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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 (31 January 2025) | Viewed by 15564

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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
Special Issues, Collections and Topics in MDPI journals

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; unteady flow; hydraulic design
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Dr. Yongyao Luo

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Guest Editor

Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
Interests: hydrodynamics simulation; pump-turbine; tidal energy; multi-phase flow
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Dr. Wenwu Zhang

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Guest Editor

College of Water Resources and Civil Engineering, China Agricutural University, Beijing 100191, China
Interests: pumps; gas-liquid two-phase flow; unteady flow; hydraulic design
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 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 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. Yongyao Luo
Dr. Wenwu Zhang
Guest Editors

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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.

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Keywords

hydrodynamic experiment
hydrodynamic simulation
hydraulic machinery
multiphase flow
hydro-energy technology

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Published Papers (13 papers)

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Research

15 pages, 10318 KiB

Open AccessArticle

Study on the Complex Erosion Characteristics and Specific Influencing Factor Mechanism in a Francis Hydraulic Turbine

by Jinliang Wang, Xijie Song, Jiabing Wang and Zhengwei Wang

Water 2025, 17(8), 1234; https://doi.org/10.3390/w17081234 - 21 Apr 2025

Viewed by 260

Abstract

Sediment erosion of hydraulic turbines has gradually become a key factor affecting their long-term stable operation. There are many different factors that can cause erosion in the Francis hydraulic turbine; among them, the vortex occurs in the turbine, which is also a negative factor for the unit. In this paper, the purpose is to study the complex erosion characteristics and specific influencing factor mechanism. The method is based on numerical simulation, combined with the verification data on site. Research results show that the differences in flow patterns among various components correspond to the erosion distribution of the unit at the same location, indicating that local flow patterns affect the unit’s erosion. The highest total erosion rate is on the surface of the runner at 1.08 × 10⁻³ kg·s⁻¹·m⁻². The erosion rate on the guide vane wall is second highest, also at 9.8 × 10⁻⁴ kg·s⁻¹·m⁻². The total erosion rate in the clearance is lower than that on the guide vane wall at 7.03 × 10⁻⁴ kg·s⁻¹·m⁻². The lowest total erosion rate is found in the draft tube at 2.57 × 10⁻⁴ kg·s⁻¹·m⁻². The effect of local vortices not only exacerbate the microscopic damage on the blade surface but also leads to a more obvious nonuniform erosion distribution, especially at the clearance, where erosion is more severe. The vortex in the guide vane passage alters the particle trajectory at the guide vane outlet, increasing the erosion in the guide vane clearance. Similarly, the vortex in the draft tube increases particle rotation, enhancing erosion on the draft tube wall. Research indicates that eliminating vortices is beneficial for reducing sediment erosion within the unit. The research results provide a theoretical basis for the optimization design of Francis hydraulic turbine. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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20 pages, 7893 KiB

Open AccessArticle

Simulation of Control Process of Fluid Boundary Layer on Deposition of Travertine Particles in Huanglong Landscape Water Based on Computational Fluid Dynamics Software (CFD)

by Xinze Liu, Wenhao Gao, Yang Zuo, Dong Sun, Weizhen Zhang, Zhipeng Zhang, Shupu Liu, Jianxing Dong, Shikuan Wang, Hao Xu, Hongwei Chen and Mengyu Xu

Water 2025, 17(5), 638; https://doi.org/10.3390/w17050638 - 22 Feb 2025

Viewed by 508

Abstract

This research explores the distribution, transport, and deposition of calcium carbonate particles in the colorful pools of the Huanglong area under varying hydrodynamic conditions. The study employs Particle Image Velocimetry (PIV) for real-time measurements of flow field velocity and computational fluid dynamics (CFD) simulations to analyze particle behavior. The findings reveal that under horizontal flow conditions, the peak concentration of calcium carbonate escalated to 1.06%, representing a 6% surge compared to the inlet concentration. Significantly, particle aggregation and settling were predominantly noted at the bottom right of the flow channel, where the flow boundary layer is most pronounced. In the context of inclined surfaces equipped with a baffle, a substantial rise in calcium carbonate concentrations was detected at the channel’s bottom right and behind the baffle, particularly in regions characterized by reduced flow velocities. These low-velocity areas, along with the interaction of the boundary layer and low-speed vortices, led to a decrease in particle velocities, thereby enhancing deposition. The highest concentrations of calcium carbonate particles were found in regions characterized by thicker boundary layers, particularly in locations before and after the baffle. Using the Discrete Phase Model (DPM 22), the study tracked the trajectories of 2424 particles, of which 2415 exited the computational channel and nine underwent deposition. The overall deposition rate was measured at 0.371%, with calcium carbonate deposition rates ranging from 4.06 mm/a to 81.7 mm/a, closely matching field observations. These findings provide valuable insights into the dynamics of particle transport in aquatic environments and elucidate the factors influencing sedimentation processes. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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18 pages, 20156 KiB

Open AccessArticle

Study on Sand Wear Testing and Numerical Simulation of a 500 MW Class Pelton Turbine

by Jialing Li, Jiayang Pang, Mengjun Qin, Xiaobing Liu, Hong Hua, Baofu Wu, Haiku Zhang, Jitao Liu, Zhishun Yu and Yongzhong Zeng

Water 2025, 17(3), 317; https://doi.org/10.3390/w17030317 - 23 Jan 2025

Viewed by 772

Abstract

Pelton turbines frequently encounter significant sediment wear when operating in sandy river environments. The runner bucket of these turbines is particularly prone to wear, which results in considerable reductions in turbine efficiency and operational stability. This research focused on a large-scale Pelton turbine with a 500 MW standalone capacity in a sandy river setting. Numerical simulations of sand–water flow within the runner bucket were conducted using the volume of fluid (VOF) model, shear stress transport (SST) k-ω model, and the discrete phase model (DPM). Additionally, a sediment wear prediction model, based on wear tests conducted on a model turbine, was utilized to estimate sediment wear within the Pelton turbine bucket. The results indicated a maximum bucket wear rate of 2.61 × 10⁻⁷ mm/s. Specifically, the 04Cr13Ni5Mo runner bucket, typically made from stainless-steel wear-resistant material, is expected to experience over 5.62 mm of wear after one year of operation under rated conditions, emphasizing the severity of sediment wear. To prolong the operational life of the unit, further investigations into surface wear resistance treatments for the runner water buckets are recommended. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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22 pages, 9154 KiB

Open AccessArticle

Turbulent Flow Through Sluice Gate and Weir Using Smoothed Particle Hydrodynamics: Evaluation of Turbulence Models, Boundary Conditions, and 3D Effects

by Efstathios Chatzoglou and Antonios Liakopoulos

Water 2025, 17(2), 152; https://doi.org/10.3390/w17020152 - 8 Jan 2025

Viewed by 1045

Abstract

Understanding flow dynamics around hydraulic structures is essential for optimizing water management systems and predicting flow behavior in real-world applications. In this study, we simulate a 3D flow control system featuring a sluice gate and a weir, commonly used in hydraulic engineering. The focus is on accurately incorporating modified dynamic boundary conditions (mDBCs) and viscosity treatment to improve the simulation of complex, turbulent flows. We assess the performance of the Smoothed Particle Hydrodynamics (SPH) method in handling these challenging conditions. Especially when the boundary conditions and applicability to industry are two of the SPH method’s grand challenges. Simulations were conducted on a Graphics Processing Unit (GPU) using the DualSPHysics code. The results were compared to theoretical predictions and experimental data found in the literature. Key hydraulic characteristics, including 3D flow effects, hydraulic jump formation, and turbulent behavior, are examined. The combination of mDBCs with the Laminar plus sub-particle scale turbulence model achieved the correct simulation results. The findings demonstrate agreement between simulations, theoretical predictions, and experimental results. This work provides a reliable framework for analyzing turbulent flows in hydraulic structures and can be used as reference data or a prototype for larger-scale simulations in both research and engineering design, particularly in contexts requiring robust and precise flow control and/or environmental management. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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15 pages, 6607 KiB

Open AccessArticle

A Comparative Analysis on the Vibrational Behavior of Two Low-Head Francis Turbine Units with Similar Design

by Weiqiang Zhao, Jianhua Deng, Zhiqiang Jin, Ming Xia, Gang Wang and Zhengwei Wang

Water 2025, 17(1), 113; https://doi.org/10.3390/w17010113 - 3 Jan 2025

Cited by 3 | Viewed by 937

Abstract

With the requirement of flexible operation of hydraulic turbine units, Francis turbine units have to adjust their output into extended operating ranges in order to match the demand of the power grid, which leads to more off-design conditions. In off-design conditions, hydraulic excitation causes excessive stress, pressure pulsation, and vibration on the machines. Different designs of Francis turbines cause different hydraulic excitations and vibrational behaviors. To conduct better condition monitoring and fault prognosis, it is of paramount importance to understand the vibrational behavior of a machine. In order to reveal the influence factors of the vibration behavior of Francie turbine units, field tests have been conducted on two similar-designed Francis turbine units and vibration features have been compared in this research. The vibrational behavior of two Francis turbine units installed in the same power station is compared under extended operating condition. Field tests have been performed on the two researched units and the vibration has been compared using the spectrum analysis method. The vibration indicators are extracted from the test data and the variation rules have been compared. By comparing the vibration behavior of the two machines, the design and installation difference of the two machines have been analyzed. This research reveals the effects of different designs and installations of Francis turbines on the vibration performance of the prototype units. The obtained results give guidance to the designers and operators of Francis turbine units. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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16 pages, 6249 KiB

Open AccessArticle

Impact of the Draft Plate on the Wall Erosion and Flow Field Stability of a Cyclone Separator

by Yida Zhang, Xiaodong Zhang and Yanjiao Gao

Water 2024, 16(21), 3142; https://doi.org/10.3390/w16213142 - 3 Nov 2024

Cited by 2 | Viewed by 1228

Abstract

Cyclone separators are commonly employed in the mining, metallurgy and chemical industries due to their simple structure, easy maintenance and high recovery efficiency. However, with the wide application of cyclone separators, many problems have become exposed in their practical operation, restricting their development. Among these, wall erosion is becoming a significant problem. In this study, to resolve the problem of severe erosion on the walls, the Eulerian–Lagrangian framework was employed to investigate a cyclone separator with a draft plate at the inlet and to evaluate the effect of a draft plate with angles of 0°, 45° and 90° on the degree of erosion and the stabilization of flow fields. Moreover, after verifying the reliability of the numerical model via data from experiments, the characteristics of gas–solid flow were analyzed and the effects of the new structure on the degree of wear were investigated. The results demonstrated that unfavorable phenomena such as secondary flow and wall erosion generated during the operation could be mitigated by the draft plate. When the plate angle was 90°, the wall erosion was the lightest and the range of influence of the secondary flow was the smallest. When the plate angle was 45°, the comprehensive performance was the best, and there was a better balance between the energy loss and the degree of wall erosion. Therefore, the presence of the draft plate has a significant impact on the interaction of gas–solid phases in a cyclone separator. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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19 pages, 9672 KiB

Open AccessArticle

Analysis of Unsteady Flow and Interstage Interference of Pressure Pulsation of Two-Stage Pump as Turbine Under Turbine Model

by Yonggang Lu, Zhiwang Liu, Zequan Zhang, Weike Liao, Xiaolong Li and Alexandre Presas

Water 2024, 16(21), 3100; https://doi.org/10.3390/w16213100 - 29 Oct 2024

Viewed by 1194

Abstract

The process pump as turbine (PPAT) serves as a crucial component for recovering high-pressure energy from mediums used in chemical and refining processes. Ensuring the long-term safe and stable operation of PPAT in high-temperature and high-pressure environments is essential, with pressure pulsation being one of its most significant external characteristic indicators. This study investigates the evolution of vortex structure distribution and the generation and propagation mechanisms of pressure pulsation in a two-stage PPAT operating in turbine mode. Results indicate that the uniformity of the pressure coefficient (Cp) gradient distribution is poorer in the first stage runner compared to the second stage, with a larger distribution area of high-strength vortices. In the draft tube, vortex strength increases with rising flow rates, and the flow around the circular cylinder on one side gradually develops to both sides. In the two-stage diffusers, the primary source of pressure pulsation is the dynamic and static interference effect between the two impellers and the corresponding diffuser tongue. The interstage interference with a frequency of n*15fn is most pronounced in the inflow runner, gradually weakening along the flow direction, and ultimately disappearing in the draft tube. In addition, more low-frequency signals with a frequency of 0.5fn are captured in the draft tube under large flow conditions, which is mainly generated by the vortex band in the draft tube. The low-frequency pulsation energy is high and the attenuation is slow, which has a great destructive effect on the energy recovery system of the PPAT. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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28 pages, 16454 KiB

Open AccessArticle

Investigation and Improvement of Centrifugal Slurry Pump Wear Characteristics via CFD-DEM Coupling

by Zengqiang Wang, Guangjie Peng, Hao Chang, Shiming Hong and Guangchao Ji

Water 2024, 16(21), 3050; https://doi.org/10.3390/w16213050 - 24 Oct 2024

Cited by 1 | Viewed by 1266

Abstract

Centrifugal slurry pumps are extensively applied in industrial industries such as power metallurgy, petrochemicals, deep-sea mining, and other industrial fields. The primary objective of this research is to assess how conveying settings and particle characteristics influence the 100SHL4147 slurry pump’s collision and erosion properties. Firstly, the computational fluid dynamics–discrete element method (CFD-DEM) coupling model fully coupled particle–fluid co-flow numerical simulation interface is built by utilizing the C++ language and the results are proven with tests. Subsequently, the simulation examines the wear properties of different sections through which the flow passes in the 100SHL4147 centrifugal slurry pump. In addition, following theoretical guidance, the slurry pump impeller’s wear resistance performance can be improved by adjusting design factors such as the intake edge location and the blade wrap angle. The results are as follows. It is recommended to replace the impeller promptly due to the findings that indicate that the entire blade’s pressure surface is vulnerable to different degrees of erosion under high-concentration situations. When the particle size increased from 0.4 to 0.8 mm, the wear rate decreased by up to 15%, as fewer particles were transported, lowering the collision frequency. Conversely, smaller particles intensify component wear. Adjusting the blade wrap angle from 66° to 96° reduced impeller and volute wear by an estimated 20%, enhancing the durability but slightly decreasing the delivery capacity. Extending the blade’s leading edge toward the intake improved the flow capacity, although it increased the wear frequency from one-third of the pressure surface to the trailing edge. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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28 pages, 9980 KiB

Open AccessArticle

Research on the Influence of Particles and Blade Tip Clearance on the Wear Characteristics of a Submersible Sewage Pump

by Guangjie Peng, Jinhua Yang, Lie Ma, Zengqiang Wang, Hao Chang, Shiming Hong, Guangchao Ji and Yuan Lou

Water 2024, 16(19), 2845; https://doi.org/10.3390/w16192845 - 7 Oct 2024

Cited by 1 | Viewed by 1285

Abstract

A submersible sewage pump is designed for conveying solid–liquid two-phase media containing sewage, waste, and fiber components, through its small and compact design and its excellent anti-winding and anti-clogging capabilities. In this paper, the computational fluid dynamics–discrete element method (CFD-DEM) coupling model is used to study the influence of different conveying conditions and particle parameters on the wear of the flow components in a submersible sewage pump. At the same time, the energy balance equation is used to explore the influence mechanism of different tip clearance sizes on the internal flow pattern, wear, and energy conversion mechanism of the pump. This study demonstrates that increasing the particle volume fraction decreases the inlet particle velocity and intensifies wear in critical areas. When enlarging the tip clearance thickness from 0.4 mm to 1.0 mm, the leakage vortex formation at the inlet is enhanced, leading to increased wear rates in terms of the blade and volute. Consequently, the total energy loss and turbulent kinetic energy generation increased by 3.57% and 2.25%, respectively, while the local loss coefficient in regard to the impeller channel cross-section increased significantly. The findings in this study offer essential knowledge for enhancing the performance and ensuring the stable operation of pumps under solid–liquid two-phase flow conditions. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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19 pages, 11946 KiB

Open AccessArticle

Study on Transient Flow Characteristics of Pump Turbines during No-Load Condition in Turbine Mode Startup

by Xianliang Li, Haiyang Dong, Yonggang Lu, Xiji Li and Zhengwei Wang

Water 2024, 16(19), 2741; https://doi.org/10.3390/w16192741 - 26 Sep 2024

Viewed by 852

Abstract

To address the escalating demand for power grid load regulation, pumped storage power stations must frequently switch between operational modes. As a key component of such stations, the pump turbine has seen extensive research on its steady-state flow behavior. However, the intricate dynamics of its transient flow have not yet been thoroughly examined. Notably, the no-load condition represents a quintessential transient state, the instability of which poses challenges for grid integration. Under certain extreme conditions, this could result in the impairment of the unit’s elements, interruption of its functioning, and endangerment of the security of the power station’s output as well as the stability of the power network’s operations. Thus, investigating the flow characteristics of pump turbines under no-load conditions is of significant practical importance. This paper focuses on the transient flow characteristics of a Weifang hydro-generator unit under no-load conditions, exploring the internal unsteady flow features and their underlying mechanisms. The study reveals that under no-load conditions, the runner channel is obstructed by a multitude of vortices, disrupting the normal pressure gradient within the runner and resulting in substantial hydraulic losses. Within the draft tube, a substantial reverse flow zone is present, predominantly along the walls. This irregular flow pattern within the tube generates a potent, stochastic pressure fluctuation. In addition to the interference frequencies of dynamic and static origins, the pressure pulsation frequency at each measurement point also encompasses a substantial portion of low-frequency, high-amplitude components. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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16 pages, 7055 KiB

Open AccessArticle

Stability Study and Strengthening Strategy of Spiral Case-Encased Concrete Structure of Pumped Storage Power Station

by Yun Zhao, Xiji Li, Yonggang Lu, Haiyang Dong, Chuanzhen Sun and Zhengwei Wang

Water 2024, 16(18), 2687; https://doi.org/10.3390/w16182687 - 21 Sep 2024

Viewed by 1048

Abstract

With the development of global hydropower, the scale of hydropower stations is increasing, and the operating conditions are becoming more complex, so the stable operation of hydropower stations is very important. The vibration of the turbine unit will cause resonance in the powerhouse, and the structural stability of the powerhouse will be affected. Many scholars pay attention to the stability of the turbine unit operation, and there are few studies on the powerhouse of the hydropower station. Therefore, this paper relies on the Weifang Hydropower Station project to study key issues such as the tensile strength of concrete and how to arrange steel bars to increase the structural stability by changing the material properties through FEA. Three schemes are designed to evaluate the safety of the powerhouse structure when the turbine unit is running through the safety factor. Our findings indicate that the stress variation patterns observed on the inner surface of the powerhouse remain consistent across different operating scenarios. Notably, along the spiral line of the worm section, we observed that the stress levels on the vertical loop line decrease gradually with increasing distance from the inlet. Conversely, stress concentrations arise near the inlet and the tongue. Additionally, it has been noted that the likelihood of concrete cracking increases significantly at the tongue region. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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21 pages, 13626 KiB

Open AccessArticle

Numerical Simulation Study of Factors Influencing Ultrasonic Cavitation Bubble Evolution on Rock Surfaces during Ultrasonic-Assisted Rock Breaking

by Jinyu Feng, Tie Yan and Zhaokai Hou

Water 2024, 16(16), 2234; https://doi.org/10.3390/w16162234 - 8 Aug 2024

Cited by 6 | Viewed by 1910

Abstract

With the increasing demand for deep oil and gas exploration and CCUS (Carbon Capture, Utilization, and Storage) engineering, improving rock-crushing efficiency stands as a pivotal technology. Ultrasonic vibration-assisted drilling has emerged as a novel rock-breaking technology. The high-frequency vibrations of ultrasonic waves impact rocks, inducing resonance and accelerating their fragmentation. At the same time, ultrasonic waves generate cavitation bubbles in the liquid near rock surfaces; the expansion and collapse of these bubbles further contribute to rock damage, thereby improving crushing efficiency. Therefore, investigating the dynamics and failure characteristics of cavitation bubbles near rock surfaces under ultrasonic influence is crucial for advancing ultrasonic-assisted rock-breaking technology. This study treats the liquid as compressible flow and investigates the movement and rupture of bubbles near rock surfaces under varying ultrasonic parameters, rock properties, characteristics of the circulating medium, and other relevant factors. The findings show that ultrasonic waves induce the oscillation, translation, collapse, and rebound of bubbles near rock surfaces. Higher ultrasonic frequencies correspond to larger collapse pressures and amplitudes near surrounding rocks, as well as longer expansion times and shorter collapse durations. In addition, bubble movement and collapse lead to rock material deformation, influenced by the rheological properties of the liquid medium. The study outcomes serve as a foundation for optimizing engineering parameters in ultrasonic-assisted rock breaking and provide theoretical support for the advancement of this technology. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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17 pages, 69768 KiB

Open AccessArticle

Dynamic Response Characteristics of Rotating and Fixed Components of the Kaplan Turbine under Low and Medium Heads

by Hongyun Luo, Guiyu Wang, Xiaobin Chen, Chengming Liu, Lingjiu Zhou and Zhengwei Wang

Water 2024, 16(15), 2137; https://doi.org/10.3390/w16152137 - 28 Jul 2024

Viewed by 2183

Abstract

The vibration of large Kaplan turbines has always been one of the key research issues of turbines. Affected by the load and head of the power station, the Kaplan turbine will operate under medium and low heads, and the components will vibrate violently, seriously threatening the stable operation of the unit. Compared with other types of turbines, the runner structure of the Kaplan turbine is more complex. Therefore, in addition to the fixed components, the dynamic response characteristics of the rotating components are also be the focus of this study. In this paper, four operating points under high, medium and low heads are selected. The unsteady flow field and fluid–structure interaction are calculated. The modal and dynamic stress characteristics of the fixed components (bottom ring, head cover and support cover) and the rotating components (blades, runner body and main shaft) are analyzed. The results show that the location of the stress concentration of fixed components under low heads changes significantly, and the stress fluctuates greatly due to the influence of the stay vanes. The rotating components are more affected by the rotation of the runner under low heads, and the displacement and stress fluctuations of the rotating structure are significantly greater than those of medium and high heads. The pressure fluctuations in the vaneless area and draft tube cause some low-frequency excitation. The stress fluctuations of rotating components under low heads are much greater than those of the fixed components. This shows that the head has a greater impact on the rotating components, which is more likely to cause damage to the rotating components, seriously threatening the stable operation of the unit. Full article

(This article belongs to the Special Issue Hydrodynamic Science Experiments and Simulations)

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