Phase Flow Analysis Research Articles

Two phase flow analysis of micro channel evaporator to investigate effect of geometry on pressure and heat transfer coefficient with respect to volume of fraction

Abstract Pressure and heat transfer coefficient (HTC) are parameters used to measure the performance of microchannel evaporators (MCE). By keeping the same overall dimensions, optimised hydraulic diameters of three different port shapes, square, rectangle and trapezoid, are analysed using CFD software to study the effect of geometry on the performance characteristics of MCE. The number of square, rectangle, and trapezoid channels is 580, 986, and 812, respectively. CFD analysis of the evaporator using R134a refrigerant is performed using the Volume of Fluid (VOF) with the SST k-ω model and Lee model for interphase mass transfer trace. Variation of pressure and HTC concerning volume of fraction liquid refrigerant (α) is compared for these three port structures. The trapezoid port microchannel evaporator (MCE) exhibits the highest pressure drop compared to square and rectangular port MCEs. The rectangular port MCE demonstrates the highest heat transfer coefficient among the configurations studied. The rectangular port MCE outperforms both square and trapezoid port MCEs in overall performance.

Influence of permeability on rainfall infiltration based on water gas two phase flow

The permeability function is one of the key properties in unsaturated soil mechanics and variation of parameters in soil water characteristic curve can easily affect matric suction as well as infiltration. The purpose of this research is to explore the significant effect of parameters in SWCC on rainfall infiltration. A water gas two phase flow analysis method was conducted to investigate the influence of parameters in SWCC on stable infiltration intensity. Result showed that when saturation was low, stable intensity of infiltration was greatly affected by matric suction because the modified parameters were related to pore size distribution such as air entry value ρ0 and parameter m. When saturation was close to 1, the influence of soil infiltration intensity was almost not affected by matric suction. The minimum value of stable infiltration of intensity was mainly determined by the intrinsic permeability, while saturation of this value was mainly affected by soil water characteristic curve, intrinsic permeability coefficient of soil as well as water relative permeability coefficient.

Pulmonary arterial banding in mice may be a suitable model for studies on ventricular mechanics in pediatric pulmonary arterial hypertension

BackgroundThe role of interventricular mechanics in pediatric pulmonary arterial hypertension (PAH) and its relation to right ventricular (RV) dysfunction has been largely overlooked. Here, we characterize the impact of maintained pressure overload in the RV–pulmonary artery (PA) axis on myocardial strain and left ventricular (LV) mechanics in pediatric PAH patients in comparison to a preclinical PA-banding (PAB) mouse model. We hypothesize that the PAB mouse model mimics important aspects of interventricular mechanics of pediatric PAH and may be beneficial as a surrogate model for some longitudinal and interventional studies not possible in children.MethodsBalanced steady-state free precession (bSSFP) cardiovascular magnetic resonance (CMR) images of 18 PAH and 17 healthy (control) pediatric subjects were retrospectively analyzed using CMR feature-tracking (FT) software to compute measurements of myocardial strain. Furthermore, myocardial tagged-CMR images were also analyzed for each subject using harmonic phase flow analysis to derive LV torsion rate. Within 48 h of CMR, PAH patients underwent right heart catheterization (RHC) for measurement of PA/RV pressures, and to compute RV end-systolic elastance (RV_Ees, a measure of load-independent contractility). Surgical PAB was performed on mice to induce RV pressure overload and myocardial remodeling. bSSFP-CMR, tagged CMR, and intra-cardiac catheterization were performed on 12 PAB and 9 control mice (Sham) 7 weeks after surgery with identical post-processing as in the aforementioned patient studies. RV_Ees was assessed via the single beat method.ResultsLV torsion rate was significantly reduced under hypertensive conditions in both PAB mice (p = 0.004) and pediatric PAH patients (p < 0.001). This decrease in LV torsion rate correlated significantly with a decrease in RV_Ees in PAB (r = 0.91, p = 0.05) and PAH subjects (r = 0.51, p = 0.04). In order to compare combined metrics of LV torsion rate and strain parameters principal component analysis (PCA) was used. PCA revealed grouping of PAH patients with PAB mice and control subjects with Sham mice. Similar to LV torsion rate, LV global peak circumferential, radial, and longitudinal strain were significantly (p < 0.05) reduced under hypertensive conditions in both PAB mice and children with PAH.ConclusionsThe PAB mouse model resembles PAH-associated myocardial mechanics and may provide a potential model to study mechanisms of RV/LV interdependency.

Prediction of particle size near-hole using with gas-liquid two phase flow analysis

Prediction of particle size near-hole using with gas-liquid two phase flow analysis

Flow Simulation in Abrasive Fluid Jet Machining with Water as Carrier Medium using CFD

Tremendous growth is seen in the field Machining of Materials where the engineering applications are highly demandable. Currently Abrasive Fluid Jet Machining is used to machine wide range of Engineering and Structural Materials including Aerospace, Defense and Aircraft Application which require high strength to weight and stiffness to weight ratios. In Abrasive fluid jet machining the abrasives are premixed with a suspended liquid to form slurry. The flow of the Abrasive Fluid mixture through the nozzle, results in rapid wear of the nozzle which degrades the cutting performance. This may lead to the divergence of the Abrasive Fluid Jet such that the angle of impingement varies. This jet impingement angles have more influence on the machining responses than the normal jet impingement angle as the depth of cut is improved thereby minimizing the shallow cuts within the same total cutting time. Nozzle replacement cost plays a vital role in the economics of the machining process and improvements in its wear characteristics are critical for the growth of such machining technology. It is well known that the inlet pressure of the abrasive fluid suspension has significant effect on the erosion characteristics of the inside surface in the nozzle. An analysis was carried out with constant nozzle taper angle and water as carrier medium. The objective of this work is to analyse the effect of inlet operating pressure on wall shear and exit kinetic energy with respect to Carrier medium. The two phase flow analysis was carried by using computational fluid dynamics tool CFX. The availability of optimized process parameters of abrasive fluid jet machining is limited to water and experimental test can be cost prohibitive. In this case computational fluid dynamics analysis provided better results.

On Image Processing Algorithm for Registration of Three-Dimensional Gas Bubble Movement Using a High Speed Camera

The paper deals with an imaging computer tomography method based on simple image processing techniques for two phase flow analysis. Moreover, it has been presented the algorithm of 3D bubble trajectory reconstruction using a single high speed camera and the system of mirrors. In the experiment a glass tank filled with distilled water was used. The nozzle through which the bubbles were generated was placed in the center of the tank bottom. Through the use of basic image processing and analysis techniques such as noise reduction, smoothing, edge detection and few algorithms like close contour filling, tracking single bubble etc. proposed in paper it became possible to draw out 3D trajectories for gas bubble paths in liquid. In the paper the measurement error of imaging computer tomography method has been estimated. The maximum measurement error recorded for this method was within the limits ±0,65 [mm] for a certain set of parameters like: resolution, mirror angle and deviation error of z axis from the 90o vertical line. Trajectories of subsequently departing bubbles were visualized in the form of figures.

On Image Processing Algorithm for Registration of Three-Dimensional Gas Bubble Movement Using a High Speed Camera

The paper deals with an imaging computer tomography method based on simple image processing techniques for two phase flow analysis. Moreover, it has been presented the algorithm of 3D bubble trajectory reconstruction using a single high speed camera and the system of mirrors. In the experiment a glass tank filled with distilled water was used. The nozzle through which the bubbles were generated was placed in the center of the tank bottom. Through the use of basic image processing and analysis techniques such as noise reduction, smoothing, edge detection and few algorithms like close contour filling, tracking single bubble etc. proposed in paper it became possible to draw out 3D trajectories for gas bubble paths in liquid. In the paper the measurement error of imaging computer tomography method has been estimated. The maximum measurement error recorded for this method was within the limits ±0,65 [mm] for a certain set of parameters like: resolution, mirror angle and deviation error of z axis from the 90o vertical line. Trajectories of subsequently departing bubbles were visualized in the form of figures.

Simulation of Two Phase Flow Dynamics in Flexible Riser Exit Geometries for Oil and Gas Applications

Four different riser pipe exit configurations were modelled and the flow across them analysed using STAR CCM+ CFD codes. The analysis was limited to exit configurations because of the length to diameter ratio of riser pipes and the limitations of CFD codes available. Two phase flow analysis of the flow through each of the exit configurations was attempted. The various parameters required for detailed study of the flow were computed. The maximum velocity within the pipe in a two phase flow were determined to 3.42 m/s for an 8 (eight) inch riser pipe. After thorough analysis of the two phase flow regime in each of the individual exit configurations, the third and the fourth exit configurations were seen to have flow properties that ensures easy flow within the production system as well as ensure lower computational cost. Convergence (Iterations), total pressure, static pressure, velocity and pressure drop were used as criteria matrix for selecting ideal riser exit geometry, and the third exit geometry was adjudged the ideal exit geometry of all the geometries. The flow in the third riser exit configuration was modelled as a two phase flow. From the results of the two phase flow analysis, it was concluded that the third riser configuration be used in industrial applications to ensure free flow of crude oil and gas from the oil well during oil production.

Computational Fluid Dynamic Simulation of Flow in Abrasive Water Jet Machining

Abrasive water jet cutting is one of the most recently developed non-traditional manufacturing technologies. In this machining, the abrasives are mixed with suspended liquid to form semi liquid mixture. The general nature of flow through the machining, results in fleeting wear of the nozzle which decrease the cutting performance. The inlet pressure of the abrasive water suspension has main effect on the major destruction characteristics of the inner surface of the nozzle. The aim of the project is to analyze the effect of inlet pressure on wall shear and exit kinetic energy. The analysis could be carried out by changing the taper angle of the nozzle, so as to obtain optimized process parameters for minimum nozzle wear. The two phase flow analysis would be carried by using computational fluid dynamics tool CFX. It is also used to analyze the flow characteristics of abrasive water jet machining on the inner surface of the nozzle. The availability of optimized process parameters of abrasive water jet machining (AWJM) is limited to water and experimental test can be cost prohibitive. In this case, Computational fluid dynamics analysis would provide better results.

Computational Fluid Dynamics Analysis of Nozzle in Abrasive Water Jet Machining

Abrasive water jet cutting is one of the most recently developed non-traditional manufacturing technologies. The general nature of flow through the machining, results in rapid wear of the nozzle which decrease the cutting performance. It is well known that the inlet pressure of the abrasive water suspension has main effect on the erosion characteristics of the inner surface of the nozzle. The objective of the project is to analyze the effect of inlet pressure on wall shear and exit kinetic energy. The analysis would be carried out by varying the inlet pressure of the nozzle, so as to obtain optimized process parameters for minimum nozzle wear. The two phase flow analysis would be carried by using computational fluid dynamics tool CFX. The availability of minimized process parameters such as of abrasive water jet machining (AWJM) is limited to water and experimental test can be cost prohibitive.

Underway analysis of nanomolar dissolved reactive phosphorus in oligotrophic seawater with automated on-line solid phase extraction and spectrophotometric system

The automated in-field determination of trace phosphate (and other nutrients) is highly valuable for studying nutrient dynamics and cycling in oligotrophic oceans. Here, we report an automated portable analyzer for week-long underway analysis of nanomolar dissolved reactive phosphorus (DRP) in seawater. The method is based on classic phosphomolybdenum blue (PMB) chemistry combined with on-line solid phase extraction (SPE) and flow analysis. Under optimized conditions, the formed PMB from sample is automatically concentrated on a hydrophilic lipophilic balanced (HLB) copolymer SPE. The PMB compound can be eluted with NaOH solution and measured in a flow-through detection system. All the components of the analyzer are computer controlled using laboratory-programmed software based on LabVIEW. The system exhibited advantages of high sensitivity (detection limit of 1.0 nmol L−1) and reproducibility (relative standard deviation of 5.4%, n = 180), insignificant carry-over effect and no interferences from salinity, silicate, arsenate and other P-containing compounds (concentrations at environmental level). The analytical time was 4–7 min/sample, depending on the DRP concentration. The accuracy of the method was validated through the analysis of reference materials and comparison with two other published methods (slope of 0.986 ± 0.027, intercept of 0.39 ± 0.64 nmol L−1, R2 of 0.9608, range of 0–80 nmol L−1, n = 57). The system has been successfully applied for a two-week continuous underway determination of DRP in surface seawater during a cruise in the South China Sea. Based on the laboratory and field evaluations, it is concluded that this system is suitable for accurate and high resolution underway DRP measurements in oligotrophic areas.

Cine viability magnetic resonance imaging of the heart without increased scan time

Cardiac magnetic resonance imaging (MRI) provides information about myocardial morphology, function, and viability from cine, tagged, and late gadolinium enhancement (LGE) images, respectively. While the cine and tagged images are acquired in a time-resolved fashion, the LGE images are acquired at a single timeframe. The purpose of this work is to develop a method for generating cine LGE images without additional scan time. The motion field is extracted from the tagged images, and is then used to guide the deformation of the infarcted region from the acquired LGE image at the acquired timeframe to any other timeframe. Major techniques for motion estimation, including harmonic phase (HARP) and optical flow analysis, are tested in this work for motion estimation. The proposed method is tested on numerical phantom and images from four human subjects. The generated cine LGE images showed both viability and wall motion information in the same set of images without additional scan time or image misregistration problems. The band-pass optical flow analysis resulted in the most accurate motion estimation compared to other methods, especially HARP, which fails to track points at the myocardial boundary. Infarct transmurality from the generated images showed good agreement with myocardial strain, and wall thickening showed good agreement with that measured from conventional cine images. In conclusion, the developed technique allows for generating cine LGE images that enable simultaneous display of wall motion and viability information. The generated images could be useful for estimating myocardial contractility reserve and for treatment prognosis.

Numerical simulation of adhesion of sea-salt particles on bridge girders

It is important to estimate corrosion environment of steel bridges for a proper corrosion prevention and maintenance program. The governing factors of corrosion are temperature, humidity and various dusts on the surfaces. Among them, the adhered sea-salt particulate matter (SSPM) is most important and therefore airborne SSPM near a bridge site must be considered in its design. To prevent degradation of protective paint, removal of adhered SSPM by wash out has been tried in some bridges. To this end, it is better to know the adhesion behaviour of SSPM to bridge girders. The objective of this manuscript is to pursue numerical method to simulate the adhesion behaviour of salt particles oriented from sea surface. Specifically, two scale approach is proposed. Mesoscale meteorological analysis and Lagrangian type two phase flow analysis are used in global and local analyses respectively. The comparisons between the numerical and observed results showed that the numerical analysis can reproduce essential behaviours of airborne SSPM.

A new approach to two-phase flow analysis in a rod bundle

This paper deals with the development of a mathematical and numerical technique for the steady-state subchannel analysis. In view of the importance of the drift-flux model (DFM) in two phase flow analysis, the conservation equations are based on this model. The conservation equations are expressed in terms of five field equations: mixture and momentum continuity; liquid energy equations; gas continuity; and radial cross flow equation for the adjacent subchannels. The numerical algorithm of the single-phase subchannel analysis used in the DIYANA code are extended for the present two phase flow subchannel analysis. The transfer of mass, momentum and energy between adjacent subchannels are split into diversion, turbulent mixing and void drift cross-flow components. The transfer of mass by turbulent mixing is assumed to occur in a volume-for-volume scheme reflecting experimental observations. The phenomenon of lateral vapor drift and turbulent mixing enhancement with flow regime are included in the model. In order to validate the prediction, the GE 3×3 rod bundle experiments with both uniform and non-uniform radial power distribution are used. Good agreement has been obtained between the present numerical prediction and the available experimental data. Simulation results showed that the turbulent mixing and void drift phenomena flatten the void fraction and equilibrium vapor quality profile in the rod bundle cross section. The mathematical formulation is considered to be a major step toward a more basic understanding of two-phase flow analysis in fuel rod bundles. Therefore, a fast, efficient and stable numerical technique is presented in this paper for thermal-hydraulic analysis of nuclear reactors.

J053043 安定化気泡関数有限要素法によるマイクロ化学チップ内Y字合流・分岐部における液液二相流解析

In this paper, results of liquid-liquid two phase flow analysis at Y-junction point in micro chemical chip is carried out based on stabilized bubble function finite element method. As the state equation, the Navier Stokes equation with CFS model is introduced, and VOF method is employed for two phase flow analysis. An estimation equation of width from bottom to interface in parallel flow is derived, and the solution is applied to set of boundary condition near Y-junction point for downstream side.

Numerical Modeling of Flow in a Horizontal Sand Filter

Problem statement: Horizontal sand filters may offer some advantage over vertical sand filters as they could be used for in-line treatment of wastewaters. Horizontal pipelines of tens and if not hundreds of meters length, filled with ordinary sand or permeable reactive media such as activated carbon or natural zeolite or iron filings, may be used to remove impurities from mine drainage waters, sewer and storm waters. Approach: However, in reality, in industrial-scale applications, the sand filled horizontal structures are almost always avoided due to the fact that water seeks out the path of least resistance. Once such a path is created, the vast majority of the water channels towards the least resistance zone and very small percentage of the water will go through the sand. Results: This study, applying numerical modeling using FLUENT software, which is based on the integral control volume approach, explores a number of geometries to identify a design that helps the inlet water to sweep the entire sand with the least channeling. The Navier Stokes equations for laminar and incompressible flow through porous media (i.e., the sand) including the viscous resistance were solved. Retention time of a fluid with properties similar to water, called tracer, were also estimated using Eulerian unsteady two phase flow analysis. Conclusion: The results of the models showed that the geometries involving a pipe with spiral protrusions or plate (baffles) inside, would be partially successful in drawing the water away from the channeling zone and moving it through the sand, however the geometry with the spiral protrusions uses much less power than the one with the baffles.

Computer Aided Simulation of the Rheology Forging Process for Aluminum Alloys and its Experimental Investigation

Rheology forming is a novel processing method of semi-solid processing, which is different from traditional mold forging and conventional casting process. The rheological behavior of metallic alloys containing both solid and liquid phases was investigated with the low and high solid fraction ranges. Its obvious advantages are easier to produce complex work pieces because of excellent forming ability, more flexible to shape, and more compact in the inner quality for its high pressure. This research paper presents the theory of the rheology forming process and the results of the finite element simulation of rheology forming for aluminum alloys. In this proposed theoretical models for the rheology forming process involve simultaneous calculations performed with solid phase deformation and the liquid phase flow analysis. To analyze the rheology process, the new flow stress curves of rheology aluminum alloys and the viscosity for the simulation of two-phase flow phenomena have been proposed with as a function of temperature.

Doppler global velocimetry for the analysis of combustor flows

The principle of Doppler global velocimetry (DGV) and a DGV system optimized for time averaged three-component velocity measurements is described in this paper. Furthermore, the design of the different components of the DGV-system as well as the manner of its operation is presented. The volumetric, time averaged, three-component velocity distribution was acquired in the isothermal flow of a low NOx, staged combustion chamber sector from Rolls-Royce Deutschland. The combustor was developed within the German public-funded Engine 3E program. On the basis of the collected data, the complex flow phenomena in the combustor could be analyzed in detail and supported by CFD calculations. A recently developed, pulsed Nd:YAG laser now enables planar, time-averaged, three-component DGV application in combusting flow fields. Measurements were carried out in a single-nozzle, kerosene combustion chamber model, operated under atmospheric pressure. The successful measurements demonstrated the capability of DGV as a new tool for combustion research. It was possible to separately measure the gas velocity and the velocity of the fuel droplets, a promising capability of DGV for two phase flow analysis.

Drift-flux parameters for upward gas flow in stagnant liquid.

The drift-flux model is widely used for gas-liquid two phase flow analysis, because it is applicable to various flow patterns and a wide range of void fractions. The drift- flux parameters for upwa...