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Liquid–Fluid Interfaces and Dynamics
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Liquid–Fluid Interfaces and Dynamics

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Liquid–Fluid Coatings, Surfaces and Interfaces".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 21465

Special Issue Editors

Dr. Liping Wei

E-Mail Website
Guest Editor
Xi'an Key Laboratory of Special Energy Materials, School of Chemical Engineering, International Scientific and Technological Cooperation Base for Clean Utilization of Hydrocarbon Resources, Northwest University, Xi'an 60208, China
Interests: multiphase flow and corrosion; CFD; coating and surface modification; energy technology
Special Issues, Collections and Topics in MDPI journals
Dr. Shunli Zheng

E-Mail Website
Guest Editor
College & Hospital of Stomatology, Anhui Medical University, Hefei 230032, China
Interests: protective (self-cleaning, self-healing, anti-corrosion, wear resistant, ice-phobic, etc.) coatings; epoxy coatings; anti-biofouling and anti-bacteria materials; surface modification; surface treatment and interface analyses
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Guirong Yang

E-Mail Website
Guest Editor
School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China
Interests: wear-resistant and corrosion-resistant functional coating on surfaces; composite melting layer with 3D network texture; corrosion behavior in gas–liquid two-phase flow; failure analysis of parts

Special Issue Information

Dear Colleagues,

In the oil and natural gas industry, the energy and power industry, the chemical and pharmaceutical industry, and the medical and healthcare indstry, the varaible fluids of liquid, gas, gas–liquid, and liquid–liquid mixture interact with the walls of pipes, vessels, and reactors during their transport, reaction, and mixing. Material corrosion is inevitable under the complex multiphase flow. To maintain the structural material integrity and reliability of assets under harsh environments of complex fluids, there is a demand to better understand the basic interaction mechanism of phase interface and corrosion and to develop new coatings and protection technologies. More experimental, theoretical, and modeling activities should be further focused on in this area.

With the development of renewable energy, energy storage, CCUS, and new medical technology, the demand for multiphase flow control and corrosion protection technology is increasingly strong. In addition, the booming measurement and characterization techniques, simualtion methods, and artificial intelligence technology provide scientists and engineers with more powerful investigation tools to better understand the basic mechanisms and develop coatings and protection strategies. The purpose of this Special Issue is to report the notable investigations of scientists and engineers in the areas of multiphase flow, multiphase interaction, material corrosion mechanisms in fluids, surface modifiacation, and coatings. 

The scope of this Special Issue will cover, but will not be limited to, the following contents:

  • Multiphase inteface behaviors (gas–liquid flow and interaction, liquid–liquid flow and interaction, multiphase transport);
  • Multiphase flow and wall interactions (mass trasnfer throguh the interface, collision, transport, erosion);
  • Material corrsion behavior within static and dyamics fluids (supercritical fluids, oil, water, syngas, natrual gas, amine solution, ionic liquid, phase changed liquid, electrolyte solution, etc.);
  • Recent developments in protective coatings and epoxy coatings for hydrophobic, superhydrophobic, self-cleaning, self-healing, anti-corrosion, ice-phobic, wear resistant, anti-biofouling, and anti-bacterial applications;
  • Surface modification produced by different processes (e.g., electrochemical, anodization and electroplating, etching, spraying, dipping, sol-gel, laser, and plasma techniques)
  • Phase-change processes of materials (e.g., organic phase-change material, inorganic phase-change material, composite phase-change material);
  • Theoretical calculation of a surface or interface (e.g., catalysis, corrosion behavior, wetting behavior, etc.)
  • Phase-interface behavior of energy materials (e.g., lithium-ion battery materials, sodium-ion battery material, explosive energetic material, etc.).

Dr. Liping Wei
Dr. Shunli Zheng
Prof. Dr. Guirong Yang
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 100 words) can be sent to the Editorial Office for announcement on this website.

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. Coatings 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 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

  • multiphase flow
  • corrsion behavior
  • functional coating
  • surface mofication
  • industrial
  • medical

Published Papers (15 papers)

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Research

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19 pages, 7133 KiB  
Article
Effect of the Injection Structure on Gas Velocity Distribution in a 3D Vertical Oven
by Qiucheng Zhou, Zhanyu Yang, Changsong Zheng, Liping Wei, Dong Li and Xiaoyong Fan
Coatings 2023, 13(10), 1707; https://doi.org/10.3390/coatings13101707 - 28 Sep 2023
Viewed by 657
Abstract
Gas injection structures were designed for a vertical oven to improve the gas–solid flow countercurrent structure. This work measured the wall temperature distribution of the vertical oven to reflect gas velocity distribution, and simulated the basic gas–solid flow field. The effects of the [...] Read more.
Gas injection structures were designed for a vertical oven to improve the gas–solid flow countercurrent structure. This work measured the wall temperature distribution of the vertical oven to reflect gas velocity distribution, and simulated the basic gas–solid flow field. The effects of the number of gas orifice layers and the injection angle on the gas velocity distribution were examined. The results showed that number of gas injection layers had a significant effect on the gas velocity distribution in the lower zone. Compared with the distributions with one or three injection layers, two injection layers produce more uniform gas flow. A small particle size of 6–15 mm increased the bed resistance and solid fraction standard deviation. A nozzle angle of 45° was conducive to increase the gas velocity in the upper zone and forming a more uniform gas distribution. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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14 pages, 5216 KiB  
Article
Numerical Simulation and Structural Optimization of Swirl Flow Micro-Nano Bubble Generator
by Xinkang Hu, Bo Zhang, Chundu Wu, Xiaohong Xu, Mingming Xue and Xiaoyong Zheng
Coatings 2023, 13(8), 1468; https://doi.org/10.3390/coatings13081468 - 21 Aug 2023
Viewed by 1468
Abstract
The development of the bubble generator that can efficiently generate micro-nano bubbles has always been recognized as a challenge. Swirling flow is considered to be an efficient method to enhance hydrodynamic cavitation. The vortex supply chamber and the variable-diameter accelerated vortex cavitation reaction [...] Read more.
The development of the bubble generator that can efficiently generate micro-nano bubbles has always been recognized as a challenge. Swirling flow is considered to be an efficient method to enhance hydrodynamic cavitation. The vortex supply chamber and the variable-diameter accelerated vortex cavitation reaction chamber were combined to obtain a stable high-speed tangential liquid flow and improve the cavitation effect inside the generator in this study. The central air intake column was innovatively installed above the cavitation reaction chamber, which prolonged the shear fracture time of bubbles under high shear force and improved the gas–liquid contact and mixing efficiency. The influence of geometric parameters on the internal and external flow fields of the generator was analyzed through the numerical simulation. The optimized central air intake column was located 10 mm above the inlet of the cavitation reaction chamber. The optimized variable diameter contraction angle was 16°, and the optimized generator outlet diameter was 15 mm. Through the bubble performance test, it was verified that the micro-nano bubbles with the minimum size and average size of 0.31 μm and 3.42 μm could be generated by the manufactured generator. The enforcement of the research provided theoretical guidance and data support for the development of efficient micro-nano bubble generators. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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21 pages, 79402 KiB  
Article
The Wetting Behavior of Water Droplets on Silane and Silane/GO-Modified Ettringite Surfaces: Insights into Molecular Dynamics Simulations
by Mengmeng Li, Heping Zheng, Yuying Duan, Dongshuai Hou, Pan Wang, Bo Pang, Shaochun Li and Zuquan Jin
Coatings 2023, 13(7), 1299; https://doi.org/10.3390/coatings13071299 - 24 Jul 2023
Viewed by 1029
Abstract
The use of rapid-hardening cementitious materials for the emergency repair of critical infrastructure in coastal environments is becoming increasingly widespread, and concrete surface hydrophobic protection treatment is equally necessary to improve the durability of both new and old concrete. Among them, silane-based hydrophobic [...] Read more.
The use of rapid-hardening cementitious materials for the emergency repair of critical infrastructure in coastal environments is becoming increasingly widespread, and concrete surface hydrophobic protection treatment is equally necessary to improve the durability of both new and old concrete. Among them, silane-based hydrophobic materials play an important role in concrete hydrophobic protection. Graphene oxide (GO)-modified silane materials can significantly improve the hydrophobic performance of coatings, but the hydrophobic mechanism of coatings modifying the sulfoaluminate cement’s main hydration product ettringite (AFt) has not yet been explored. In this study, molecular dynamics simulations were conducted to investigate the wetting properties of water droplets on the surface of AFt, isobutyltriethoxy silane (IBTS)-modified AFt, and IBTS/GO-modified AFt. It was found that the AFt substrate had good hydrophilicity, and the droplets could wet the interface through Ca-O ionic bonds and H-bonds. The IBTS coating initially impeded droplet wetting, but the adsorption stability of IBTS on the AFt substrate surface was poor under droplet action, leading to droplet penetration and dispersion of the IBTS coating on the AFt surface. However, the IBTS/GO coating significantly restricted droplet wetting due to the stable adsorption of GO on the AFt surface and the strong stability of hydrogen bonds between IBTS and GO. In conclusion, selecting a suitable bridging material between AFt and silane is crucial for improving the hydrophobic stability of silane coatings on sulfoaluminate cement materials. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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24 pages, 3314 KiB  
Article
Influence of Drop Viscosity and Surface Wettability on Impact Outcomes
by Ghokulla Haran Krishnan, Kevin Fletcher and Eric Loth
Coatings 2023, 13(5), 817; https://doi.org/10.3390/coatings13050817 - 23 Apr 2023
Cited by 2 | Viewed by 1697
Abstract
To understand the effects of liquid viscosity and surface wettability on the outcomes for a drop impacting perpendicularly on a dry, clean surface at a normal temperature and pressure, experiments were conducted for a wide variety of droplets and substrate surfaces. These experiments [...] Read more.
To understand the effects of liquid viscosity and surface wettability on the outcomes for a drop impacting perpendicularly on a dry, clean surface at a normal temperature and pressure, experiments were conducted for a wide variety of droplets and substrate surfaces. These experiments included a range of receding contact angles (from ~18° to ~150°) and liquid viscosities (from 1 cp to 45 cp); the broadest such combination is yet published. The surface wettabilities were quantitatively characterized using a new set of definitions: superphillic (θrec < 30°), phillic (30° < θrec < 90°), phobic (90° < θrec < 150°), and superphobic (θrec > 150°). Six different outcome regimes were found (including a new beaded deposition outcome) as a function of Ohnesorge number, Weber number, and the cosine of the receding contact angle. The beaded deposition is a hybrid of the well-known splash and deposition outcomes. The critical Weber number that separates the outcome boundaries was found to be significantly influenced by both the Ohnesorge numbers and the receding contact angle. In particular, there is a consistent reduction in the critical Weber number from superphilic to philic to neutral wettability conditions. Interestingly, this same decreasing trend line continues from neutral to phobic to superphobic conditions, but instead, it separates the regimes of deposition and bouncing. At higher Weber numbers, an additional boundary regime was found between splashing and bounce, which also decreased as the surface wettability decreased. This same type of trend was seen for several Ohnesorge numbers, indicating that wetting characterization should be based on the contact angles for the combination of the droplet liquid and the surface. In addition, a new regime map for droplet rebound on superphobic surfaces was obtained from the present and previous results indicating (for the first time) that the total rebound generally occurs for Weber numbers between 2.2 and 32 with Ohnesorge numbers less than 0.17. Additional studies are recommended to explore an even broader range of test conditions (especially intermediate wettability conditions), the separate influence of advancing and/or hysteresis contact angles, and to include the effects of the inclination angle, gas pressure, and heat transfer. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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13 pages, 4041 KiB  
Article
The Influence of Electric and Magnetic Fields on the Structure of Flat Drops of Magnetic Fluids upon Drying
by Yury I. Dikansky, Sofia A. Semenova and Andrey S. Drozdov
Coatings 2023, 13(3), 540; https://doi.org/10.3390/coatings13030540 - 02 Mar 2023
Cited by 1 | Viewed by 1176
Abstract
Drop casting is a widely used approach for surface modification and the creation of functional coatings. Drying of sessile droplets is often associated with a so-called coffee-ring effect which originates from a non-uniform evaporation rate in the liquid–air and results in the formation [...] Read more.
Drop casting is a widely used approach for surface modification and the creation of functional coatings. Drying of sessile droplets is often associated with a so-called coffee-ring effect which originates from a non-uniform evaporation rate in the liquid–air and results in the formation of non-planar deposits. In the last two decades, this phenomenon attracted a lot of attention as a potential approach towards surface modification and structuring, resulting in an increased interest to control the morphology of the formed deposits. Here, we describe the effect of magnetic and electric fields individually and in combination on the processes of deposit formation for drops of water- or kerosene-based magnetic fluids. For the water-based fluid, the relative inner deposit density showed a linear dependence on the applied electric potential in the range from −5 to +5 V and varied from 100% to 31%, while kerosene-based fluid did not respond to the electric field. The combination of electric and magnetic fields allowed more complex control over the morphology of the deposits and to separate the annular deposit from the main one by the rim up to 0.3 mm. The theoretical basis behind the observed effects is discussed. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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12 pages, 3092 KiB  
Article
Flow Characteristics and Hydraulic Lift of Coandă Effect-Based Pick-Up Method for Polymetallic Nodule
by Hao Jia, Jian Yang, Xianghui Su, Yapeng Wang and Kexin Wu
Coatings 2023, 13(2), 271; https://doi.org/10.3390/coatings13020271 - 25 Jan 2023
Cited by 6 | Viewed by 1099
Abstract
The deep-sea mining vehicle is the main component of the undersea exploitation system, which gathers polymetallic nodules with its professionally designed seabed collector. The Coandă effect-based collecting method is an improved hydraulic method that forms an adverse pressure gradient over the nodules by [...] Read more.
The deep-sea mining vehicle is the main component of the undersea exploitation system, which gathers polymetallic nodules with its professionally designed seabed collector. The Coandă effect-based collecting method is an improved hydraulic method that forms an adverse pressure gradient over the nodules by performing wall jet flow over a rounded convex surface. In comparison to the circular cylinder surface, the effect of wall jet over the logarithmic spiral surface has a self-preserving nature, which can be advantageous to the nodule collecting. However, this effect on lift capability has seldom been studied before. In the present investigation, a reduced form modelling jet flows over logarithmic spiral surfaces was performed to study the flow characteristics and lift ability of the newly designed Coandă effect-based collector. The jet-half width has been optimized to study the influence of wall curvature on the growth rate. The lift ability was found to be stronger with larger jet exit velocity, local curvature, or non-dimensional jet slot height. The growth rate, which represents the width of the main jet flow, went up in proportion to the downstream distance. The lift capability of jet flow in logarithmical spiral of x/R = 1 is significantly better than that of x/R = 2/3. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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15 pages, 3921 KiB  
Article
Experimental Investigation on Effects of Flow Orientation on Interfacial Structure of Air–Water Two-Phase Flow
by Shouxu Qiao, Jinyang Li, Jiaxing Ren and Seungjin Kim
Coatings 2023, 13(1), 5; https://doi.org/10.3390/coatings13010005 - 20 Dec 2022
Viewed by 1321
Abstract
This study focusses on investigating the effect of flow orientation on global and local two-phase flow parameters under two-phase flow conditions. Flow visualization, pressure measurement, and conductivity probe measurements are performed in a test facility made of 50.8 mm inner diameter acrylic pipes [...] Read more.
This study focusses on investigating the effect of flow orientation on global and local two-phase flow parameters under two-phase flow conditions. Flow visualization, pressure measurement, and conductivity probe measurements are performed in a test facility made of 50.8 mm inner diameter acrylic pipes with flow visualization, pressure measurement, and conductivity probe measurement. Characteristics of flow regimes and interfacial structures, and frictional pressure drop prediction in the vertical upward and vertical downward two-phase flows are compared and analyzed. The results show that unique coring phenomenon and slug bubbles with off-centered noses appear in the vertical downward flow. The flow regime transition boundaries shift to the lower gas superficial velocities in the vertical downward flow compared to that in the vertical upward flow. Furthermore, the distribution and one-dimensional transport of the void fraction, interfacial area concentration, bubble velocity, bubble Sauter-mean diameter, and bubble frequency are acquired and compared to study the effect of flow orientation on interfacial structures. The interfacial structure and its development are found to be mainly affected by the lift force and the turbulence related bubble interactions. The frictional pressure drop is acquired and modeled by the Lockhart–Martinelli correlation. The frictional pressure drop is found to be larger in the vertical upward flow than that in the vertical downward flow. The recommended C value for both vertical upward and vertical downward flows are proposed. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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20 pages, 9081 KiB  
Article
The Initial Corrosion Behavior of 20# Steel under the CO2/Aqueous Solution Gas–Liquid Two-Phase Bubble Flow Condition
by Guirong Yang, Wenming Song, Zhaoxia Pan, Ying Ma and Yuan Hao
Coatings 2022, 12(12), 1945; https://doi.org/10.3390/coatings12121945 - 11 Dec 2022
Viewed by 821
Abstract
The initial corrosion behavior of 20# steel under the condition of gas–liquid (CO2/aqueous solution) two-phase bubble flow was studied through weight loss, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results showed that the corrosion rate decreased rapidly [...] Read more.
The initial corrosion behavior of 20# steel under the condition of gas–liquid (CO2/aqueous solution) two-phase bubble flow was studied through weight loss, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results showed that the corrosion rate decreased rapidly when the corrosion time was less than 3 h, increased rapidly, even to 19.4% of the initial corrosion rate, when the corrosion time was from 3 h to 5 h, and then decreased slowly to about 63% of the initial corrosion rate after the corrosion time exceeded 5 h under different CO2 pressure conditions. The corrosion happened first at the defects area with a high activity such as the cross points of scratches, gradually formed corrosion pits, and then extended around until the corrosion products covered the whole pipe wall surface. At the beginning stage of the corrosion process, the corrosion products were composed of acicular corrosion products and a small number of flocculent corrosion products and formed the corrosion product layer with micro-cracks. With the extension of the corrosion time, the spherical corrosion particles started to form on the initial corrosion product layer’s surface and gradually covered the initial corrosion product layer completely. The whole corrosion product layer with dual-structure characteristics formed. The inner corrosion product sub-layer was composed of initial corrosion products with columnar characteristics from the cross-section perspective, and the outer corrosion product sub-layer was composed of spherical corrosion products that were relatively dense. There was no obvious interface between the inner columnar sub-layer and the dense outer sub-layer. As time went on, the corrosion product particles with a broccoli shape characteristic formed on the dual-structure corrosion product layer’s surface and finally formed the outermost layer of the whole corrosion product layer. In the end, the whole corrosion product layer with three sub-layers formed, namely, the columnar bottom sub-layer, the relatively dense middle sub-layer, and the surface dense sub-layer composed of particles with a broccoli shape. The main components of the corrosion products were Fe, C, and O, and the main phases of the corrosion products were Fe3C, FeCO3, Fe3O4, Fe2O3, and FeOOH. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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14 pages, 7647 KiB  
Article
Research on the Influence of Process Parameters on the Flow Field in Mold
by Fengming Du, Jian Zhao, Yue Zheng, Tianyi Li and Gengtao Zheng
Coatings 2022, 12(10), 1547; https://doi.org/10.3390/coatings12101547 - 14 Oct 2022
Cited by 1 | Viewed by 847
Abstract
The mold is one of the core components of steelmaking, and its flow field distribution will directly affect the quality of the casting slab. A three-dimensional nozzle model is built in this work, and fluid simulation is carried out to investigate the influence [...] Read more.
The mold is one of the core components of steelmaking, and its flow field distribution will directly affect the quality of the casting slab. A three-dimensional nozzle model is built in this work, and fluid simulation is carried out to investigate the influence of the casting speed, immersion depth, slab thickness, and width on flow behavior in the mold. This model combined simulation with real conditions. The casting speed, immersion depth, slab width, and slab thickness are the actual process parameters used in the steel factory. The results show that when the casting speed increases from 0.6 to 1.0 m/min, the strike positions of the narrow surface are 0.439, 0.476, and 0.480 m below the liquid level, respectively. When the immersion depth increases from 180 to 220 mm, the impact depth of the stream at the exit of the nozzle side hole moves down, the lower recirculation zone moves to the centre and bottom of the slab, and the upper recirculation zone moves downward. When the slab thickness increases, the strike locations of the narrow face move down. Further, when the slab width increases, the distance of the strike location from the strike position increases first and then decreases. From the fluid results, the process parameters can be optimized by considering the strike location and the change of the surface turbulent kinetic energy. The model proposed in this work provides a theoretical guidance and optimization for the nozzle. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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11 pages, 8417 KiB  
Article
Effect of Microstructure on Mechanical Properties of 316 LN Austenitic Stainless Steel
by Kewei Fang, Kunjie Luo and Li Wang
Coatings 2022, 12(10), 1461; https://doi.org/10.3390/coatings12101461 - 04 Oct 2022
Cited by 2 | Viewed by 2052
Abstract
The microstructure development of 316 LN austenitic stainless steel (316 LNSS) during the aging process is investigated in this article. The thermal aging processes were conducted at 750 °C with different periods ranging from 50 to 500 h. The metallographic results show that [...] Read more.
The microstructure development of 316 LN austenitic stainless steel (316 LNSS) during the aging process is investigated in this article. The thermal aging processes were conducted at 750 °C with different periods ranging from 50 to 500 h. The metallographic results show that the coherent and incoherent twins were present in the original 316 LNSS grains, but dwindled as the aging period increased. After 50 h of aging, many fine, dispersed particles precipitated from the matrix, which were identified as M23C6 by energy dispersive spectrometer (EDS) and transmission electron microscopy (TEM). Additionally, the impact toughness and Brinell hardness (HBW) changed during the aging, which was closely related to the effects of dispersion strengthening and solution strengthening. A negatively linear relationship between Brinell hardness and Charpy impact energy was established, which could be utilized to predict the degree of thermal embrittlement. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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21 pages, 35519 KiB  
Article
Numerical Simulation of Acid Gas Distribution and Corrosion Characteristics in Connecting Pipe of Lean/Rich Amine Heat Exchanger
by Zeyang Shi, Jianjun Lv, Zhipeng E, Peixu Wei, Yukuan Gu, Yuge Li, Wenming Song, Yuan Yan, Liping Wei and Jun Hu
Coatings 2022, 12(10), 1460; https://doi.org/10.3390/coatings12101460 - 03 Oct 2022
Cited by 1 | Viewed by 1347
Abstract
In the high sulfur natural gas purification unit, the connecting pipe of a lean/rich amine heat exchanger is extremely susceptible to corrosion due to the acid gas and amine liquid condition. This work numerically investigated the gas–liquid flow and corrosion of the real-scale [...] Read more.
In the high sulfur natural gas purification unit, the connecting pipe of a lean/rich amine heat exchanger is extremely susceptible to corrosion due to the acid gas and amine liquid condition. This work numerically investigated the gas–liquid flow and corrosion of the real-scale connecting pipeline with two horizontal sections, one vertical section and four elbow sections. The effect of acid gas holdup on the gas–liquid flow pattern, distribution of velocity and pressure, and corrosion rate was investigated using an experimental validated model. With an increase in the acid gas fraction from 0.03 to 0.12, the flow pattern of the horizontal section changes from bubbly flow to a stratified flow in the horizontal section, while the flow pattern of the vertical section and elbow section keeps bubbling, and the proportion of gas bubbles increases in the vertical section and all elbow sections. The maximum pressure gradient was observed on the top of the horizontal section. The most serious corrosion section was found out on the outlet of the first elbow section where the gas liquid flow starts to stratify, which is consistent with the measured minimum wall thickness. A solution measure for anti-corrosion acid gas in the pipeline was proposed by adding a bifurcated pipe to separate the acid gas in the first horizontal section. The accumulated acid gas was effectively thrown out from the outlet of the bifurcated pipe. This method provides a promising way to eliminate the acid gas in the pipe and avoid forming stratified flow, which is helpful for prolonging the service life of the pipe. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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12 pages, 4753 KiB  
Article
Intelligent Evaluation of Marine Corrosion of Q420 Steel Based on Image Recognition Method
by Kai Wang, Chenpei Li, Jinling Lu, Cuihong Nan, Qiaoling Zhang and Hao Zhang
Coatings 2022, 12(7), 881; https://doi.org/10.3390/coatings12070881 - 22 Jun 2022
Cited by 6 | Viewed by 1417
Abstract
Marine engineering materials are prone to serious corrosion damage, which affects the efficiency and reliability of marine equipment. The diversity of corrosion morphology makes it difficult to achieve the quantification and standardization of the microscopic local information on the corroded surface, which is [...] Read more.
Marine engineering materials are prone to serious corrosion damage, which affects the efficiency and reliability of marine equipment. The diversity of corrosion morphology makes it difficult to achieve the quantification and standardization of the microscopic local information on the corroded surface, which is of great significance to reveal the multi-scale corrosion mechanism. In this paper, an image intelligent recognition method for the corrosion damage of Q420 steel in seawater is established, which is based on the gray level co-occurrence matrix, binary image method and fractal model. Through the feature extraction of corrosion morphology, the quantitative analysis of corrosion morphology and the microscopic evaluation of corrosion characteristics are achieved. The image recognition data are consistent with the electrochemical result for most cases, which confirms the validity of this image intelligent recognition method. The average gray value and energy value of corrosion morphology reduces with the Cl− concentration, indicating that the corrosion damage aggravates gradually. The increasing standard deviation and entropy reflects that the randomness of the pit distribution increases. The pitting ratio increases from 20.19% to 51.64% as the Cl− concentration increases from 50% to 200% of the standard solution. However, there exists a discrepancy for high Cl− concentration because of the irregular corrosion morphology and various pit depth. The fractal dimension increases with the complexity of the corroded surface at low Cl− concentration, but the fractal dimension decreases at high Cl− concentration because the corrosion complexity is interfered by the interconnection of corrosion holes due to the accelerated pit evolution. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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12 pages, 3869 KiB  
Article
The Effects of Nozzle Inclination, Area Ratio, and Side-Hole Aspect Ratio on the Flow Behavior in Mold
by Fengming Du, Tianyi Li and Gengtao Zheng
Coatings 2022, 12(6), 815; https://doi.org/10.3390/coatings12060815 - 10 Jun 2022
Cited by 2 | Viewed by 1425
Abstract
During the steel continuous casting, the submerged entry nozzle (SEN) plays a crucial role in the fluid characteristic of fluid steel, which further affects the slab quality. In this paper, a nozzle model is developed to study the influences of nozzle inclination, nozzle [...] Read more.
During the steel continuous casting, the submerged entry nozzle (SEN) plays a crucial role in the fluid characteristic of fluid steel, which further affects the slab quality. In this paper, a nozzle model is developed to study the influences of nozzle inclination, nozzle area ratio, and side hole aspect ratio on the fluid characteristic of fluid steel. The results show that when the nozzle angle increased from 10° to 20°, the impact points of the narrow surface were 0.402 m, 0.476 m, and 0.554 m away from the meniscus, respectively. In addition, when the nozzle area ratio increased from 0.96 to 1.16, it resulted in a significant decrease of the speed of high-temperature liquid steel flowing out of the nozzle. Moreover, when the side-hole aspect ratio was 1.47, the maximum turbulent kinetic energy of the free surface reached 0.00141 m2 s−2. Furthermore, when the aspect ratio was 1.67 and 1.84, a slight difference existed, and the maximum turbulent kinetic energy was almost 0.00095 m2 s−2. The proposed model can provide theoretical basis and guidance for nozzle optimization. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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11 pages, 2766 KiB  
Article
Influence of Nozzle Design on Flow Characteristic in the Continuous Casting Machinery
by Fengming Du, Tianyi Li, Yunbo Zeng and Kaiguang Zhang
Coatings 2022, 12(5), 631; https://doi.org/10.3390/coatings12050631 - 05 May 2022
Cited by 2 | Viewed by 1470
Abstract
In the process of continuous casting, the submerged nozzle will affect the flow of the liquid steel and the quality of the slab. In this paper, three nozzle structures are investigated to compare the influence of the nozzle structure on the flow and [...] Read more.
In the process of continuous casting, the submerged nozzle will affect the flow of the liquid steel and the quality of the slab. In this paper, three nozzle structures are investigated to compare the influence of the nozzle structure on the flow and solidification of steel. In addition, the flow field, flow velocity, recirculation zone, free-surface turbulent kinetic energy and heat transfer of fluid steel are calculated. The results demonstrate that among the three nozzles, the structure of the B nozzle is the best. The fluid steel flows out from the nozzle at a certain angle. The flow rate and momentum of the fluid steel gradually decrease, and two split streams are formed when the main stream approaches the narrow surface. The spherical area at the bottom of the nozzle can reduce the flow rate of the fluid steel at the outlet of the nozzle, leading to a stable liquid level. The turbulent kinetic energy of the free liquid surface of nozzle A is the largest, reaching 0.00204 m2·s−2. The turbulent kinetic energy of nozzle C is slightly lower (0.00193 m2·s−2), and the free-liquid-surface turbulent kinetic energy of nozzle B (0.00154 m2·s−2) is the smallest. The surface velocity of nozzle B is also lower than that of A and C because the vortex center of the upper recirculation zone of nozzle B is closer to the narrow surface. The results show that the B nozzle is optimal, and this model can provide theoretical guidance for the design of a nozzle during the continuous casting. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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Review

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22 pages, 13995 KiB  
Review
Research Progress in Superhydrophobic Titanium-Based Implants for Antibacterial Applications
by Qin Rao, Ling Weng, Jinshuang Zhang, Donghao Liu, Wenjuan Zhang, Siyuan Chen, Jialong Chen, Xiangyang Li, Hua Qiu, Ying Cao, Quanli Li and Shunli Zheng
Coatings 2023, 13(2), 419; https://doi.org/10.3390/coatings13020419 - 12 Feb 2023
Cited by 4 | Viewed by 2627
Abstract
Titanium and its alloys have been extensively used as implant materials in clinic settings. However, implant-associated bacterial infection or inflammation remains a primary cause of implantation failure, which threatens human health, and has already become a global issue. Recently, a superhydrophobic surface endowed [...] Read more.
Titanium and its alloys have been extensively used as implant materials in clinic settings. However, implant-associated bacterial infection or inflammation remains a primary cause of implantation failure, which threatens human health, and has already become a global issue. Recently, a superhydrophobic surface endowed with a water contact angle higher than 150° has attracted widespread attention in antibacterial applications for their self-cleaning and low-adhesion properties, which has emerged as an important path in preventing biofilm formation. This review first describes the basic theories of wettability. In the second section, we explain biofilm formation, which is a primary pathogenic occurrence in the development of infection in implants. In the last and most important section, we summarize the progress of superhydrophobic titanium-based implants and recent antibacterial applications. This review will attract great interest from both research scientists and clinicians, which will help to rapidly expand superhydrophobic titanium-based implants for antibacterial applications. Full article
(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)
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