Fluid Mechanics, 2nd Edition

Topic Information

Dear Colleagues,

This topic is a continuation of the previous successful topic “Advances in Intelligent Construction, Operation and Maintenance” (https://www.mdpi.com/topics/fluid).

Fluid mechanics has been a topic of great practical and research interest for many centuries. Yet, this field of research is still young and vigorous, thanks to the tremendous opportunities that have been brought forward by modern computational and experimental techniques.

It is an amazingly wide and exciting area of knowledge, offering the possibility of applications in virtually every aspect of our lives. The present topical publication project offers the opportunity to communicate recent research results and application experiences across a wide range of sciences.

We are pleased to invite the research community to submit research or review articles on, but not limited to, the following relevant topics within the fluid mechanics space:

• Modern mathematical and computational methods for the investigation of fluid mechanics problems;
• Modern experimental techniques applicable to fluid mechanics;
• Instability and turbulence;
• Single- (fluid, gas) and multi-phase flows;
• Rheology;
• Lubrication;
• Magnetohydrodynamics;
• Plasma dynamics;
• Internal and external flows;
• Geophysical flows;
• Flows in industrial devices;
• Microfluid flows;
• Nanofluid flows;
• Filtration flows;
• Flows in biology and medicine;
• Flows of chemically reactive systems;
• Flows in aerospace applications;
• Compressible flows with shock waves and flows associated with explosions;
• Astrophysical flows.

Dr. Sihui Hong
Prof. Dr. Chaobin Dang
Prof. Dr. Shuangfeng Wang
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.5	2011	19.8 Days	CHF 2400	Submit
Energies energies	3.2	7.3	2008	16.2 Days	CHF 2600	Submit
Fluids fluids	1.8	4.0	2016	21.7 Days	CHF 1800	Submit
Materials materials	3.2	6.4	2008	15.2 Days	CHF 2600	Submit
Mathematics mathematics	2.2	4.6	2013	18.4 Days	CHF 2600	Submit
Micromachines micromachines	3.0	6.0	2010	17.2 Days	CHF 2100	Submit

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Published Papers (11 papers)

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All Applied Sciences Energies Fluids Materials Mathematics Micromachines

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21 pages, 3216 KB  

Open AccessArticle

Enhancement of Aerodynamic Performance of Two Adjacent H-Darrieus Turbines Using a Dual-Rotor Configuration

by Douha Boulla, Saïf ed-Dîn Fertahi, Maryam Bernatchou, Abderrahim Samaouali and Asmae Arbaoui

Fluids 2025, 10(9), 239; https://doi.org/10.3390/fluids10090239 - 8 Sep 2025

Viewed by 1035

Abstract

Improvements in the aerodynamic performance of the H-Darrieus turbine are crucial to address future energy requirements. This work aims to optimize the behavior of two adjacent turbines through the addition of a dual H-Darrieus rotor. The first rotor is composed of three NACA [...] Read more.

Improvements in the aerodynamic performance of the H-Darrieus turbine are crucial to address future energy requirements. This work aims to optimize the behavior of two adjacent turbines through the addition of a dual H-Darrieus rotor. The first rotor is composed of three NACA 0021 blades, while the second comprises a single Eppler 420 blade. This study focuses on 2D CFD simulation based on the solution of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations, using the sliding mesh method and $k-\omega$ SST turbulence model. The simulation results indicate a 17% improvement in the efficiency of the two turbines integrating dual rotors, compared to the two isolated turbines, for $\alpha$ = 0°. Moreover, the power coefficient ${ (C}_P)$ reaches maximum values of 0.49, 0.42, and 0.40 for angles of attack of 30°, 25°, and 20°, respectively, at TSR = 2.51. Conversely, the selection of an optimal angle of attack allows the efficiency of the two H-Darrieus turbines to be increased. It is also shown by the results that the effect of stagnation is reduced and lift is maximized when the optimum distance between two adjacent turbines is chosen. Moreover, the overall aerodynamic performance of the system is enhanced by the potential of a dual-rotor configuration, and the wake between the two turbines is disrupted, which can result in a decrease in energy production within wind farms. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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16 pages, 2639 KB  

Open AccessArticle

Analysis of the Evolution of Shock Waves When a Muzzle Jet Impacts a Constrained Moving Body

by Zijie Li and Hao Wang

Fluids 2025, 10(3), 57; https://doi.org/10.3390/fluids10030057 - 26 Feb 2025

Viewed by 595

Abstract

The evolution form of the flow field generated via the impact of a muzzle jet on a constrained moving body changes from the state of fully free-spatial development to that of constrained development, and it involves the problem of interference, owing to the [...] Read more.

The evolution form of the flow field generated via the impact of a muzzle jet on a constrained moving body changes from the state of fully free-spatial development to that of constrained development, and it involves the problem of interference, owing to the spatiotemporal coupling of various kinds of shock waves and vortices. Against this backdrop, the authors use the dynamic mesh method to establish two models for simulating the flow field and exploring the mechanism of development and the characteristics of propagation of disturbances induced via the shock waves as the muzzle jet impacts a constrained moving body. The results show that the muzzle jet exhibited a circumferentially asymmetric shape under the influence of the constrained track. The shock wave leaned towards the upper part of the muzzle, and its speed of propagation above the muzzle was higher than that below the muzzle. Meanwhile, the vortex that should have been present below the muzzle disappeared, and it was replaced with a separation line. Changes in the pressure of the flow field and important parameters of the moving body also became more complex due to the influence of the constrained track. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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27 pages, 7963 KB  

Open AccessReview

Research Progress and Engineering Applications of Viscous Fluid Mechanics

by Jianjun Peng, Run Feng, Meng Xue, Erhao Zhou, Junhua Wang, Zhidan Zhong and Xiangchen Ku

Appl. Sci. 2025, 15(1), 357; https://doi.org/10.3390/app15010357 - 2 Jan 2025

Cited by 2 | Viewed by 3293

Abstract

This paper systematically reviews the development of viscous fluid mechanics and expounds the current research status of viscous fluid mechanics from the aspects of permeability experiments and research on viscous fluids, particle distribution and movement, droplet impact, modern computer technology simulation, etc. This [...] Read more.

This paper systematically reviews the development of viscous fluid mechanics and expounds the current research status of viscous fluid mechanics from the aspects of permeability experiments and research on viscous fluids, particle distribution and movement, droplet impact, modern computer technology simulation, etc. This paper summarizes the application status of viscous fluid mechanics theory in aerospace, fluid simulation, bioengineering, pipeline transportation, and other engineering fields, analyzes the influence of multiphysical field coupling, complex flow, and new materials on viscous fluid mechanics, and puts forward its development trend in algorithms, simulation, biomedicine, aerospace, and other fields. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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23 pages, 7167 KB  

Open AccessArticle

Features of Structure and Flow Field in Homemade Co-Current Cavitation Water Jet Nozzle

by Chenhao Guo, Xing Dong, Haorong Song and Yun Jiang

Materials 2025, 18(1), 146; https://doi.org/10.3390/ma18010146 - 2 Jan 2025

Viewed by 990

Abstract

The cavitation water jet cleaning and coating removal technique represents an innovative sustainable method for cleaning and removing coatings, with the nozzle serving as a crucial component of this technology. Developing an artificially submerged nozzle with a reliable structure and excellent cavitation performance [...] Read more.

The cavitation water jet cleaning and coating removal technique represents an innovative sustainable method for cleaning and removing coatings, with the nozzle serving as a crucial component of this technology. Developing an artificially submerged nozzle with a reliable structure and excellent cavitation performance is essential for enhancing cavitation water jets’ cleaning and coating removal efficacy in an atmosphere environment (non-submerged state). This study is based on the shear flow cavitation mechanism of an angular nozzle, the resonance principle of an organ pipe, and the jet pump principle. A dual-nozzle co-current cavitation water jet nozzle structure was designed and manufactured. The impact of the nozzle’s inlet pressure on the vapor volume percentage, as well as the axial and radial velocities inside the flow field, were examined utilizing ANSYS Fluent software with the CFD method. The dynamic change rule of the cavitation cloud is derived by analyzing the picture of the cavitation cloud in the nozzle’s outflow field utilizing pseudo-color imaging techniques. The results show that the maximum vapor volume percentage is more significant than 95% for different inlet pressures in the internal nozzle. The changes that occur in the cavitation cloud exhibit notable regularity, including the four stages of cavitation, which are inception, development, shedding, and collapse. A change period is 1.5 ms, which proves that the homemade co-current cavitation water jet nozzle can achieve good cavitation effects. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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25 pages, 23481 KB  

Open AccessArticle

Effects of Pressure, Surfactant Concentration, and Heat Flux on Pool Boiling Using Expanding Microchanneled Surface for Two-Phase Immersion Cooling

by Yifei Hu, Dengwei Fu, Chaobin Dang and Sihui Hong

Materials 2024, 17(21), 5155; https://doi.org/10.3390/ma17215155 - 23 Oct 2024

Cited by 2 | Viewed by 1351

Abstract

Deionized water is replacing fluorinated liquids as the preferred choice for two-phase immersion cooling in data centers. Yet, insufficient bubble removal capability at low saturated pressure is a key challenge hindering the widespread application. To solve this issue, this study employs non-ionic surfactant [...] Read more.

Deionized water is replacing fluorinated liquids as the preferred choice for two-phase immersion cooling in data centers. Yet, insufficient bubble removal capability at low saturated pressure is a key challenge hindering the widespread application. To solve this issue, this study employs non-ionic surfactant (Tween 20) and asymmetric structures (expanding microchannel) to enhance the boiling performances of deionized water under sub-atmospheric pressure. The research examines the effects of pressure (8.8~38.5 kPa), surfactant concentration (0.1~0.5 mL/L), and heat flux density (10~180 W/cm²) on the boiling heat transfer characteristics and analyzes the mechanism of unusual temperature oscillations induced by surfactants. It was found that the trade-off between the sub-atmospheric pressure, surface tension coefficient, and reduced static contact angle results in pronounced intermittent boiling on the heated surface. Even with the addition of surfactants, the improvement in heat transfer requires demanding conditions. Boiling enhancement throughout all heat flux conditions was achieved when the surfactant concentration was higher than 0.2 mL/L for the expanding microchanneled surface. The heat transfer coefficient reached 6.89 W·cm⁻²·K⁻¹ under 8.8 kPa, which was 45% higher than without the surfactant. Under the same heat flux and sub-atmospheric pressure, as the concentration increased from 0.1 to 0.5 mL/L, the amplitudes of temperature fluctuation of the plane surface and expanding microchanneled surface decreased from 10 K to 2 K and 18 K to 1 K, respectively. The onset of nucleate boiling and wall superheat of the expanding microchanneled surface gradually decreased with the increase in surfactant concentration, where the onset of nucleate boiling decreased by 10.54 K. When the heat flux is 160 W/cm², the wall superheat is reduced by 12.8 K. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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16 pages, 6376 KB  

Open AccessArticle

Strength and Vibration Analysis of Axial Flow Compressor Blades Based on the CFD-CSD Coupling Method

by Haiwei Lin, Hong Bao, Huaihuai Zhang, Feifei Zhao and Junli Wang

Appl. Sci. 2024, 14(16), 7432; https://doi.org/10.3390/app14167432 - 22 Aug 2024

Cited by 1 | Viewed by 1889

Abstract

During the operational process of an axial-flow compressor, the blade structure is simultaneously subjected to both aerodynamic loads and centrifugal loads, posing significant challenges to the safe and reliable operation of the blades. Considering both centrifugal loads and aerodynamic loads comprehensively, a bidirectional [...] Read more.

During the operational process of an axial-flow compressor, the blade structure is simultaneously subjected to both aerodynamic loads and centrifugal loads, posing significant challenges to the safe and reliable operation of the blades. Considering both centrifugal loads and aerodynamic loads comprehensively, a bidirectional CFD-CSD coupling analysis method for blade structure was established. The Navier–Stokes governing equations were utilized to solve the internal flow field of the axial-flow compressor. The conservative interpolation method was utilized to couple and solve the blade’s static equilibrium equation, and the deformation, stress distribution, and prestress modal behavior of compressor blades were mainly analyzed. The research results indicate that the maximum deformation of the blades occurred at the lead edge tip, while stress predominantly concentrated approximately 33% upward from the blade root, exhibiting a radial distribution that gradually decreased. As the rotational speed increased, the maximum deformation of the blades continuously increased. Furthermore, at a constant rotational speed, the maximum deformation of the blade exhibited a trend of first increasing and then decreasing with the increase in mass flow. In contrast, the maximum stress showed a trend of first increasing, then decreasing, and finally increasing again as the rotational speed continuously increased. Centrifugal loads are the primary factor influencing blade stress and natural frequency. During operation, the blades exhibited two resonance points, approximately occurring at 62% and 98% of the design rotational speed. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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15 pages, 3398 KB  

Open AccessArticle

Analyzing the Biomechanical Characteristics of Ski Jumping Take-Off Phase Based on CFD

by Bojie Hou, Zhongqiu Ji, Yun Zhang and Mingyan Yu

Appl. Sci. 2024, 14(16), 7203; https://doi.org/10.3390/app14167203 - 16 Aug 2024

Cited by 1 | Viewed by 1521

Abstract

This study aimed to analyze the aerodynamic characteristics of Chinese Nordic combined athletes during the ski jump take-off process, comparing them with elite athletes from the 2009 Nordic World Ski Championships using computational fluid dynamics (CFD) methods. Methods: Using 3D model analysis and [...] Read more.

This study aimed to analyze the aerodynamic characteristics of Chinese Nordic combined athletes during the ski jump take-off process, comparing them with elite athletes from the 2009 Nordic World Ski Championships using computational fluid dynamics (CFD) methods. Methods: Using 3D model analysis and continuous relative phase analysis, CFD methods were utilized to assess the mechanical characteristics of athletes during the take-off phase. Results: The analysis revealed that Chinese athletes displayed a lower dominance of the knee joint during the take-off phase, leading to increased air drag. Conclusion: Reduced knee joint dominance and an excessive ankle angle at the initiation of the ski jump take-off contribute to higher air drag. The lean angle of the body and the ankle angle post-take-off significantly affect the resultant lift and drag forces. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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19 pages, 8201 KB  

Open AccessArticle

Propagation Mechanism of Pressure Waves during Pulse Hydraulic Fracturing in Horizontal Wells

by Yao Zhang, Jiye Zuo, Xinyu Fei and Shimin Dong

Appl. Sci. 2024, 14(16), 6982; https://doi.org/10.3390/app14166982 - 9 Aug 2024

Viewed by 1790

Abstract

Hydraulic fracturing, especially pulse hydraulic fracturing, is an important method for extracting oil and gas from low-permeability reservoirs, improving recovery rates significantly. Pulse hydraulic fracturing, which involves varying injection rates to create pressure waves, outperforms traditional constant-flow fracturing methods significantly. However, during pulse [...] Read more.

Hydraulic fracturing, especially pulse hydraulic fracturing, is an important method for extracting oil and gas from low-permeability reservoirs, improving recovery rates significantly. Pulse hydraulic fracturing, which involves varying injection rates to create pressure waves, outperforms traditional constant-flow fracturing methods significantly. However, during pulse hydraulic fracturing operations, the flow properties of the fluid in the column change from moment to moment. Furthermore, current research on pulse hydraulic fracturing primarily focuses on vertical wells, while horizontal wells have become a common operational strategy. Therefore, a transient flow model of fluid within a horizontal well, considering variable-flow injection and unsteady friction conditions, is established in this paper. The model is solved using both the characteristic line method and the finite difference method. The hydrodynamic properties of the fracturing fluid were analyzed, and the propagation mechanisms of pressure waves within horizontal wells under various fluid injection schemes and well depths are analyzed to provide a reference for selecting appropriate fluid injection schemes in engineering practice. The study highlights the impact of fluid viscosity and injection flow amplitude on bottomhole pressure fluctuations, advancing the efficient development of low-permeability oilfields. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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23 pages, 1999 KB  

Open AccessArticle

Numerical Solution of the Newtonian Plane Couette Flow with Linear Dynamic Wall Slip

by Muner M. Abou Hasan, Ethar A. A. Ahmed, Ahmed F. Ghaleb, Moustafa S. Abou-Dina and Georgios C. Georgiou

Fluids 2024, 9(8), 172; https://doi.org/10.3390/fluids9080172 - 27 Jul 2024

Cited by 2 | Viewed by 1769

Abstract

An efficient numerical approach based on weighted-average finite differences is used to solve the Newtonian plane Couette flow with wall slip, obeying a dynamic slip law that generalizes the Navier slip law with the inclusion of a relaxation term. Slip is exhibited only [...] Read more.

An efficient numerical approach based on weighted-average finite differences is used to solve the Newtonian plane Couette flow with wall slip, obeying a dynamic slip law that generalizes the Navier slip law with the inclusion of a relaxation term. Slip is exhibited only along the fixed lower plate, and the motion is triggered by the motion of the upper plate. Three different cases are considered for the motion of the moving plate, i.e., constant speed, oscillating speed, and a single-period sinusoidal speed. The velocity and the volumetric flow rate are calculated in all cases and comparisons are made with the results of other methods and available results in the literature. The numerical outcomes confirm the damping with time and the lagging effects arising from the Navier and dynamic wall slip conditions and demonstrate the hysteretic behavior of the slip velocity in following the harmonic boundary motion. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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14 pages, 10050 KB  

Open AccessArticle

Study on the Tribological Properties of Multilayer Concentric Hexagonal Laser Texturing on Rubber Surfaces of Screw Pumps

by Xinfu Liu, Xinglong Niu, Chunhua Liu, Xiangzhi Shi, Yi Sun, Zhongxian Hao, Shouzhi Huang, Yuan Wang and Hua Tao

Materials 2024, 17(15), 3708; https://doi.org/10.3390/ma17153708 - 26 Jul 2024

Cited by 5 | Viewed by 1246

Abstract

Given the friction and drag reduction effects observed in various biological hexagonal structures in nature, a new design was implemented on the rubber surface of the stator of a submersible screw pump. This design featured a multilayer concentric hexagonal groove structure. Furthermore, a [...] Read more.

Given the friction and drag reduction effects observed in various biological hexagonal structures in nature, a new design was implemented on the rubber surface of the stator of a submersible screw pump. This design featured a multilayer concentric hexagonal groove structure. Furthermore, a composite multilayer hexagonal structure integrating grooves and pits was also developed and applied. This study investigated the influence of groove layer number, groove depth, pit depth, and multilayer hexagonal groove texture arrangement on the rubber surface flow characteristics. Additionally, the pressure field state, the degree of influence on the oil film-bearing capacity, and the biomimetic and hydrodynamic lubrication theories were tested using the finite element analysis method. Tribological experiments were conducted on nanosecond laser-processed rubber textures under simulated liquid lubrication conditions, reflecting actual shale oil well experiments. These experiments aimed to investigate the influence of multilayer hexagonal shape parameters on the tribological characteristics of the stator-rotor friction pair of a submersible screw pump. The results indicated that with a constant overall size, a multilayer hexagonal structure with ~0.1 mm groove depth enhanced the oil film-bearing capacity, providing significant friction and drag reduction. For composite textures, a deeper pit depth within the study area enhanced the oil film-bearing capacity. Furthermore, a gradient arrangement of groove textures featuring wider outer grooves and shallower depth exhibited superior performance in terms of bearing capacity. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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15 pages, 842 KB  

Open AccessArticle

A Physical Insight into Computational Fluid Dynamics and Heat Transfer

by Sergey I. Martynenko and Aleksey Yu. Varaksin

Mathematics 2024, 12(13), 2122; https://doi.org/10.3390/math12132122 - 6 Jul 2024

Cited by 4 | Viewed by 1287

Abstract

Mathematical equations that describe all physical processes are valid only under certain assumptions. One of them is the minimum scales used for the given description. In fact, this prohibits the use of derivatives in the mathematical models of the physical processes. This article [...] Read more.

Mathematical equations that describe all physical processes are valid only under certain assumptions. One of them is the minimum scales used for the given description. In fact, this prohibits the use of derivatives in the mathematical models of the physical processes. This article represents a derivative-free approach for the mathematical modelling. The proposed approach for CFD and numerical heat transfer is based on the conservation and phenomenological laws, and physical constraints on the minimum problem-dependent spatial and temporal scales (for example, on the average free path of molecules and the average time of their collisions for gases). This leads to the derivative-free governing equations (the discontinuum approximation) that are very convenient for numerical simulation. The theoretical analysis of governing equations describing the fundamental conservation laws in the continuum and discontinuum approximations is given. The article demonstrates the derivative-free approach based on the correctly defined macroparameters (pressure, temperature, density, etc.) for the mathematical description of physical and chemical processes. This eliminates the finite-difference, finite-volume, finite-element or other approximations of the governing equations from the computational algorithms. Full article

(This article belongs to the Topic Fluid Mechanics, 2nd Edition)

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