scholarly journals A New Approach to Calculate the Velocity of Interdendritic Fluid Flow during Solidification Using Etched Surface Height of Actual Metal Ingot

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 927
Author(s):  
Zibing Hou ◽  
Zhiqiang Peng ◽  
Qian Liu ◽  
Zhongao Guo ◽  
Hongbiao Dong
Keyword(s):  
Fluid Flow ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Bearing Steel ◽  
New Approach ◽  
Velocity Magnitude ◽  
Interdendritic Fluid Flow ◽  
Gcr15 Bearing Steel ◽  
Etched Surface ◽  
Calculated Velocity

Macrosegregation remains one of main defects affecting metal materials properties, which is mainly caused by interdendritic fluid flow during solidifying. However, as for controlling actual specific segregation, it is still difficult to effectively measure or simulate this kind flow instead of pure fluid flow, especially in complex casting processes of high-grade materials. Herein, a new method for obtaining velocity magnitude and direction of interdendritic fluid flow during metal solidifying is proposed from boundary layer and standard deviation obtained by measuring etched surface heights of the actual ingot and using statistical principles. Taking continuous casting bloom of GCr15 bearing steel as an example, it is indicated that the calculated velocity magnitudes under different sides and superheats can be explained by process features and, hence, solidification mechanism. The velocity magnitude and fluctuation are higher on the inner curve side and under low superheat. Meanwhile, it is found that the fluctuation extent of secondary arm spacing is more relevant with interdendritic fluid flow, although its magnitude is mainly determined by the cooling rate. Moreover, on the basis of the calculated velocity directions and magnitudes, there is a positive correlation between segregation area ratio and the effective ratio between interdendritic flow velocity and growth velocity especially in the equiaxed grain zone, which corresponds with classic macrosegregation formation theory. The above findings and comparison with other results demonstrate the validity of the new approach, which can obtain the magnitude and the direction of interdendritic fluid velocity for two or three-dimensional multiscale velocity distribution by tailoring measuring length and numbers.

IMPORTANCE OF 3D VEHICLE HEAT EXCHANGER MODELING

2021 ◽  
pp. 1-10
Author(s):  
Michal Schmid ◽  
Fatih Bozkurt ◽  
Petr Pašcenko ◽  
Pavel Petržela
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Fluid Velocity ◽  
Coolant Temperature ◽  
Inlet Temperature ◽  
Vehicle Simulation ◽  
Velocity Magnitude ◽  
Primary Fluid ◽  
The Difference ◽  
Inlet Conditions

Abstract The work demonstrates, via a comprehensive study, the necessity of using a 3D CFD approach for heat exchanger (HTX) modelling within underhood vehicle simulation. The results are presented as the difference between 1D and 3D CFD approaches with a focus on auxiliary fluid (e.g. coolant) temperature prediction as a function of primary fluid (e.g. air) inlet conditions. It has been shown that the 1D approach could significantly underpredict auxiliary fluid inlet temperature due to neglecting the spatial distribution of primary fluid velocity magnitude. The resultant difference in the auxiliary fluid flow HTX inlet temperature is presented and discussed as a function of the Uniformity Index (UI) of the primary fluid flow velocity magnitude. Additionally, the 3D HTX model's importance is demonstrated in an industrial example of full 3D underhood simulation.

scholarly journals A CONCEPTUAL STUDY OF A LIQUID METAL ALLOY IN A DISK-SHAPED MAGNETOHYDRODYNAMICS CONVERSION SYSTEM

2021 ◽  
Vol 61 (2) ◽  
pp. 324-335
Author(s):  
Ayokunle O. Ayeleso ◽  
Atanda K. Raji
Keyword(s):  
Numerical Analysis ◽  
Liquid Metal ◽  
Current Density ◽  
Fluid Velocity ◽  
Fluid Pressure ◽  
Three Dimensional ◽  
Direct Conversion ◽  
Flow Stability ◽  
Mhd Generator ◽  
Velocity Magnitude

The use of solar-heated liquid metal in a magnetohydrodynamics (MHD) generator provides an alternative and direct conversion method for electric power generation. This prompted the present study to conduct a three-dimensional numerical analysis for a liquid Ga68In20Sn12 flow exposed to several uniform magnetic field intensities (Bo of 0.5 T, 1T and, 1.41 T) within a disk channel geometric boundary. The aim is to study the influence of the external magnetic fields on the generator performance and the fluid flow stability at a high Reynolds number (Re) and Hartmann number (Ha) using the Ansys Fluent software. The simulation results show that at Re of ≈ 2.44e6, the fluid velocity decreases inside the generator regardless of Bo. When Bo of 1T and 1.41T are applied, the velocity magnitude decreases and spreads within the disk channel and walls due to high Ha values (5874 and 8282). The fluid pressure increases from the nozzle pipe inlet to the disk channel and decreases towards the outlet. The induced current density in the radial direction, jx, increases within the disk channel and near the inner electrode edge as Bo increases. A significant observation is that the current densities obtained for Bo of 1T and 1.41T cases are higher than in other cases. The numerical analysis obtained in this study showed that the Bo of either 1T or 1.41T is needed to achieve the required flow stability, current density, and output powers.

SPH-Based Numerical Modeling of Fluid Flow Interaction with Various Shapes of Breakwater

2019 ◽  
Author(s):  
Rezaldy Naufal Saleh ◽  
Dede Tarwidi ◽  
Jondri
Keyword(s):  
Numerical Modeling ◽  
Fluid Flow ◽  
Coastal Erosion ◽  
Fluid Velocity ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Sph Method ◽  
Flow Interaction ◽  
Scale Down

Various efforts have been made to prevent coastal erosion. One of the efforts to prevent coastal erosion is to build breakwaters. This paper presents numerical modeling of fluid flow interaction with various shapes of breakwater. Fluid flow impact on different shapes of breakwater, i.e. trapezoidal prism, cylinder, and sphere has been investigated. The three-dimensional numerical modeling is purposed to decisive which breakwaters shape that can reduce the fluid velocity rapidly, compared to other tested breakwaters shapes. In this study, fluid motion is generated by dam break scheme. The fluid motion is governed by momentum and continuity equation. The equations of fluid motion are resolved by smoothed particle hydrodynamics (SPH) method. DualSPHysics, an open-source code based on SPH method, is applied to simulate fluid motion and the interaction with the blocks of breakwater. According to numerical results, the trapezoidal prism shape of breakwater can scale down the fluid velocity faster than the cylinder and sphere shape of breakwater with maximum velocity is about 2.20 m/s. Further, the cylinder shape yields the highest fluid velocity around the breakwater. The trapezoidal prism shape can be used as an effective breakwater.

Comparison of Two-Dimensional and Three-Dimensional Carbon Electrode Geometries Affecting Bidirectional Electroosmotic Pumping

2019 ◽  
Vol 7 (2) ◽  
Author(s):  
Matías Vázquez-Piñón ◽  
Hyundoo Hwang ◽  
Marc J. Madou ◽  
Lawrence Kulinsky ◽  
Sergio O. Martínez-Chapa
Keyword(s):  
Flow Behavior ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Electrode System ◽  
Flow Reversal ◽  
Peak Voltage ◽  
Velocity Magnitude ◽  
Electroosmotic Pumping ◽  
Coplanar Electrodes ◽  
Asymmetric Electrodes

This study compares fluid velocity magnitude and direction for three different glassy carbon (GC) electrode systems effecting alternating current (AC) electroosmotic pumping. The flow behavior is analyzed for electroosmotic pumping performed with asymmetric coplanar electrodes. Subsequently, effects of adding microposts array of two different heights (40 μm and 80 μm) are studied. Experimental results demonstrate that as peak-to-peak voltage is increased above 10 V peak-to-peak, the flow reversal is achieved for planar electrodes. Utilization of microposts-enhanced asymmetric electrodes blocks the flow reversal and alters the magnitude of the fluid velocity at the application of larger voltages (above 10 V peak-to-peak). Understanding of the consequences of three-dimensional geometry of asymmetric electrodes would allow designing the electrode system for AC electroosmotic pumping and mixing, as well as bidirectional fluid driving with equal forward and backward flow velocities.

scholarly journals Three-Dimensional Cellular Automata Simulation of the Austenitizing Process in GCr15 Bearing Steel

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3022
Author(s):  
Fuyong Su ◽  
Wenli Liu ◽  
Zhi Wen
Keyword(s):  
Cellular Automaton ◽  
Grain Growth ◽  
Three Dimensional ◽  
Bearing Steel ◽  
Cellular Automaton Model ◽  
Gcr15 Steel ◽  
Processing Times ◽  
Gcr15 Bearing Steel ◽  
Different Temperatures ◽  
Simulation Results

On the basis of the two-dimensional cellular automaton model, a three-dimensional cellular automaton model of austenitizing process was established. By considering the orientation of pearlite layer and the direction of austenite grain growth, the velocity of the interface was calculated during the austenitizing process. The austenitizing process of GCr15 steel was simulated, and the anisotropy of grain growth rate during austenitization was demonstrated by simulation results. By comparing the simulation results with the experimental data, it was found that the calculated results of the three-dimensional cellular automaton model established in this paper were in good agreement with the experimental results. By using this model, the three-dimensional austenitizing process of GCr15 steel at different temperatures and under different processing times can be analyzed, and the degree of austenitization can be predicted.

scholarly journals Diffusive instabilities and spatial patterning from the coupling of reaction–diffusion processes with Stokes flow in complex domains

2019 ◽  
Vol 877 ◽  
pp. 759-823 ◽  
Author(s):  
Robert A. Van Gorder ◽  
Hyunyeon Kim ◽  
Andrew L. Krause
Keyword(s):  
Fluid Flow ◽  
Pattern Formation ◽  
Cross Sections ◽  
Diffusion Processes ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Reaction Diffusion ◽  
Turing Instability ◽  
Reaction Diffusion Systems ◽  
Spatio Temporal

We study spatial and spatio-temporal pattern formation emergent from reaction–diffusion–advection systems formed by considering reaction–diffusion systems coupled to prescribed fluid flows. While there have been a number of studies on the planar dynamics of such systems and the resulting instabilities and spatio-temporal patterning in the plane, less has been done on complicated flows in complex domains. We consider a general approach for the study of bounded domains in order to model two- and three-dimensional geometries which are more likely to be of relevance for modelling dynamics within fluid vessels used in experiments. Considering a variety of problem geometries with finite cross-sections, such as two-dimensional channels, three-dimensional ducts and three-dimensional pipes, we demonstrate the role cross-section geometry plays in pattern formation under such systems. We find that the generic instability is that of an oscillatory or wave Turing instability, resulting in patterns which change in time, often being advected with the fluid flow. As in previous works, we observe a change in patterns formed when progressing from zero to weak to strong advection for uniform advection across the domain, with particularly strong advection destroying patterns. One novel finding is that heterogeneous fluid flow can induce qualitatively different patterns across the domain. For instance, Poiseuille flow with maximal advection in the centre of a vessel and zero advection at the boundary of a vessel is shown to exhibit patterns in the centre of the vessel which are different from patterns near the boundary, with differences attributed to the differential local advection within each region of the vessel. Additionally, we observe sheared patterns, which appear due to gradients in the fluid velocity, and cannot be obtained via any kind of uniform flow. Finally we also explore flow in more complex domains, including wavy-walled channels, continuous stirred-tank reactors, U-shaped pipes and a toroidal domain, in order to demonstrate behaviours when the flow is both heterogeneous and bidirectional, as well as to demonstrate that our results still apply for complex finite domains. Our analysis suggests that such non-trivial advection results in moving patterns which are more complex than observed in simpler reaction–diffusion–advection, and may be more characteristic of realistic flow regimes in biological media.

Influence of Large Turbo-Generator Stator Ventilation Ducts Structural Changes on Stator Temperature

2012 ◽  
Vol 462 ◽  
pp. 318-326
Author(s):  
Fei Yang Huo ◽  
Jia Hui Sun ◽  
Wei Li Li ◽  
Yi Huang Zhang
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Temperature Distribution ◽  
Velocity Distribution ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Flow And Heat Transfer ◽  
Turbo Generator ◽  
Ventilation Ducts ◽  
Cooling Air

For the complex status of fluid flow in stator radial ventilation ducts of large turbo-generator, the temperature distribution of stator is dramatically affected by the flow status of cooling medium in stator ventilating ducts. In this paper, a new ventilating ducts structure in stator is investigated. According to fixing a wind deflector on the stator teeth adjacent to the ventilation ducts, the fluid flow status of cooling air is changed flowing in stator ventilation ducts. For this reason, the effect of heat transfer in stator is changed. Taking an air-cooled turbo-generator as an example, considering the characteristics of fluid flow and heat transfer in turbo-generator ventilation system, the three-dimensional fluid flow and heat transfer coupling model is established. Using finite volume method, three-dimensional fluid field and temperature field control equations are coupling solved. Based on this, the velocity distribution in ventilating ducts is obtained. Besides that, the velocity distribution is studied with the cooling air flows into radial ventilation ducts at different incident angles. The influences of wind deflector and incident angles on the fluid velocity and temperature distribution are analyzed. Based on that, some useful conclusions are obtained.

Determination of Dynamic Drainage Volume in Water-Flood Operations Based on Fluid Flow Velocity Field Delineation

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Xiang Zhao ◽  
Qihao Qian ◽  
Chengfang Shi ◽  
John Yilin Wang
Keyword(s):  
Fluid Flow ◽  
Velocity Field ◽  
Flow Velocity ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
New Method ◽  
Drainage Volume ◽  
Flow Velocity Field ◽  
Fluid Flow Velocity ◽  
Effective Manner

Abstract Dynamic drainage volume is a useful measure in evaluating well completions, well spacing, and water-flood operations. It is usually approximated with a two-dimensional circle or a three-dimensional (3D) box that encloses a well using empirical correlations and production/injection volumes. While this approximation may be convenient, it certainly is not a good estimation for the effective and dynamic drainage volume, which is key for improved recovery. This paper proposes a new method to compute dynamic drainage volumes based on reservoir simulation results. A 3D fluid flow velocity field is first generated and then visualized as a function of time. Through velocity thresholding, one can delineate flow regions, and accurately and parsimoniously determine well drainage in water-flood operations. Our new method was proven to be more efficient and practical as demonstrated in a field-based synthetic model with nine injectors and 16 producers formed as an inverted five-spot water-flood pattern commonly used in the field, and a benchmark SPE 9 model. The novelty of the method lies in that a 3D fluid velocity field is generated to determine dynamic drainage volume. Our new method could be applied to optimize well placement and improve well operation, and finally increase the production in a heuristic, instructive, and cost-effective manner to maximize the estimated ultimate recovery.

Flow around a Triaxial Ellipsoid in a Long Circular Tube

2011 ◽  
Vol 66 (8-9) ◽  
pp. 481-488
Author(s):  
Doo-Sung Lee
Keyword(s):  
Differential Equation ◽  
Fluid Dynamics ◽  
Fluid Flow ◽  
Circular Cylinder ◽  
Circular Tube ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Triaxial Ellipsoid ◽  
Viscous Fluid Flow ◽  
Integro Differential Equation

Abstract This paper deals with the three-dimensional analysis of viscous fluid flow in a long circular cylinder containing an ellipsoidal obstacle. The center of the ellipsoid coincides with that of the cylinder, and the flow is confined to the space between the ellipsoid and the cylinder when the fluid velocity at the large distance from the ellipsoid is uniform. The equations of the classical theory of fluid dynamics are solved in terms of an unknown function which is then shown to be the solution of a boundary integro-differential equation. A numerical solution of the integro-differential equation is obtained and the pressure on the surface of the ellipsoid is presented in graphical forms for various values of the radius of the circular tube.

Silicon layers grown over SiO2 by liquid phase epitaxy: Electron Microscopical study

1990 ◽  
Vol 48 (4) ◽  
pp. 566-567
Author(s):  
F. Banhart ◽  
F.O. Phillipp ◽  
R. Bergmann ◽  
E. Czech ◽  
M. Konuma ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Phase ◽  
Plasma Etching ◽  
Liquid Phase Epitaxy ◽  
Three Dimensional ◽  
Microscopical Study ◽  
Sample Temperature ◽  
Structural Defects ◽  
Si Substrates ◽  
Etched Surface

Defect-free silicon layers grown on insulators (SOI) are an essential component for future three-dimensional integration of semiconductor devices. Liquid phase epitaxy (LPE) has proved to be a powerful technique to grow high quality SOI structures for devices and for basic physical research. Electron microscopy is indispensable for the development of the growth technique and reveals many interesting structural properties of these materials. Transmission and scanning electron microscopy can be applied to study growth mechanisms, structural defects, and the morphology of Si and SOI layers grown from metallic solutions of various compositions.The treatment of the Si substrates prior to the epitaxial growth described here is wet chemical etching and plasma etching with NF3 ions. At a sample temperature of 20°C the ion etched surface appeared rough (Fig. 1). Plasma etching at a sample temperature of −125°C, however, yields smooth and clean Si surfaces, and, in addition, high anisotropy (small side etching) and selectivity (low etch rate of SiO2) as shown in Fig. 2.

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