)

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Research

27 pages, 7755 KB

Open AccessArticle

Characterization of a Multi-Diffuser Fine-Bubble Aeration Reactor: Influence of Local Parameters and Hydrodynamics on Oxygen Transfer

by Oscar Prades-Mateu, Guillem Monrós-Andreu, Delia Trifi, Jaume Luis-Gómez, Salvador Torró, Raúl Martínez-Cuenca and Sergio Chiva

Water 2025, 17(24), 3448; https://doi.org/10.3390/w17243448 - 5 Dec 2025

Viewed by 1061

Abstract

Fine-bubble aeration is a core process in wastewater treatment plants (WWTPs). However, the physical mechanisms linking bubble plume hydrodynamics to oxygen transfer performance remain insufficiently quantified under configurations representative of full-scale installations. This study presents a local multi-sensor experimental characterization of a multiple bubble plume system using a 4 × 4 array of commercial membrane diffusers in a pilot-scale aeration tank (2 m³), emulating WWTP diffuser density and geometry. Airflow rate was varied to analyze its effects on mixing and oxygen transfer efficiency. The experimental methodology combines three complementary measurement approaches. Oxygen transfer performance is quantified using a dissolved oxygen probe. Liquid-phase velocity fields are then mapped using Acoustic Doppler Velocimetry (ADV). Finally, local two-phase measurements are obtained using dual-tip Conductivity Probe (CP) arrays, which provide bubble size, bubble velocity, void fraction, and Interfacial Area Concentration (IAC). Based on these observations, a zonal hydrodynamic model is proposed to describe plume interaction, wall-driven recirculation, and the formation of a collective plume core at higher airflows. Quantitatively, the results reveal a 29% reduction in Standard Oxygen Transfer Efficiency (SOTE) between 10 and 40 m³/h, driven by a 41% increase in bubble size and an 18% rise in bubble velocity. Bubble chord length also increased with height, by 33%, 19%, and 15% over 0.8 m for 10, 20, and 40 m³/h, respectively. These trends indicate that increasing airflow enhances turbulent mixing but simultaneously enlarges bubbles and accelerates their ascent, thereby reducing residence time and negatively affecting oxygen transfer. Overall, the validated multiphase datasets and mechanistic insights demonstrate the dominant role of diffuser interaction in dense layouts, supporting improved parameterization and experimental benchmarking of fine-bubble aeration systems in WWTPs. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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24 pages, 30023 KB

Open AccessArticle

Numerical and Experimental Analysis of Internal Flow Characteristics of Four-Way Opposing Diaphragm Pump

by Guangjie Peng, Han Chai, Chengqiang Liu, Kai Zhao, Jianfang Zhang and Hao Chang

Water 2025, 17(21), 3094; https://doi.org/10.3390/w17213094 - 29 Oct 2025

Viewed by 930

Abstract

This study investigates the steady-state behavior of a four-way opposed diaphragm pump. Simulations and experimental results confirm that peak stress locations align with observed damage sites. During the return stroke, diaphragm flipping induces tension at the flow-fixed interface edges, creating stress concentrations that contribute to fatigue and failure. Particle image velocimetry (PIV) shows that, under constant flow, increased voltage enhances umbrella valve opening, accelerates movement, broadens flow distribution, and disrupts symmetry. At 90°, valve-edge velocity exhibits sharp, high-amplitude oscillations and a narrow, elongated return region. Vortices near the valve port interfere with fluid motion, causing pressure fluctuations and potential sealing issues or increased opening resistance. Higher flow rates intensify vortex strength and shift their position, generating diaphragm pressure differentials that alter flow direction and velocity, reducing stability and inducing secondary vortices. Compared to a modified diaphragm, the standard type shows more complex vortex structures, greater flow instability, and dynamic response degradation under identical pressure and varying flow. These fragmented vortices further disrupt flow, affecting pump performance. The findings provide design insights for diaphragm pump optimization. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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24 pages, 9449 KB

Open AccessArticle

Assessing the Hydraulic Parameters of an Open Channel Spillway Through Numerical and Experimental Approaches

by Elaheh Motahari Moghadam, Ali Saeidi, Javier Patarroyo, Alain Rouleau and Meghdad Payan

Water 2025, 17(21), 3059; https://doi.org/10.3390/w17213059 - 25 Oct 2025

Viewed by 1508

Abstract

The effective design and operation of hydraulic structures, particularly open channel spillways, are crucial for water resource management and flood risk reduction in dams. A clear understanding of flow properties, such as velocity fluctuations and discharge, across various depths is essential for optimizing performance. In this study, experimental analysis and numerical simulation using FLOW-3D were combined to investigate the hydraulic parameters of a scaled model of the Romaine IV spillway located in Quebec, Canada. Measurements focused on flow properties, including velocity fluctuations at various discharge rates in specific flow depths, at selected points along the spillway. The numerical model was assessed by reproducing experimental geometry, initial water levels, and boundary conditions, and through sensitivity analyses to ensure accurate flow representation. Comparisons of flow rates of 180, 240, and 340 L/s showed that while simulations with the renormalized group (RNG) turbulence model reliably predicted average velocities, they underestimated maximum values and overestimated minimum values, especially at higher discharges. The results highlight the difficulty of accurately capturing velocity extremes in turbulent flows and the need for further model refinement. This was evident from the 60% discrepancy in minimum velocities observed at the channel center. Despite these discrepancies, the study advances our understanding of spillway performance and identifies avenues to improve the accuracy of numerical modeling in hydraulic engineering. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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18 pages, 1611 KB

Open AccessArticle

Hybrid Decomposition Strategies and Model Combinatorial Optimization for Runoff Prediction

by Wenbin Hu and Xiaohui Yuan

Water 2025, 17(17), 2560; https://doi.org/10.3390/w17172560 - 29 Aug 2025

Cited by 1 | Viewed by 1829

Abstract

Runoff prediction plays a critical role in water resource management and flood mitigation. Traditional runoff prediction methods often rely on single-layer optimization frameworks that process the data without decomposition and employ relatively simple prediction models, leading to suboptimal performance. In this study, a novel two-layer optimization framework is proposed that integrates data decomposition techniques with multi-model combination strategies, establishing a closed-loop feedback mechanism between decomposition and prediction processes. The framework employs the Snow Ablation Optimizer (SAO) to optimize combination weights across both layers. Its adaptive fitness function incorporates three evaluation metrics—Mean Absolute Percentage Error (MAPE), Relative Root Mean Square Error (RRMSE), and Nash–Sutcliffe Efficiency (NSE)—to enable adaptive data processing and intelligent model selection. We validated the framework using observational data from Huangzhuang Hydrological Station in the Hanjiang River Basin. The results demonstrate that, at the decomposition layer, optimal performance was achieved by combining non-decomposition, Singular Spectrum Analysis (SSA), and Complementary Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) (with coefficients 0.4061, 0.6115, and −0.0063), paired with the long short-term memory (LSTM) model. At the prediction layer, the proposed algorithm achieved a 32.84% improvement over the best single decomposition method and a 30.21% improvement over the best single combination optimization approach. These findings confirm the framework’s effectiveness in enhancing runoff data decomposition and optimizing multi-model selection. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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15 pages, 2777 KB

Open AccessArticle

Research on an Underwater Target Classification Method Based on the Spatial–Temporal Characteristics of a Flow Field

by Xinghua Lin, Hang Xu, Hao Wang, Peilong Sun, Enyu Yang and Guozhen Zan

Water 2025, 17(13), 2006; https://doi.org/10.3390/w17132006 - 3 Jul 2025

Cited by 1 | Viewed by 751

Abstract

In order to solve problems such as recognition of blind areas which exist in traditional technology in underwater near-field target sensing, this paper constructs an underwater robot target sensing model based on the fish lateral line sensing mechanism and adopts CFD simulation technology to analyze the perturbation characteristic law of the pressure signal in the flow field around the underwater robot. By extracting the pressure signal following the bionic lateral line on the surface of the underwater robot as the target recognition information, the SVM multi-target recognition model is trained and built to realize the perception and recognition of the structural features and attitude features of the underwater robot. The results show that the structural features and attitude features of the underwater robot can be recognized by using the time-domain waveform structural features and spatially symmetric distribution features of the pressure coefficients, and the recognition accuracy can reach over 90%, which reveals the principle of target feature resolution based on the sideline perception signals of the fish nerve center. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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15 pages, 5321 KB

Open AccessArticle

Acoustic Modal Characteristics of Pump Tower Structures Based on Fluid–Structure Coupling Effects

by Wei Song, Aoyu Xie, Yonggang Lu, Yun Zhao and Zhengwei Wang

Water 2025, 17(13), 1864; https://doi.org/10.3390/w17131864 - 23 Jun 2025

Viewed by 907

Abstract

This study investigated the acoustic modal characteristics of pump tower structures under fluid–structure coupling effects through a finite element analysis. Compared with the dry condition, filling the internal pipelines with liquid causes the first three natural frequencies to decrease by 17.12%, 16.80%, and 19.50%, respectively, while full external immersion (wet mode) further reduces them by 15.60%, 15.10%, and 5.30%. As the liquid level in the surrounding storage tank increases from 0% to 100%, the first-mode frequency falls from 6.07 Hz to 5.13 Hz (a 15.5% reduction), the second-mode from 14.71 Hz to 12.48 Hz (15.1%), and the third-mode from 19.69 Hz to 18.63 Hz (5.5%). Mode-shape distributions remain qualitatively similar across liquid levels, although local deformation magnitudes decrease by up to 21.0% for the first mode and 18.3% for the second mode. These quantitative findings provide a theoretical and technical basis for predicting dynamic responses of pump tower structures in complex fluid environments. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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16 pages, 12973 KB

Open AccessArticle

Study of Inlet Vortex Behavior in Dual-Pump Systems and Its Influence on Pump Operational Instability

by Wei Song, Jilong Lin, Yonggang Lu, Yun Zhao and Zhengwei Wang

Water 2025, 17(12), 1784; https://doi.org/10.3390/w17121784 - 14 Jun 2025

Cited by 1 | Viewed by 1002

Abstract

This study addresses inlet flow distribution and pressure pulsation-induced vibration in LNG dual-pump parallel systems. We investigate an LNG dual-submerged pump tower system. Our approach combines computational fluid dynamics with vortex dynamics theory. We examine inlet flow characteristics under different flow conditions. Pressure pulsation propagation patterns are analyzed. System stability mechanisms are investigated. A 3D model incorporates inducers, impellers, guide vanes, outlet sections, and base structures. The SST k-ω turbulence model and Q-criterion vortex identification reveal key features. Results show minimal head differences during parallel operation. The inlet flow field remains uniform without significant vortices. However, local low-velocity zones beneath the base may cause flow separation at low flows. Pressure pulsations are governed by guide vane rotor–stator interactions. These disturbances propagate backward to impellers and inducers. Outlet sections show asymmetric pressure fluctuations. This asymmetry results from spatial positioning differences. Complex base geometries generate low-intensity vortices. Vortex intensity stabilizes at higher flows. These findings provide theoretical foundations for vibration suppression. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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25 pages, 8681 KB

Open AccessArticle

Numerical Investigation of Subcooled Boiling Flow and Patterns’ Transitions in a High-Heat-Flux Rectangular Small Channel

by Xianyang Wu, Xiao Wang, Yang Liu and Linmin Li

Water 2025, 17(11), 1580; https://doi.org/10.3390/w17111580 - 23 May 2025

Cited by 1 | Viewed by 1729

Abstract

The escalating thermal demands of high-power electronic devices and energy systems necessitate advanced thermal management solutions. Flow boiling in small/micro channels has emerged as a promising approach, yet its practical implementation is hindered by flow instabilities and heat transfer deterioration under high-heat fluxes. This study presents a systematic numerical investigation of subcooled boiling flow and heat transfer in a rectangular small channel under high-heat-flux conditions, employing the VOF method coupled with the Lee phase change model. The increasing heat flux accelerates bubble nucleation and coalescence while reduced mass flux promotes early local slug formation, shifting flow transitions upstream and degrading thermal performance. A local vapor volume fraction threshold of α_ν = 0.2 is identified for the bubbly-to-sweeping flow transition and α_ν = 0.4 for the sweeping-to-churn transition. Furthermore, a novel dimensionless parameter β is proposed to classify dominant flow regimes, with critical β ranges of 12–16 and 24–32 corresponding to the two transitions, respectively. These findings provide new quantitative tools for identifying flow regimes and improve the understanding and design of compact boiling-based thermal management systems under extreme heat- flux conditions. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

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