scholarly journals Numerical Simulation of Macrosegregation with Solid Deformation During the Solidification of Steel Ingots Using a Single-Phase/Two-Phase Integrated Model

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 669
Author(s):  
Kangxin Chen ◽  
Houfa Shen
Keyword(s):  
Liquid Flow ◽  
Single Phase ◽  
Solid Phase ◽  
Steel Ingot ◽  
Integrated Model ◽  
Phase Model ◽  
Two Phase ◽  
Deformation Stage ◽  
Solid Deformation ◽  
Steel Ingots

Macrosegregation, a serious defect formed during the solidification of steel ingots, impairs the performance of the final components. To predict macrosegregation caused by thermal-solutal convection and solid deformation, a volume-averaged single-phase/two-phase integrated model is developed. During the deformation stage, the two-phase model coupling the solid deformation and liquid flow in the mushy zone is utilized. Before or after the deformation stage, the motion of the solid phase is neglected, and the single-phase model is solved. A 450 kg steel ingot punching test is considered for application. The results show that when the solid shell of the ingot is being punched, the solid phase in the mushy core at punching height is compressed, and a relative liquid flow is induced. This in turn causes a transition of positive segregation to negative segregation in the compressed mushy core of the ingot. According to numerical sensitivity tests of different punching parameters, as the punching start time and punching velocity increase, the effect of punching on macrosegregation will be smaller. It is demonstrated that the single-phase/two-phase integrated model can predict macrosegregation in the steel ingots which are deformed during solidification.

scholarly journals Influence of Blade Type on the Flow Structure of a Vortex Pump for Solid-Liquid Two-Phase Flow

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 353
Author(s):  
Hui Quan ◽  
Yanan Li ◽  
Lei Kang ◽  
Xinyang Yu ◽  
Kai Song ◽  
...  
Keyword(s):  
Flow Structure ◽  
Liquid Flow ◽  
Single Phase ◽  
Solid Phase ◽  
Internal Flow ◽  
Phase Flow ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Vortex Pump ◽  
Solid Liquid

Vortex pumps have good non-clogging performance owing to their impellers being retracted into retraction cavities, but they are much less efficient than ordinary centrifugal pumps. In this paper, numerical simulations were performed on a model of the 150WX200-20 vortex pump for four different blade types, and the influence of blade structure on pump performance was determined. The simulations revealed the existence of axial vortices in the flow passage between the blades in the impeller region. The geometric characteristics of these axial vortices were more regular in two-phase solid-liquid flow than single-phase liquid flow. The presence of the solid phase reduced the vortex strength compared with the single-phase flow and suppressed the increase in size of the secondary circulation vortex. It was found, however, that the blade shape had a greater influence on the circulating flow than the presence of the solid phase. The flow state of the medium flowing out of the impeller domain had a direct effect on the circulating flow with this effect being related to the law governing the flow of the medium in the flow channel between the blades. It was found that the performance of a front-bent blade was the best and that of a curved blade the worst. This influence of blade type on the internal flow structure was used to further explain the relationship between the internal flow structure and the external characteristics of the vortex pump, the understanding of which is crucial for blade selection and hydraulic optimization.

A quasi single-phase model for debris flows and its comparison with a two-phase model

2018 ◽  
Vol 15 (5) ◽  
pp. 1071-1089 ◽  
Author(s):  
Chun-chen Xia ◽  
Ji Li ◽  
Zhi-xian Cao ◽  
Qing-quan Liu ◽  
Kai-heng Hu
Keyword(s):  
Debris Flows ◽  
Single Phase ◽  
Phase Model ◽  
Two Phase

Two Phase Flow Patterns and Cooling Power of Mixed Refrigerant in Micro Cryogenic Coolers

2012 ◽  
Author(s):  
Ryan Lewis ◽  
Hayley Schneider ◽  
Yunda Wang ◽  
Ray Radebaugh ◽  
Y. C. Lee
Keyword(s):  
Liquid Flow ◽  
High Speed ◽  
Single Phase ◽  
Liquid Fraction ◽  
Cryogenic Cooling ◽  
Cooling Power ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Power Draw

Micro cryogenic coolers (MCCs) operating in the Joule-Thomson cycle with mixed refrigerants offer an attractive way to decrease the size, cost, and power draw required for cryogenic cooling. Recent studies of MCCs with mixed refrigerants have, when employing pre-cooling, shown pulsating flow-rates and oscillating temperatures, which have been linked to the refrigerant flow regime in the MCC. In this study we investigate those flow regimes. Using a high-speed camera and optical microscopy, it is found that the pulsations in flow correspond to an abrupt switch from single-phase vapor flow to single-phase liquid flow, followed by 2-phase flow in the form of bubbles, liquid slugs, and liquid slug-annular rings. After this period of 2-phase flow, the refrigerant transitions back to single-phase vapor flow for the cycle to repeat. Under different pre-cooling temperatures, the mole fraction of the vapor-phase refrigerant, as measured by molar flow-rate, agrees reasonably well with the quality of the refrigerant at that temperature as calculated by an equation of state. The frequency of pulsation increases with liquid fraction in the refrigerant, and the volume of liquid in each pulse only weakly increases with increasing liquid fraction. The cooling power of the liquid-flow is up to a factor of 7 greater than that of the 2-phase flows and single-phase vapor flow.

Hydrodynamics of gas-liquid flow in micropacked beds: Pressure drop, liquid holdup, and two-phase model

AIChE Journal ◽  
2017 ◽  
Vol 63 (10) ◽  
pp. 4694-4704 ◽  
Author(s):  
Jisong Zhang ◽  
Andrew R. Teixeira ◽  
Lars Thilo Kögl ◽  
Lu Yang ◽  
Klavs F. Jensen
Keyword(s):  
Pressure Drop ◽  
Liquid Flow ◽  
Phase Model ◽  
Liquid Holdup ◽  
Two Phase ◽  
Gas Liquid Flow

scholarly journals Effect of a Symmetric Contraction on the Concentration Profiles of a Particle-Laden Slurry

2011 ◽  
Author(s):  
A. Deshpande ◽  
K. Ramisetty ◽  
F. W. Chambers ◽  
M. E. McNally ◽  
R. M. Hoffman
Keyword(s):  
Single Phase ◽  
Solid Phase ◽  
Fluid Dynamic ◽  
Density Ratio ◽  
Primary Phase ◽  
Solid Particles ◽  
Concentration Profiles ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Slurry Concentration

In-line measurements and sample stream withdrawals for on-line and/or at-line measurements of slurries flowing in horizontal pipes can be complicated by nonuniform slurry profiles. More uniform profiles would improve measurements. Area contractions are a common means used to produce more uniform velocity fields for single phase flows. For example, contractions are used to condition the flow entering wind tunnel test sections and make velocity profiles more uniform at venturi throats. It was desired to determine whether area contractions could be used to make slurry concentration profiles more uniform in horizontal pipe flows. An ASME flow nozzle with a contraction diameter ratio of 0.5 was chosen as a well defined geometry to consider in a Computational Fluid Dynamic (CFD) study of the effects of a contraction on slurry concentration profiles. The pipe was 2.8 m long with a 50.8 mm diameter. The entrance of the contraction was placed at 35 pipe diameters from the inlet in fully developed flow. A length of 20 diameters followed the contraction. The slurry had a xylene liquid phase and an ADP solid phase with a density ratio of 1.7. The simulations were performed at primary phase velocities of 2 m/s and 4 m/s, corresponding to Reynolds numbers of 1.4E05 and 2.8E05. Spherical particle diameters of 38, 75, and 150 μm were used at concentrations of 0.05, 0.2, and 0.3. ANSYS FLUENT 12 software was used with the standard k-ε turbulence model and standard wall function. The mixture multi-phase model was used for the two-phase flow. An unstructured tetrahedral meshing scheme was used with 1.4 million elements. The grid was adjusted until the condition 30 < y+ <60 for the mesh point nearest the wall was satisfied. A grid refinement study was performed to insure grid independence. The computational scheme first was validated by comparing pipe flow velocity and concentration profiles to results in the literature. The computations performed with the contraction showed that in all cases the concentration profiles of the solid particles displayed greater uniformity than the profiles in the pipe upstream of the contraction. The effect of the contraction was more pronounced for the larger particles. As in the case of single phase flows, the contraction caused the axial turbulence intensity to decrease. The greater uniformity of the concentration profiles at the exit plane of the nozzle, suggest that the contraction can provide better conditions for performing measurements of a particle-laden slurry.

A Two-Phase Boundary Layer and Its Drag-Reduction Characteristics

1962 ◽  
Vol 29 (2) ◽  
pp. 408-414 ◽  
Author(s):  
E. M. Sparrow ◽  
V. K. Jonsson ◽  
E. R. G. Eckert
Keyword(s):  
Boundary Layer ◽  
Phase Boundary ◽  
Liquid Flow ◽  
Single Phase ◽  
Free Stream ◽  
Stream Velocity ◽  
Two Phase ◽  
Drag Forces ◽  
Liquid Boundary ◽  
Reduction Characteristics

Consideration is given to coexisting gas and liquid boundary layers which occur when a gas is injected at the surface of a flat plate into a free-stream liquid flow. It is postulated that the gas forms a continuous film over the plate surface. The problem can be formulated exactly within the framework of laminar boundary-layer theory. Solutions have been carried out for a range of values of blowing velocity and of a fluid property parameter (ρμ) L / (ρμ)g. It is demonstrated that the drag forces associated with the two-phase boundary layer are much smaller than those for the single-phase liquid flow. For example, for a blowing velocity which is 0.001 of the free-stream velocity and a gas Reynolds number of 105, the over-all drag calculation yields a value which is 0.0205 of the single-phase drag force. The effect of evaporation at the gas-liquid interface is analyzed and found to be small at temperatures which are not too close to saturation.

scholarly journals The Continuum Approach to the Description of Semi-Crystalline Polymers Deformation Regimes: The Role of Dynamic and Translational Defects

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1155 ◽  
Author(s):  
Yurii Grinyaev ◽  
Nadezhda Chertova ◽  
Evgeny Shilko ◽  
Sergey Psakhie
Keyword(s):  
Euclidean Space ◽  
Solid Phase ◽  
Dimensional Space ◽  
Amorphous State ◽  
Maxwell Model ◽  
Phase Model ◽  
Plastic Behavior ◽  
Two Phase ◽  
Crystalline Polymers ◽  
The Continuum

This paper presents a new approach to describe the mechanical behavior of semi-crystalline polymers, the plastic deformation of which is determined by their two-phase structure. To describe the plastic behavior of semi-crystalline polymers, a two-phase model is used. In the framework of this model, one phase is in a hard (crystalline) state, and the other in a soft (amorphous) state. The two-phase material is modeled by a single-phase homogeneous continuum based on the approximation of the effective medium. It is assumed that two infinitely close material points of the continuum are connected in series by elastic and viscous bonds, which corresponds to the Maxwell model. It is shown that, in this case, the Maxwell continuum is a pseudo-Euclidean space. Generalizing the definition of defects from a three-dimensional space to a four-dimensional pseudo-Euclidean space, we obtained a dynamic system of nonlinear, interrelated equations to describe the behavior of translational-type defects in the solid phase and dynamic defects in the amorphous phase. As an example of an application for these equations, the phenomenon of creep under uniaxial loading is considered. It is shown that the formalism of the proposed two-phase model makes it possible to describe creep phenomenon regularities, which correspond to both the aging theory and the flow theory.

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