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The advancement of experimental methods has provided new information about the structure and structural fluctuations of water. Despite the appearance of numerous models, which aim to describe a wide range of thermodynamic and electrical characteristics of water, there is a deficit in systemic understanding of structuring in aqueous solutions. A particular challenge is the fact that even pure water is a heterogeneous, multicomponent system composed of molecular and supramolecular structures. The possibility of the existence of such structures and their nature are of fundamental importance for various fields of science. However, great difficulties arise in modeling relatively large supramolecular structures (e.g. extended hydration shells), where the bonds between molecules are characterized by low energy. Generally, such structures may be non-equilibrium but relatively long-lived. Evidently, the short times of water microstructure exchanges do not mean short lifetimes of macrostructures, just as the instability of individual parts does not mean the instability of the entire structure. To explain this paradox, we review the data from experimental and theoretical research. Today, only some of the experimental results on the lifetime of water structures have been confirmed by modeling, so there is not a complete theoretical picture of the structure of water yet. We propose a new hierarchical water macrostructure model to resolve the issue of the stability of water structures. In this model, the structure of water is presented as consisting of many hierarchically related levels (the stratification model). The stratification mechanism is associated with symmetry breaking at the formation of the next level, even with minimal changes in the properties of the previous level. Such a hierarchical relationship can determine the unique physico-chemical properties of water systems and, in the future, provide a complete description of them. [ABSTRACT FROM AUTHOR]

The measurement of mixing time in a water model of soft-stirring steelmaking ladles is practically facing a problem of bad repeatability. This uncertainty severely affects both the understandings of transport phenomenon in ladles and the measurement accuracy. Scaled down by a ratio of 1:4, a water model based on an industrial 260-ton ladle is used. This paper studies the transport process paths and mixing time of salt solution tracers in the water model of eccentric gas-stirred ladles with a low gas flow rate. After a large number of repeated experiments, the different transport paths of the tracer and the error of the mixing time in each transport path are discussed and compared with the numerical simulation results. The results of a large number of repeated experiments on the water model show that there are five transport paths for the tracer in the ladle. The tracer of the first path is mainly transported by the left-side main circulation flow, which is identical to the numerical simulation results. The tracer of the second and third paths are also mainly transported by the left-side circulation flow, but bifurcations occur when the tracer in the middle area is transported downward. In the third path, the portion and intensity of the tracer transferring to the right side from the central region is higher than in the second path. The fourth path is that the tracer is transported downward from the left, middle, and right sides with a similar intensity at the same time. While the tracer in the fifth path is mainly transported on the right side, and the tracer forms a clockwise circulation flow on the right side. The mixing times from the first transport path to the fifth transport path are 158.3 s, 149.7 s, 171.7 s, 134 s and 95.7 s, respectively, among which the third transport path and the fifth transport path are the maximum and minimum values among all transport paths. The error between the mixing time and the averaged mixing time at each monitoring point in the five transport paths of the tracer is between −34.7% and 40.9%. Furthermore, the error of the averaged mixing time of each path and the path-based average value is between 5.5% and 32.6%. [ABSTRACT FROM AUTHOR]

The investigation of the compounding mechanisms of mixed collectors in low-rank coal flotation has gradually progressed from a macro to a micro level, and the accuracy of research outcomes significantly depends on the development of micro models. While All-Atom Molecular Dynamics (AAMD) simulations have been used for this purpose, the employment of an excessive amount of collector in the system leads to a failure in replicating the actual flotation process, which in turn, limits the practical applicability of research findings. To overcome this drawback, this paper suggests using the MARTINI Coarse-Grained force field (CGFF), developed by the S.J.Marrink group, to construct a simulation system that accurately mimics the amount of collector employed in practical flotation processes. In light of this, to make the MARTINI force field more applicable for research in the low-rank coal field, we employ density functional theory (DFT) and coarse-grained molecular dynamics (CGMD) methods to investigate water cluster interactions, identify magic number clusters, and fit the corresponding CGFF parameters to develop a CG water model suitable for exploring the compounding mechanism of mixed collectors. This research lays the groundwork for future investigations into the aggregation behavior of mixed collectors under actual usage conditions, as well as their synergistic adsorption at the coal/water interface. [ABSTRACT FROM AUTHOR]

The advancement of experimental methods has provided new information about the structure and structural fluctuations of water. Despite the appearance of numerous models, which aim to describe a wide range of thermodynamic and electrical characteristics of water, there is a deficit in systemic understanding of structuring in aqueous solutions. A particular challenge is the fact that even pure water is a heterogeneous, multicomponent system composed of molecular and supramolecular structures. The possibility of the existence of such structures and their nature are of fundamental importance for various fields of science. However, great difficulties arise in modeling relatively large supramolecular structures (e.g. extended hydration shells), where the bonds between molecules are characterized by low energy. Generally, such structures may be non-equilibrium but relatively long-lived. Evidently, the short times of water microstructure exchanges do not mean short lifetimes of macrostructures, just as the instability of individual parts does not mean the instability of the entire structure. To explain this paradox, we review the data from experimental and theoretical research. Today, only some of the experimental results on the lifetime of water structures have been confirmed by modeling, so there is not a complete theoretical picture of the structure of water yet. We propose a new hierarchical water macrostructure model to resolve the issue of the stability of water structures. In this model, the structure of water is presented as consisting of many hierarchically related levels (the stratification model). The stratification mechanism is associated with symmetry breaking at the formation of the next level, even with minimal changes in the properties of the previous level. Such a hierarchical relationship can determine the unique physico-chemical properties of water systems and, in the future, provide a complete description of them.

Inclusions are one of the important factors affecting the cleanliness of molten steel. The current optimization of inclusion removal methods mainly focuses on promoting inclusions to float to the slag–steel interface so that the inclusions can be absorbed and removed by the refining slag. However, the research on the floating removal of inclusions cannot be carried out directly in the ladle, so methods such as mathematical models and physical models were developed. This article uses silicone oil to simulate the slag layer; polypropylene particles; and aluminum oxide particles to simulate inclusions to establish a water model experiment. By changing the viscosity of silicone oil and the diameter of particles, the factors affecting the movement of inclusions at the slag–steel interface were explored. Based on the water model, a mathematical model of the floating behavior of inclusions at the slag–steel interface was constructed, and parameters such as particle diameter and interfacial tension in the water model experiment were studied by the mathematical model for calculation. Both the mathematical model and the water model experimental results show that after the viscosity of silicone oil increases from 0.048 Pa·s to 0.096 Pa·s, the dimensionless displacement and terminal velocity of the particles decreases. When the diameter of the same particle increases, the dimensionless displacement and terminal velocity increases. The dimensionless displacement of polypropylene particles of the same diameter is larger than that of aluminum oxide particles, and the terminal velocity is smaller than that of aluminum oxide particles. This is attributed to the better overall three-phase wettability of polypropylene particle. When the liquid level increases, the dimensionless displacement and terminal velocity of particles under the same conditions show only slight differences (less than 10%). [ABSTRACT FROM AUTHOR]

Silicon steel (electrical steel) has been used in electric motors that are important components in sustainable new energy Electrical Vehicles (EVs). The Ruhrstahl–Heraeus process is commonly used in the refining process of silicon steel. The refining effect inside the RH degasser is closely related to the flow and mixing of molten steel. In this study, a 260 t RH was used as the prototype, and the transport process of the passive scalar tracer (virtual tracer) and salt tracer (considering density effect) was studied using numerical simulation and water model research methods. The results indicate that the tracer transports from the up snorkel of the down snorkel to the bottom of the ladle, and then upwards from the bottom of the ladle to the top of the ladle. Density and gravity, respectively, play a promoting and hindering role in these two stages. In different areas of the ladle, density and gravity play a different degree of promotion and obstruction. Moreover, in different regions of the ladle, the different circulation strength leads to the different promotion degrees and obstruction degrees of the density. This results in the difference between the concentration growth rate of the salt tracer and the passive scalar in different regions of the ladle top. From the perspective of mixing time, density and gravity have no effect on the mixing time at the bottom of the ladle, and the difference between the passive scalar and NaCl solution tracer is within the range of 1–5%. For a larger dosage of tracer case, the difference range is reduced. However, at the top of the ladle, the average mixing time for the NaCl solution case is significantly longer than that of the passive scalar case, within the range of 3–14.7%. For a larger dosage of tracer case, the difference range is increased to 17.4–41.1%. It indicates that density and gravity delay the mixing of substances at the top area of the ladle, and this should be paid more attention when adding denser alloys in RH degasser. [ABSTRACT FROM AUTHOR]

In previous research simulating steelmaking ladles using cold water models, the dosage/volume of the salt tracer solution is one of the factors that has been overlooked by researchers to a certain extent. Previous studies have demonstrated that salt tracers may influence the flow and measured mixing time of fluids in water models. Based on a water model scaled down from an industrial 130-ton ladle by a ratio of 1:3, this study investigates the impact of salt tracer dosage on the transport and mixing of tracers in the water model of gas-stirred ladle with a moderate gas flow rate. A preliminary uncertainty analysis of the experimental mixing time is performed, and the standard deviations were found to be less than 15%. It was observed in the experiments that the transport paths of tracers in the ladle can be classified into two trends. A common trend is that the injected salt solution tracer is asymmetrically transported towards the left sidewall of the ladle by the main circulation. In another trend, the injected salt solution tracer is transported both by the main circulation to the left side wall and by downward flow towards the gas column. The downward flow may be accelerated and become a major flow pattern when the tracer volume increases. For the dimensionless concentration curve, the sinusoidal type, which represents a rapid mixing, is observed at the top surface monitoring points, while the parabolic type is observed at the bottom monitoring points. An exception is the monitoring point at the right-side bottom (close to the asymmetric gas nozzle area), where both sinusoidal-type and parabolic-type curves are observed. Regarding the effect of tracer volume on the curve and mixing time, the curves at the top surface monitoring points are less influenced but curves at the bottom monitoring points are noticeably influenced by the tracer volume. A trend of decreasing and then increasing as the tracer volume increases was found at the top surface monitoring points, while the mixing times at the bottom monitoring points decrease with the increase in the tracer volume. [ABSTRACT FROM AUTHOR]

The measurement of mixing time in a water model of soft-stirring steelmaking ladles is practically facing a problem of bad repeatability. This uncertainty severely affects both the understandings of transport phenomenon in ladles and the measurement accuracy. Scaled down by a ratio of 1:4, a water model based on an industrial 260-ton ladle is used. This paper studies the transport process paths and mixing time of salt solution tracers in the water model of eccentric gas-stirred ladles with a low gas flow rate. After a large number of repeated experiments, the different transport paths of the tracer and the error of the mixing time in each transport path are discussed and compared with the numerical simulation results. The results of a large number of repeated experiments on the water model show that there are five transport paths for the tracer in the ladle. The tracer of the first path is mainly transported by the left-side main circulation flow, which is identical to the numerical simulation results. The tracer of the second and third paths are also mainly transported by the left-side circulation flow, but bifurcations occur when the tracer in the middle area is transported downward. In the third path, the portion and intensity of the tracer transferring to the right side from the central region is higher than in the second path. The fourth path is that the tracer is transported downward from the left, middle, and right sides with a similar intensity at the same time. While the tracer in the fifth path is mainly transported on the right side, and the tracer forms a clockwise circulation flow on the right side. The mixing times from the first transport path to the fifth transport path are 158.3 s, 149.7 s, 171.7 s, 134 s and 95.7 s, respectively, among which the third transport path and the fifth transport path are the maximum and minimum values among all transport paths. The error between the mixing time and the averaged mixing time at each monitoring point in the five transport paths of the tracer is between −34.7% and 40.9%. Furthermore, the error of the averaged mixing time of each path and the path-based average value is between 5.5% and 32.6%.

The baffle effect of inserting a filter within a tundish was investigated using a combination of water model experiments and numerical simulations. The filter, which is a cost-effective device used to enhance the quality of molten steel by removing inclusions, was studied for its impact on the removal rate of inclusions. In the water model experiments, a scaled-down model of the tundish system was created with a geometric ratio of 1:4. Polyethylene particles of varying sizes were used to simulate the inclusions. Additionally, a three-dimensional numerical model of the water model was developed to validate the experimental findings, provide supplementary data for analysis, and propose an optimized tundish configuration by moving the weir away from the filter by 50, 100, and 150 mm. The flow patterns were also thoroughly examined. The results revealed that the presence of the filter increased the flow resistance within the tundish, leading to changes in the residence time distribution. This resulted in the formation of a 'dead zone' with a significantly prolonged residence time. The higher flow resistance hindered the entry and exit of particles from the last chamber of the tundish. As a result, the distribution of particles in the last chamber became more dispersed, reducing the detrimental effects of inclusions in the steel. The removal efficiency of the seven types of particles was improved by 2–7%. Furthermore, by moving the weir away from the filter by 50 mm, the removal ratio could be further increased by approximately 2%. [ABSTRACT FROM AUTHOR]

Purposes In ladle metallurgy, block or whole bag alloy materials and lime are usually added. In recent years, some companies have reported a new process of adding scrap steel to ladle refining furnace. Studying the melting and homogenization mechanism of the above solid substances in the ladle refining process can optimize the refining process and accelerate production rate. Methods Ice sample and ice sphere made by KCl solution were used in the water model experiment separately to study the mechanisms of motion, melting, and mixing of alloy in a 260 t ladle. These two samples were selected to simulate the light and heavy alloys respectively. The effects of factors such as temperature, bottom blowing flow rate, liquid level height, and addition position on the mechanicms were studied. Findings The results show that the melting time of both two ice samples decreases dramatically with increasing temperature. The melting process of light ice sample (ice sphere) can be obviously accelerated by increasing the gas flowrate. When the liquid level is high, i.e. the ratio of liquid level to the diameter is 1.1, the melting time of ice sphere is relative short. The melting of ice sphere can hardly be affected by its adding position. For the heavy ice sample (salt sphere), when added from a position which is far away from the nozzle, it stays at the bottom of the ladle and melts slowly. When the salt sphere is added above the nozzle, the chances of washing by the bubbles from plume area increase and the melting time is shortened. Increasing the gas flow rate can reduce the melting time of the salt sphere, and the liquid level has a negligible effect. When the salt sphere is scoured by the bubbles in plume area, the melting time and mixing time are shortened.

The submerged entry nozzle (SEN) plays an important role in the continuous casting production process. It is a cast refractory pipe fitting installed in the lower part of the tundish and inserted below the molten steel level of the mold. It not only affects the speed of molten steel flow, but is also prone to nodules and affects production. In the present work, the flow behavior of molten steel in a traditional nozzle and that in a new type of nozzle whose inner wall was distributed with arrays of hemispherical crowns were studied by means of both physical simulation (using a water model) and numerical simulation (using ANSYS CFX) based on the prototype of a production continuous casting slab mold. Both experimental and numerical simulation results show that, compared with the traditional nozzle, the impact depth generated by the new-type nozzle in the mold is reduced by 21.06–26.03 cm, the impact angle is reduced by 14–17 degrees, and swirl flow was generated inside the new-type nozzle, which not only improves the flow characteristics inside the submerged entry nozzle and changes the dead zone size in the submerged entry nozzle, but also improves the velocity distribution at the outlet of the nozzle and minimizes the possibility of nodulation. In addition, in contrast to the traditional nozzle that generates flat body-shaped jets of molten steel flow, the new-type nozzle produces baseball glove-shaped jets that penetrate shallower into the molten steel bath in the mold, which significantly reduces the outlet velocity and is conducive to the floating of inclusions. [ABSTRACT FROM AUTHOR]

The growing demand of high-quality casting is driving the use of ceramic foam filters in casting processes. The primary purpose of using a filter in a casting process is to remove impurities from the molten metal and to stabilize the flow of molten metal by slowing the flow rate. However, only a few studies have been conducted on the specific effects of ceramic foam filters on fluid flow during the casting process. In this study, a water model equipment is used to study the effect of ceramic foam filters on fluid flow, and commercial filters from three domestic and foreign companies are used. The reliability of the data obtained from the water model experiment is verified by an actual casting experiment. Finally, with the verified water model experimental data, the filter is modeled, and a computational fluid simulation is conducted to study the effect of the installation location of the filter on the casting. [ABSTRACT FROM AUTHOR]

A two-dimensional water model was used to simulate the process of combined blowing. The effect of boundary conditions on the size and coordinate distribution of the dispersed phase was investigated. The results showed that the frequency of the dispersed phase at a certain size level is proportional to its size; the coordinates of the dispersed phase can be expressed in a dimensionless form that shows its uniformity of distribution. An empirical equation for the influence of the boundary conditions on the size and coordinate distribution of the dispersed phase in combined blowing process is also presented. [ABSTRACT FROM AUTHOR]

To investigate slag carryover in the last stage of ladle teeming during continuous casting, a water model system was established. The nozzle flow rate of model ladle was controlled by slide gate, which was automatically governed by a control module. The prototype teeming process can be accurately modelled through the system. However, under the condition that the slide gate is fully opened, the teeming process in water model has a great deviation with the actual. The vortex critical height in the mode of dynamic changing of slide gate is obviously less than that under the condition of 100% opening. Furthermore, under the dynamic changing mode, effects of operating parameters on vortex formation and slag carryover have been investigated. The vortex critical height decreases as the residence time before teeming increases. The effect of initial water level on critical height of vortex is little. As the flow rate increases, the critical height of vortex increases significantly. The variation of vortex diameter experiences developing stage and matured stage. When oil is added into model ladle, an important change is that the critical height of vortex decreases. By contrast, the vortex diameter obviously increases. The vortex critical height decreases while oil is added into ladle, but it increases as the oil layer thickness increases.

In previous research simulating steelmaking ladles using cold water models, the dosage/volume of the salt tracer solution is one of the factors that has been overlooked by researchers to a certain extent. Previous studies have demonstrated that salt tracers may influence the flow and measured mixing time of fluids in water models. Based on a water model scaled down from an industrial 130-ton ladle by a ratio of 1:3, this study investigates the impact of salt tracer dosage on the transport and mixing of tracers in the water model of gas-stirred ladle with a moderate gas flow rate. A preliminary uncertainty analysis of the experimental mixing time is performed, and the standard deviations were found to be less than 15%. It was observed in the experiments that the transport paths of tracers in the ladle can be classified into two trends. A common trend is that the injected salt solution tracer is asymmetrically transported towards the left sidewall of the ladle by the main circulation. In another trend, the injected salt solution tracer is transported both by the main circulation to the left side wall and by downward flow towards the gas column. The downward flow may be accelerated and become a major flow pattern when the tracer volume increases. For the dimensionless concentration curve, the sinusoidal type, which represents a rapid mixing, is observed at the top surface monitoring points, while the parabolic type is observed at the bottom monitoring points. An exception is the monitoring point at the right-side bottom (close to the asymmetric gas nozzle area), where both sinusoidal-type and parabolic-type curves are observed. Regarding the effect of tracer volume on the curve and mixing time, the curves at the top surface monitoring points are less influenced but curves at the bottom monitoring points are noticeably influenced by the tracer volume. A trend of decreasing and then increasing as the tracer volume increases was found at the top surface monitoring points, while the mixing times at the bottom monitoring points decrease with the increase in the tracer volume.

Herein, corundum porous permeable bricks with different coarse aggregate contents are prepared using particle packing method. Based on the similarity principle, a local water model of a tundish is designed to investigate the bubbling behavior in porous permeable bricks at various argon flow rates. Through dimensionless analysis, empirical formulas of bubbling region diameter and initial bubble size in porous permeable bricks are proposed. The results show that an increasing aggregate content can increase the apparent porosity and the proportion of large pores, reduce the surface fractal dimension of the porous permeable bricks, and obtain a higher gas permeability. With the increase of argon flow rate and the decrease of gas permeability, the internal pressure gradient in porous permeable bricks increases. The larger the argon flow rate and the gas permeability value, the more beneficial it is to activate more pores and form a larger bubbling region on the upper surface of porous permeable bricks. The Sauter mean diameter of bubbles and the initial velocity of gas plumes are inversely correlated with the content of coarse aggregate; that is, the porous permeable brick with a higher content of coarse aggregate is beneficial to generating much more small bubbles. [ABSTRACT FROM AUTHOR]

A previously unnoticed anomaly is recently identified in a stopper rod flow control system for the continuous casting of steel by comparing full‐scale water model experiments with plant data. Despite extensive research previously done on the continuous casting fluid flow phenomena, this anomaly and its background physics are not well understood by researchers. Computational fluid dynamics (CFD) modeling of the molten steel flow in the stopper rod system is performed with predictions matching closely with water model data but deviating from plant measurements. It is thus suggested by this comparison that certain aspects of the liquid steel flow and pressure behavior in the stopper rod system cannot be effectively described by traditional modeling techniques due to their embedded limitations. Through water modeling, CFD simulations, plant measurements, and theoretical analysis, the current study for the first time presents a thorough discussion of this observed anomaly, which brings new insights into understanding the complex fluid flow behavior and pressure distributions inside the stopper rod control system during the continuous casting process. [ABSTRACT FROM AUTHOR]

For the purpose of understanding the mechanism of grain refinement in cast metal by mechanical vibration, demonstration tests were conducted using an ammonium chloride solution. Ammonium chloride solution and molds with various shape were prepared for the water model experiment. In the case of an open mold, ammonium chloride crystals crystallized on the mold wall and grew toward the center of the mold without vibration. However, when vibration was applied, countless crystals generated at the upper side of the solution immediately after pouring. In the case of a full plugged mold, no wave and convection occurred in the solution even when vibration was added, and the behavior seen was similar to the case without vibration. When only convection occurred in the full plugged mold, crystals were found to move from the mold wall into the solution. When a weir was set in the riser, it helped prevent the generation of crystals on the mold wall of the riser from migrating to the specimen. When a mold with a weir was used for Al2% Cu alloy, crystals in the specimen did not become refined as seen in the water model experiments. These results demonstrate that a large amount of crystals are generated at the boundary between the surface of the molten metal and mold wall when molten metal is vibrated, and these fine crystals fill into the mold due to sedimentation or convection, thereby achieving grain refinement. [ABSTRACT FROM AUTHOR]

We study the grain-size effect on mechanical behaviors of polycrystalline ice at nanoscale through large-scale molecular dynamics simulations, enabled by an accurate and efficient machine-learned coarse-grained water model [H. Chan, M. J. Cherukara, B. Narayanan, T. D. Loeffler, C. Benmore, S. K. Gray and S. K. Sankaranarayanan. Machine learning coarse grained models for water. Nature Communications 10(1), p. 379, 2019]. Polycrystalline ice systems with different grain sizes in the range of 5 ∼ 3 0 nm are systematically investigated through uniaxial tensile tests. Simulation results reveal that Young's modulus and yield strength increase as the grain size increases, leading to an inverse Hall–Petch effect in nanocrystalline ice. Such an observation is significantly different from the conventional Hall–Petch effect in polycrystalline ice observed by experiments at millimeter scale. The deformation behavior suggests that grain boundaries (GBs), rather than grain interiors, play the active role in accommodating external loading in nanocrystalline ice. Further void analysis of nanocrystalline ice during deformation reveals that nanocrack initiates and propagates along GBs and eventually leads to failure of systems with larger grain sizes (≥ 2 0 nm), yielding a sudden drop in the stress–strain curve. While for systems with smaller grain sizes (≤ 1 5 nm), only extensive plastic deformation is presented without significant void growth. Our simulation results demonstrate that the GB sliding is the governing mechanism for the inverse Hall–Petch effect observed in nanocrystalline ice. [ABSTRACT FROM AUTHOR]

In this paper, by changing the shape of the inner wall of the nozzle, a water model experiment was carried out on the slab with the section of 200 / mm × 1 200 / mm. The results show that under the same immersion depth and the same angle, the improved No.1 nozzle and the improved No.2 nozzle have swirling flow, which reduced the dead region and the internal longitudinal flow velocity, and the swirl ratio generated in improved No. 2 nozzle is more obvious than improved No. 1 nozzle. The impact depth of the velocity at the outlet of the improved No.2 nozzle is obviously lower than that of the original nozzle and the improved No.1 nozzle.

Ultra-wide slabs have a good application market and prospect, but there is still a lack of research on the flow field. To explore the characteristics of its flow field, this study built a 0.5-scale physical model of mold using Perspex. The effect of casting speed on flow field and surface flow speed was investigated by using an ink tracer experiment and contact measurement. There were various flow patterns in the ultra-wide slab mold, and they continue to transform each other. The jet momentum from the nozzle ports was diffused by colliding with the wide face, which lowered its kinetic energy and affected its subsequent diffusion. Compared with the conventional mold, the upper flow intensity of the ultra-wide slab mold was weaker, which made its liquid surface inactive and caused it to produce a flux rim or slag strip. At different casting speeds, the average flow speed distribution of the ultra-wide slab was C-shaped. When it increased from 0.9 to 1.4 m/s, the corresponding maximum average flow speed increased from 0.08 to 0.2 m/s. At the same time, the proportion of the low-flow speed zone at the most active part of the surface also gradually decreased from more than 90% to about 49%. [ABSTRACT FROM AUTHOR]

Bottom-blowing copper smelting is a bath smelting technology recently developed in China. It has the advantages of good adaptability of raw materials, high oxygen utilization and thermal efficiency, and flexible production capacity. Plume eye is a unique phenomenon observed in the bottom-blowing copper-smelting furnace where the slag on the surface of the bath is pushed away by the high-pressure gas injected from the bottom. The existence of plume eye was first confirmed by analyzing the quenched industrial samples collected above the gas injection area and then investigated by laboratory water model experiments. Combining the plant operating data and the smelting mechanism of the copper concentrate, the role of the plume eye in bottom-blowing-enhanced smelting is analyzed. It reveals that the direct dissolution of copper concentrate as a low-grade matte into the molten matte can significantly accelerate the reactions between the concentrate and oxygen. The productivity of the bottom-blowing furnace is therefore increased as a result. The effects of the gas flow rate and thickness of the matte and of the slag layer on the diameter of the plume eye were studied using water-model experiments. It was found that increasing the gas flow and the thickness of the matte and reducing the thickness of the slag can increase the diameter of the plume eye. This work is of great significance for further understanding the copper bottom-blowing smelting technology and optimizing industrial operations. [ABSTRACT FROM AUTHOR]

In deep penetration laser welding, the behavior of the keyhole has an important influence on the welding quality. As it is difficult to directly observe the keyhole and detect the pressure inside the keyhole during metal laser welding, theoretical analysis and numerical simulation methods are commonly used methods in studying keyhole behavior. However, these methods cannot provide direct real information on keyhole behavior. In this paper, a method of analogy welding is proposed, in which high speed gas is used to blow the liquid to generate the keyhole. Relevant process experiments were conducted to explore keyhole behavior in analogy welding and real deep penetration laser welding. The pressure balance of the keyhole, both in analogy welding and real deep penetration laser welding, were analyzed. The laws obtained in analogy welding and real deep penetration laser welding are similar, which indicates that studying keyhole formation and the maintenance principle using the analogy welding method proposed in this paper may be helpful for deep understanding of the keyhole formation and maintenance mechanisms in real deep penetration laser welding. [ABSTRACT FROM AUTHOR]

The effects of gas flow rate and 22 kinds of nozzle layouts on the circulation flow rate were researched during the RH refining process using a water model and a mathematical model. Numerical simulations agreed with the water model experiment well. The results showed that the circulating flow rate increased with an increase of the gas flow rate. The critical value of the gas flow rate was 2.4 m3/h. Out of the 22 kinds of layouts, the 127-87 symmetrical layout was the optimal layout, for which the circulating flow rate reached 29.8 m3/h, the area of blind zone was the smallest and the mixing effect of the molten steel was the best. The working stroke and carrying capacity of the bubbles were important factors that affected the circulating flow rate. Among the four types of layouts, when the nozzles were in the one-side layout and the one-row layout, the main factor for improving the circulating flow rate was the working stroke of the bubbles. When nozzles were in the staggered layout and the symmetrical layout, the carrying capacity of the bubbles was the main factor for improving the circulating flow rate. For the same conditions, the carrying capacity of the bubbles had a greater effect on improving the circulating flow rate than the bubble stroke. [ABSTRACT FROM AUTHOR]

Differential Scanning Calorimetry (DSC) is a regular and powerful tool to measure the specific heat profile of various materials. Hydrogen bonds play a crucial role in stabilizing the three-dimensional structure of proteins. Naturally, information about the strength of hydrogen bonds is contained in the measured DSC profiles. Despite its obvious importance, there is no approach that would allow the extraction of such information from the heat capacity measurements. In order to connect the measured profile to microscopic properties of a polypeptide chain, a proper model is required to fit. Using recent advances in the Zimm–Bragg (ZB) theory of protein folding in water, we propose a new and efficient algorithm to process the DSC experimental data and to extract the H-bonding energy among other relevant constants. Thus, for the randomly picked set of 33 proteins, we have found a quite narrow distribution of hydrogen bonding energies from 1 to 8 kJ/mol with the average energy of intra-protein hydrogen bonds h ¯ = 4. 2 ± 1. 5 kJ/mol and the average energy of water–protein bonds as h p s ¯ = 3. 8 ± 1. 5 kJ/mol. This is an important illustration of a tiny disbalance between the water–protein and intraprotein hydrogen bonds. Fitted values of the nucleation parameter σ belong to the range from 0.001 to 0.01, as expected. The reported method can be considered as complementary to the classical two-state approach and together with other parameters provides the protein–water and intraprotein H-bonding energies, not accessible within the two-state paradigm. [Display omitted] • The algorithm considers water effects in Zimm–Bragg model. • Extracts protein–water & intraprotein H-bond energies. • Improved fit over two-state model in DSC data analysis. • Challenges conventional cold denaturation predictions. • Complementary insights to traditional two-state approach. [ABSTRACT FROM AUTHOR]

Whereas approximately 96.3% of the steel produced worldwide is made by continuous casting, great emphasis is put on the superior efficiency of this process. The water model of the tundish and mathematical modeling is often used for the simulation of the steel flow during continuous casting. The experiments were performed on a model of the tundish with two outlets, at two casting speeds (0.8 m.s–1 and 1.2 m.s–1). Eight setups of the tundish were evaluated, which differed in the design of the dams (with or without drainage holes), in their distance from the center of the tundish, and their height. The contribution of the work is the analysis of phenomena in the tundish water model in conditions of repeatability (ten repetitions). The goal is to find the setup providing the most symmetrical flow, with the minimum difference in the residence times Δτ on the two outlets. Taking into account the results obtained at both casting speeds, the most preferred is setup 2 with the 87 mm high dams placed 587 mm from the center of tundish (Δτ = 0.5). The setup 3 (Δτ = 8.25) appears to be the least appropriate. The higher the casting speed, the higher the number of unsuitable arrangements.

The article presents the results of research aimed at determining the nature of changes in the mixing of liquid steel in asymmetrical tundish due to the increase in casting speed and the possibility of limiting the use of Flow Control Devices (FCD). The tests were carried out on the water model of the Continuous Steel Casting (CSC) device equipped with the tundish model. Four variants of casting speed were analyzed. The analysis of the obtained results was divided into two stages: qualitative analysis of flow and mixing (visualization process) and quantitative analysis of flow and mixing (by analysis of mixing curves - Residence Time Distribution (RTD) type F).

In this paper, by changing the shape of the inner wall of the nozzle, a water model experiment was carried out on the slab with the section of 200 / mm × 1 200 / mm. The results show that under the same immersion depth and the same angle, the improved No.1 nozzle and the improved No.2 nozzle have swirling flow, which reduced the dead region and the internal longitudinal flow velocity, and the swirl ratio generated in improved No. 2 nozzle is more obvious than improved No. 1 nozzle. The impact depth of the velocity at the outlet of the improved No.2 nozzle is obviously lower than that of the original nozzle and the improved No.1 nozzle. [ABSTRACT FROM AUTHOR]

A water model is built to investigate the transport phenomena in the slab continuous casting mold. The gas flow rate, casting speed, and slab width on the slag entrainment are studied. The sliver defect in the IF steel plate is analyzed by the scanning electron microscope. The slag entrainment is recorded by the high-speed camera and the velocity is measured by the PIV. The results show that sliver defects contain Al, Ca, Si, Mg, Na, and O, which are mainly derived from the mold slag entrainment. With the casting speed increase, the fluid velocity from the submerged entry nozzle rises clearly and the slag droplets detach from slag layer. As the gas flow rate increases, the liquid moves upward with bubble floating and attacks the slag-steel interface. It is suggested the gas flow rate should be less than 3.3 NL/min for the slab width of 1300 mm and the casting speed of 1.2 m/min. With the slab width increasing from 1300 mm to 1700 mm, no slag entrainment zone is reduced. The gas flow rate should be below 2.2 NL/min with the casting speed increasing to 1.4 m/min, both for the slab width of 1300 mm and 1700 mm. [ABSTRACT FROM AUTHOR]

Molecular self‐diffusion coefficients underlie various kinetic properties of the liquids involved in chemistry, physics, and pharmaceutics. In this study, 547 self‐diffusion coefficients are calculated based on all‐atom molecular dynamics (MD) simulations of 152 diverse pure liquids at various temperatures employing the OPLS4 force field. The calculated coefficients are compared with experimental data (424 extracted from the literature and 123 newly measured by pulsed‐field gradient nuclear magnetic resonance). The calculations well agree with the experimental values. The determination coefficient and root mean square error between the observed and calculated logarithmic self‐diffusion coefficients of the 547 entries are 0.931 and 0.213, respectively, demonstrating that the MD calculation can be an excellent industrial tool for predicting, for example, molecular transportation in liquids such as the diffusion of active ingredients in biological and pharmaceutical liquids. The self‐diffusion coefficients collected in this study are compiled into a database for broad researches including artificial intelligence calculations. [ABSTRACT FROM AUTHOR]

Among the two isoforms of amyloid-β i. e., Aβ-40 and Aβ-42, Aβ-42 is more toxic due to its increased aggregation propensity. The oligomerization pathways of amyloid-β may be investigated by studying its dimerization process at an atomic level. Intrinsically disordered proteins (IDPs) lack well-defined structures and are associated with numerous neurodegenerative disorders. Molecular dynamics simulations of these proteins are often limited by the choice of parameters due to inconsistencies in the empirically developed protein force fields and water models. To evaluate the accuracy of recently developed force fields for IDPs, we study the dimerization of full-length Aβ-42 in aqueous solution with three different combinations of AMBER force field parameters and water models such as ff14SB/TIP3P, ff19SB/OPC, and ff19SB/TIP3P using classical MD and Umbrella Sampling method. This work may be used as a benchmark to compare the performance of different force fields for the simulations of IDPs., (© 2024 Wiley-VCH GmbH.)

Numerous nanobiotechnologies include manipulations of short polypeptide chains. The conformational properties of these polypeptides are studied in vitro by circular dichroism and time-resolved infrared spectroscopy. To find out the interaction parameters, the measured temperature dependence of normalized helicity degree needs to be further processed by fitting to a model. Using recent advances in the Hamiltonian formulation of the classical Zimm and Bragg model, we explicitly include chain length and solvent effects in the theoretical description. The expression for the helicity degree we suggest successfully fits the experimental data and provides hydrogen bonding energies and nucleation parameter values within the standards in the field.

In order to solve the problem that the vulcanizing agent utilization rate is low and the dilution effect of copper slag is poor, the vortex stirring dilution method was used to improve the conditions of the dilution kinetics and copper recovery. The water model was used to simulate the effect of copper slag dilution. Under the premise of keeping the Reynolds number consistent, silicone oil and glass beads were used instead of copper slag and vulcanizing agent. Based on the relationship between voltage and concentration, the PC6D dual-channel particle concentration measuring instrument was used to study the stirring speed and the insertion depth of the stirring paddle in model experiments, and the suitable conditions were speed 250 rpm and insertion depth 70 mm. The fire dilution of copper slag was done under the conditions. After stirring and sedimentation, the Fe3O4 in slag decreased from 22.58% to 4.65%, and the copper content of the slag decreased from 2.94% to 0.34%. The copper recovery was 88.44%. [ABSTRACT FROM AUTHOR]

Tundish metallurgy is essential for continuous steel casting technology. In this study, the subflux flow controller (SFC) installed in the tundish pouring zone was tested, demonstrating the possibility of simultaneously reducing the dimensions of the flow control device (FCD) and effectively influencing the structure of the liquid steel flow. On the basis of computer simulations and water model trials, results were obtained describing the hydrodynamic structure in considered variants of the one strand slab tundish. Considering the influence of the SFC on the steel flow structure in the tundish, and the gradient of the wall shear stress and total pressure on the SFC surface/tundish walls, the most optimal SFC variant for a single-strand wedge-type tundish is SFC No. 2C. [ABSTRACT FROM AUTHOR]

In the continuous casting process, the fluid flow of molten steel in the tundish is in a non-isothermal state. Because of the geometric shape and process parameters of a multi-strand tundish, the fluid flow behavior of each strand is quite inhomogeneous, and the difference in temperature, composition and inclusion content between each strand is great, which directly affects the quality of the steel products. In this paper, the fluid flow, heat transfer phenomena and inclusion trajectories in a four-strand tundish with and without flow-control devices (FCDs) are investigated using a water model and numerical simulation in isothermal and non-isothermal conditions. The results show that natural convection has a significant influence on the flow pattern and temperature distributions of molten steel in the tundish. Without FCDs, the average residence times of the molten steel in the tundish obtained by the isothermal water model, non-isothermal water model and non-isothermal mathematical model were 251.2 s, 263.3 s and 266.0 s, respectively, and the dead zone volumes were 21.51%, 29.26% and 28.21%, respectively. With FCDs, the average residence times of the molten steel obtained by the isothermal water model, non-isothermal water model and non-isothermal mathematical model were 293.0 s, 304.0 s and 305.2 s, respectively, and the dead zone volumes were 43.98%, 50.23% and 52.78%, respectively. The flow characteristics of the molten steel in the tundish were different between the isothermal and non-isothermal conditions. Compared with isothermal conditions, the numerical simulation results were closer to the water model results in non-isothermal conditions. The trial results showed that the fluid flow in a tundish has a non-isothermal characteristic, and the results in non-isothermal conditions can better reflect the actual fluid flow and heat transfer behaviors of molten steel in a tundish. [ABSTRACT FROM AUTHOR]

The article presents the results of research aimed at determining the nature of changes in the mixing of liquid steel in asymmetrical tundish due to the increase in casting speed and the possibility of limiting the use of Flow Control Devices (FCD). The tests were carried out on the water model of the Continuous Steel Casting (CSC) device equipped with the tundish model. Four variants of casting speed were analyzed. The analysis of the obtained results was divided into two stages: qualitative analysis of flow and mixing (visualization process) and quantitative analysis of flow and mixing (by analysis of mixing curves - Residence Time Distribution (RTD) type F). [ABSTRACT FROM AUTHOR]

The behavior of molten steel stream in submerged entry nozzle (SEN) of the continuous casting machine affects nodulation inside the nozzle and stability of the nozzle outlet flow, etc., which directly affect the quality of the continuous casting billet. In this work, the effect of the SEN inner wall structure with addition of hemispherical crowns on the dynamic behavior of flow and the nozzle outlet velocity distribution was analyzed by means of water model experiments and numerical simulations. The overall results of this study show that after the hemispherical crowns are added to the nozzle inner wall, swirling flow is induced inside the nozzle, which reduces the dead region and the internal longitudinal flow velocity and accordingly reduces nodulation. Moreover, the nozzle outlet flow pattern is changed from a straight flow to a swirling flow, which significantly decreases the outlet flow velocity and thus reduces the impact on the steel shell in the mold. [ABSTRACT FROM AUTHOR]

Bath smelting and converting technologies for copper production have been improved, resulting in higher production efficiency and less polluting emissions. Reported studies on experimental and computational modeling approaches are reviewed in this paper, focusing on adjustable variables and flow details, for a thorough understanding of the complex flow phenomena of the high-temperature reactors used. Results from water models and Computational Fluid Dynamics (CFD) simulations indicate that the transport phenomena in different reactors should be analyzed separately, as flow behavior exhibits significant differences in different gas injecting regimes and furnace structures. Mixing behavior and further optimization for most furnaces are presented in this review, showing a considerable degree of agreement between experiments and computational simulations. In general, a deeper nozzle or tuyere level with a higher gas flow rate are factors in the majority of copper bath smelting and converting cases. However, the dynamic parameters cannot be infinitely increased, but should be maintained within an appropriate range to provide relatively high mixing efficiency while preventing refractory corrosion due to splashing. Research on detailed flow phenomena including bubbles and surface waves is relatively scarce. It is suggested that the most efficient reaction areas for furnaces in jetting and bubbling regimes are totally different, due to the differences in bubble behavior. Concerning the bath surface, the behavior of transversal standing waves and longitudinal waves has been preliminarily revealed using water models, suggesting that standing waves tend to disappear in particular ranges of bath height and gas flow rate. [ABSTRACT FROM AUTHOR]

Whereas approximately 96.3% of the steel produced worldwide is made by continuous casting, great emphasis is put on the superior efficiency of this process. the water model of the tundish and mathematical modeling is often used for the simulation of the steel flow during continuous casting. the experiments were performed on a model of the tundish with two outlets, at two casting speeds (0.8 m.s-1 and 1.2 m.s-1). eight setups of the tundish were evaluated, which differed in the design of the dams (with or without drainage holes), in their distance from the center of the tundish, and their height. the contribution of the work is the analysis of phenomena in the tundish water model in conditions of repeatability (ten repetitions). the goal is to find the setup providing the most symmetrical flow, with the minimum difference in the residence times Δτ on the two outlets. taking into account the results obtained at both casting speeds, the most preferred is setup 2 with the 87 mm high dams placed 587 mm from the center of tundish (Δτ = 0.5). The setup 3 (Δτ = 8.25) appears to be the least appropriate. the higher the casting speed, the higher the number of unsuitable arrangements. [ABSTRACT FROM AUTHOR]

The effect of top blowing and bottom blowing conditions on spitting behavior was investigated by water model experiments and numerical calculation. The results of the water model experiment showed that reducing the jet velocity by using a larger nozzle diameter was effective for reducing spitting. The numerical calculation indicated that interference between the top blown gas jet and the bottom blowing plume increases the gas velocity at the rim of the cavity, causing heavier spitting. A new index using the geometrical locations of the neighboring cavity and plume was proposed. The spitting rate decreased under conditions with lower interference by avoiding interaction between the top blown gas jet and the bottom blowing plume. The energy distribution in the blowing process was discussed based on a water model experiment using bath mixing time, bath vibration, and the spitting rate. The energy for spitting was explained convincingly by the difference between the energy input and the energy of bath vibration, cavity formation, and bath mixing. The results implied lower interference of the top and bottom gas resulted in lower energy for spitting generation. [ABSTRACT FROM AUTHOR]

Bottom-blowing copper smelting is a bath smelting technology recently developed in China. It has the advantages of good adaptability of raw materials, high oxygen utilization and thermal efficiency, and flexible production capacity. Plume eye is a unique phenomenon observed in the bottom-blowing copper-smelting furnace where the slag on the surface of the bath is pushed away by the high-pressure gas injected from the bottom. The existence of plume eye was first confirmed by analyzing the quenched industrial samples collected above the gas injection area and then investigated by laboratory water model experiments. Combining the plant operating data and the smelting mechanism of the copper concentrate, the role of the plume eye in bottom-blowing-enhanced smelting is analyzed. It reveals that the direct dissolution of copper concentrate as a low-grade matte into the molten matte can significantly accelerate the reactions between the concentrate and oxygen. The productivity of the bottom-blowing furnace is therefore increased as a result. The effects of the gas flow rate and thickness of the matte and of the slag layer on the diameter of the plume eye were studied using water-model experiments. It was found that increasing the gas flow and the thickness of the matte and reducing the thickness of the slag can increase the diameter of the plume eye. This work is of great significance for further understanding the copper bottom-blowing smelting technology and optimizing industrial operations.

Abstract The effect of top blowing and bottom blowing conditions on spitting behavior was investigated by water model experiments and numerical calculation. The results of the water model experiment showed that reducing the jet velocity by using a larger nozzle diameter was effective for reducing spitting. The numerical calculation indicated that interference between the top blown gas jet and the bottom blowing plume increases the gas velocity at the rim of the cavity, causing heavier spitting. A new index using the geometrical locations of the neighboring cavity and plume was proposed. The spitting rate decreased under conditions with lower interference by avoiding interaction between the top blown gas jet and the bottom blowing plume. The energy distribution in the blowing process was discussed based on a water model experiment using bath mixing time, bath vibration, and the spitting rate. The energy for spitting was explained convincingly by the difference between the energy input and the energy of bath vibration, cavity formation, and bath mixing. The results implied lower interference of the top and bottom gas resulted in lower energy for spitting generation.

A physical water model based on the similarity principle is established to investigate the fluid flow and mixing phenomena during the Ruhrstahl–Heraeus (RH) steel refining process. The velocity distribution and the turbulent features on the center section are obtained using particle image velocimetry (PIV) measurement. Two vortexes between the down‐leg snorkel and the ladle sidewall are observed. The effects of the number of gas‐injection nozzles and the liquid levels in the vacuum chamber on the fluid phenomena are performed. More injected nozzles and a higher liquid level in the vacuum chamber generate larger velocity in the ladle. Twenty monitors in the ladle are used to monitor the variation of the conductivity to obtain the mixing time, indicating that the mixing time varies much with locations. The distribution of the mixing time on the vertical center section of the ladle is obtained. Moreover, the relationship between the circulation rate and the mixing time is obtained, indicating that the mixing time decreases with increasing circulation rate, and the slope of their relationship is −0.35. [ABSTRACT FROM AUTHOR]

The improvement in mixing conditions in a vacuum refining unit plays an important role in enhancing the purity and decarburization of molten steel. Mixing time is an important index to evaluate the operation efficiency of a metallurgical reactor. However, in water models, the effect of salt tracer dosages on the measured mixing time in a vacuum reactor is not clear. In this study, a water model of a Single Snorkel Refining Furnace (SSRF) was established to study the effect of salt solution tracer dosages on the mixing time of monitor points. The experimental results show that, in some areas at the top of the ladle, the mixing time decreases first and then increases when increasing the tracer dosage. Numerical simulation results show that, when the tracer dosage increases, the tracer flows downwards at a higher pace from the vacuum chamber to the bottom of the ladle. This may compensate for the injection time interval of large dosage cases. However, the mass fraction of the KCl tracer at the right side of the bottom is the highest, which indicates that there may be a dead zone. For the dimensionless concentration time curves and a 99% mixing time, at the top of the vacuum chamber, the curve shifts to the right side and the mixing time decreases gradually with the increase in tracer dosage. At the bottom of the ladle, with the increase in tracer dosage, the peak value of the dimensionless concentration time curve is increased slightly. The mixing time of the bottom of the ladle decreases significantly with the increase in tracer dosage. However, in the dead zone, the mixing time will increase when the tracer dosage is large. At the top of the ladle, the effect of the tracer dosage is not obvious. The mixing time of the top of the ladle decreases first and then increases when increasing the tracer dosage. In addition, the mixing time of the top of the ladle is the shortest, which means that sampling at the top of the ladle in industrial production cannot represent the entire mixing state in the ladle.

The water transport through nanoporous multilayered graphene at 300k is investigated using molecular dynamics (MD) simulation with different water models in this study. We used functionalized and non-functionalized membranes along with five different 3-point rigid water models: SPC (simple point charge), SPC/E (extended simple point charge), TIP3P-FB (transferable intermolecular potential with 3 points—Force Balance), TIP3P-EW (transferable intermolecular potential with 3 points with Ewald summation) and OPC3 (3-point optimal point charge) water models. Based on our simulations with two water reservoirs and a porous multilayered graphene membrane in-between them, it is evident that the water transport varies significantly depending on the water model used, which is in good agreement with previous works. This study contributes to the selection of a water model for molecular dynamics simulations of water transport through multilayered porous graphene.

We use a density functional approach to calculate the contact angle of the water model on a heterogeneous, graphite-like surface. The surface heterogeneity results from the pre-adsorption of a layer of spherical species. The pre-adsorbed molecules can also be a mixture of molecules of different sizes. The presence of pre-adsorbed layer causes geometrical and energetical heterogeneity of the surfaces. Two cases are considered. The pre-adsorbed molecules can either behave like hard-sphere obstacles, or they can also attract the molecules of water. In the first case, an increase of the amount of pre-adsorbed species leads to an increase of the wetting temperature, but this increase does not depend linearly on the amount of obstacles. In the case of obstacles exerting attractive forces on water molecules, the curves describing the dependence between the amount of pre-adsorbed species and the contact angle can exhibit a maximum. In addition, we have also studied how the pre-adsorbed species influence the local densities of gaseous and liquid phases in contact with a modified solid surface.