Macrosegregation Caused by Deformation of the Mushy Zone

2006 ◽  
Vol 508 ◽  
pp. 187-192 ◽  
Author(s):  
Lilia C. Nicolli ◽  
Christophe L. Martin ◽  
Asbjørn Mo ◽  
Olivier Ludwig
Keyword(s):  
Mushy Zone ◽  
Experimental Test ◽  
Continuum Model ◽  
Interdendritic Liquid ◽  
Outer Part ◽  
Selected Lines ◽  
Two Phase ◽  
Set Up ◽  
Future Work

An experimental set-up for investigating macrosegregation formation due to deformation of an isotropic metallic mushy zone is presented. In the experiment, a semisolid Al-5.9wt%Cu sample is isothermally and non-uniformly compressed. Concentration and eutectic fraction are measured along selected lines, after quenching the sample. Results show that interdendritic liquid is pressed out of the central part of the sample to its outer part, increasing the concentration in this region. The experimental test is then addressed by a two-phase continuum model recently presented elsewhere. The modelling results show the same tendencies observed experimentally, although local variations in composition are not well correlated. Suggestions for future work are made.

scholarly journals Endoscopic Pan/Tilt Camera for Thorax Interventions – Design and first results

2019 ◽  
Vol 5 (1) ◽  
pp. 517-519
Author(s):  
Alexander Mrokon ◽  
Peter P. Pott ◽  
Volker Steger
Keyword(s):  
Minimally Invasive ◽  
Inclination Angle ◽  
Magnetic Circuit ◽  
Mechanical Stability ◽  
Fem Simulation ◽  
Camera System ◽  
Design Changes ◽  
First Results ◽  
Set Up ◽  
Future Work

AbstractMinimally invasive surgery in some cases suffers from a limited view because certain areas are obscured by others. In this paper, a system is described, which can be used in minimally invasive procedures as an addition to a standard endoscope to improve the range of view. Through FEM simulation a magnetic circuit was designed to position the camera head. Subsequently, a camera positioning system was set up that includes an extracorporeal and an intracorporeal unit. The first controls the intracorporeal system. The latter has a camera inclination angle of up to 65° and an additional vertically downward viewing angle when aligned in parallel (inclination angle 0°). The panning angle is 360°. The camera system was evaluated in lab and cadaver trials. It has been found that the size of the intracorporeal system (16 × 10 × 150 mm) represents a major problem. Future work will focus of the reduction of the system’s size, the improvement of the camera image quality, and design changes considering mechanical stability.

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a ringlike wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions, namely, one with and one without this ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

Permeability in the Mushy Zone

2010 ◽  
Vol 649 ◽  
pp. 399-408 ◽  
Author(s):  
R.G. Erdmann ◽  
D.R. Poirier ◽  
A.G. Hendrick
Keyword(s):  
Mushy Zone ◽  
Volume Fraction ◽  
Primary Dendrite ◽  
Fluid Velocity ◽  
Interdendritic Liquid ◽  
Creeping Flow ◽  
Liquid Region ◽  
Local Volume ◽  
Local Volume Fraction ◽  
Deterministic Function

When modeled at macroscopic length scales, the complex dendritic network in the solid-plus-liquid region of a solidifying alloy (the “mushy zone”) has been modeled as a continuum based on the theory of porous media. The most important property of a porous medium is its permeability, which relates the macroscopic pressure gradient to the throughput of fluid flow. Knowledge of the permeability of the mushy zone as a function of the local volume-fraction of liquid and other morphological parameters is thus essential to successfully modeling the flow of interdendritic liquid during alloy solidification. In current continuum models, the permeability of the mushy zone is given as a deterministic function of (1) the local volume fraction of liquid and (2) a characteristic length scale such as the primary dendrite arm spacing or the reciprocal of the specific surface area of the solid-liquid interface. Here we first provide a broad overview of the experimental data, mesoscale numerical flow simulations, and resulting correlations for the deterministic permeability of both equiaxed and columnar mushy zones. A extended view of permeability in mushy zones which includes the stochastic nature of permeability is discussed. This viewpoint is the result of performing extensive numerical simulations of creeping flow through random microstructures. The permeabilities obtained from these simulations are random functions with spatial autocorrelation structures, and variations in the local permeability are shown to have dramatic effects on the flow patterns observed in such microstructures. Specifically, it is found that “lightning-like” patterns emerge in the fluid velocity and that the flows in such geometries are strongly sensitive to small variations in the solid structure. We conclude with a comparison of deterministic and stochastic permeabilities which suggests the importance of incorporating stochastic descriptions of the permeability of the mushy zone in solidification modeling.

Embedded Two-Phase Cooling of High Flux Electronics via Micro-Enabled Surfaces and Fluid Delivery Systems (FEEDS)

2015 ◽  
Author(s):  
Raphael Mandel ◽  
Serguei Dessiatoun ◽  
Patrick McCluskey ◽  
Michael Ohadi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Saturation Temperature ◽  
Absolute Pressure ◽  
High Flux ◽  
Vapor Quality ◽  
Two Phase ◽  
Fluid Delivery ◽  
Future Work

This work presents the experimental design and testing of a two-phase, embedded manifold-microchannel cooler for cooling of high flux electronics. The ultimate goal of this work is to achieve 0.025 cm2-K/W thermal resistance at 1 kW/cm2 heat flux and evaporator exit vapor qualities at or exceeding 90% at less than 10% absolute pressure drop. While the ultimate goal is to obtain a working two-phase embedded cooler, the system was first tested in single-phase mode to validate system performance via comparison of experimentally measured heat transfer coefficient and pressure drop to the values predicted by CFD simulations. Upon validation, the system was tested in two phase mode using R245fa at 30°C saturation temperature and achieved in excess of 1 kW/cm2 heat flux at 45% vapor quality. Future work will focus on increasing the exit vapor quality as well as use of SiC for the heat transfer surface upon completion of current experiments with Si.

On one-dimensional unsteady flow at infinite Mach number

1968 ◽  
Vol 304 (1478) ◽  
pp. 255-273 ◽  
Keyword(s):  
Asymptotic Expansion ◽  
Blast Wave ◽  
Outer Part ◽  
The Body ◽  
Viscous Boundary Layer ◽  
Outer Flow ◽  
Hypersonic Speeds ◽  
Set Up ◽  
Viscous Boundary ◽  
Infinite Set

The use of the blast-wave analogy, as an aid to the interpretation of experimental data on the motion of a fluid past an obstacle at hypersonic speeds, has led to the theoretical study of its role in an asymptotic expansion of the solution to the governing equations at large distances downstream of the body. In all attempts to set up such an expansion it has proved necessary to divide the flow régime into two parts, an outer part dominated by the blast wave and an inner part consisting of streamlines which, originally, pass close by the body. The matching of these two regions is apparently only possible if a certain integral vanishes. In the present paper a numerical integration, in one particular set of circumstances, is carried out to test the validity of the asymptotic expansion proposed. Formally, an unsteady problem is tackled, for ease of computation, but the steady analogue follows immediately and is of exactly the form discussed in the earlier investigations. It is found that the main results are in line with the theory and that the integral in question is indistinguishable from zero. However, a deeper investigation of the asymptotic expansion shows that, for an expansion of the type envisaged, an infinite set of integrals must each vanish. The next integral does not appear to be zero according to our computations but this result is not believed to be conclusive. Assuming that all the integrals do vanish, then it appears that the inner layer, which although inviscid, has many of the characteristics of a viscous boundary layer, has the addi­tional, surprising property that it can exert no direct influence on the outer flow at large distances downstream of the body.

scholarly journals Two Phase Separation using Liquid Level Control System using PLC and SCADA

2019 ◽  
Vol 9 (2) ◽  
pp. 2389-2391
Keyword(s):  
Supervisory Control ◽  
Programmable Logic ◽  
Level Control ◽  
Fluid Level ◽  
Two Phase ◽  
Two Fluids ◽  
Control Framework ◽  
Set Up ◽  
The Individual ◽  
Fluid Levels

Activity of the plant requires a great deal of work and human asset and requires a ton of diligent work and persistence as the individual needs to take note of every single an incentive at various occasions by taking readings physically. With the advancement of Industrial Automation, fluid level control framework has been generally utilized in different fields. In this paper, in light of PLC a control framework is set up by PID calculation and this control framework can alter two diverse fluid levels consequently. On the off chance that there are two distinct kinds of fluids with various densities in an equivalent tank and so as to isolate those two fluids, Level control framework dependent on SCADA and PLC is actualized. This framework satisfies splendidly the need of various fluid level control framework in industry, and it brings advantageous and exact for controlling. The proposed framework gives the fluid Level control, with the assistance of Programmable Logic Controllesr (PLCs), and Supervisory Control and Data Acquisition (SCADA).

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a Ring-like wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions — namely, one with and one without this Ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back-flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

A Continuum Damage Model for Functionalized Graphene Membranes Based on Atomistic Simulations

2017 ◽  
Vol 754 ◽  
pp. 173-176
Author(s):  
Ivano Benedetti ◽  
R.A. Soler-Crespo ◽  
A. Pedivellano ◽  
Wei Gao ◽  
H.D. Espinosa
Keyword(s):  
Continuum Model ◽  
Damage Model ◽  
Atomistic Simulations ◽  
Band Model ◽  
Continuum Damage ◽  
Two Phase ◽  
Elastic Continuum ◽  
Continuum Damage Model ◽  
Crack Band ◽  
Hyper Elastic

A continuum model for GO membranes is developed in this study. The model is built representing the membrane as a two-dimensional, heterogeneous, two-phase continuum and the constitutive behavior of each phase (graphitic or oxidized) is built based on DFTB simulations of representative patches. A hyper-elastic continuum model is employed for the graphene areas, while a continuum damage model is more adequate for representing the behavior of oxidized regions. A finite element implementation for GO membranes subjected to degradation and failure is then implemented and, to avoid localization instabilities and spurious mesh sensitivity, a simple crack band model is adopted. The developed implementation is then used to investigate the existence of GO nano-representative volume elements.

Experimental Research on Drag Torque for Single-plate Wet Clutch

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Hu Jibin ◽  
Peng Zengxiong ◽  
Wei Chao
Keyword(s):  
Contact Angle ◽  
Surface Tension Force ◽  
Transmission Efficiency ◽  
Viscous Drag ◽  
Drag Torque ◽  
Two Phase ◽  
Rotating Speed ◽  
Single Plate ◽  
Wet Clutch ◽  
Set Up

The relative motion between the friction and separate plates in a disengaged wet clutch causes viscous drag torque when the lubrication fluid flows through the clearance. Reduction of the drag torque is one of the important potentials for the improvement of transmission efficiency. The objective of this study is to set up an experimental rig to measure drag torque for a single-plate wet clutch. Visualization of the flow pattern in the clearance through transparent quartz was presented. Design factors and lubrication conditions were tested to evaluate the effects on drag torque. A comparison between the nongrooved plate and grooved plate was made. Plates made up of different materials were also tested to reveal the effects caused by the contact angle. Drag torque increases linearly at low rotating speeds and gradually decreases at high rotating speeds. It is confirmed that fluid completely covers the plate surface at a low rotating speed and air mixes with the fluid at a high rotating speed. A low feeding flow rate is useful to reduce drag torque. The reduction of the drag torque benefits from radial and deep grooves compared to a flat plate. A small contact angle near the stationary plate plays an important role in maintaining the oil film, however, it has little effect on the drag torque at the rotating side because the hydrodynamic force becomes dominant compared to the surface tension force. The test results help to build an accurate mathematical model based on two-phase flow lubrication.

Sign in / Sign up

Export Citation Format

Share Document