scholarly journals Numerical Treatment of the Interface in Two Phase Flows Using a Compressible Framework in OpenFOAM: Demonstration on a High Velocity Droplet Impact Case

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 78
Author(s):  
Giovanni Tretola ◽  
Konstantina Vogiatzaki
Keyword(s):  
High Velocity ◽  
Fast Moving ◽  
Fuel Injection ◽  
Volume Fraction ◽  
Surface Tension Force ◽  
Considerable Effect ◽  
Mitigation Strategies ◽  
Two Phase ◽  
Droplet Shape ◽  
The Impact

The ability to accurately predict the dynamics of fast moving and deforming interfaces is of interest to a number of applications including ink printing, drug delivery and fuel injection. In the current work we present a new compressible framework within OpenFOAM which incorporates mitigation strategies for the well known issue of spurious currents. The framework incorporates the compressible algebraic Volume-of-Fluid (VoF) method with additional interfacial treatment techniques including volume fraction smoothing and sharpening (for the calculation of the interface geometries and surface tension force, respectively) as well as filtering of the capillary forces. The framework is tested against different benchmarks: A 2D stationary droplet, a high velocity impact droplet case (500 m/s impact velocity) against a dry substrate and, with the same impact conditions, against a liquid film. For the 2D static droplet case, our results are consistent with what is observed in the literature when these strategies are implemented within incompressible frameworks. For the high impact droplet cases we find that accounting for both compressibility and correct representation of the interface is very important in numerical simulations, since pressure waves develop and propagate within the droplet interacting with the interface. While the implemented strategies do not alter the dynamics of the impact and the droplet shape, they have a considerable effect on the lamella formation. Our numerical method, although currently implemented for droplet cases, can also be used for any fast moving interface with or without considering the impact on a surface.

Influence of the Ageing Temperature on the Selected Mechanical Properties of the Ti6Al7Nb Alloy

2015 ◽  
Vol 641 ◽  
pp. 120-123 ◽  
Author(s):  
Robert Dąbrowski ◽  
Janusz Krawczyk ◽  
Edyta Rożniata
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Volume Fraction ◽  
Heating Temperature ◽  
Ageing Temperature ◽  
Sample Length ◽  
Two Phase ◽  
Β Phase ◽  
Α Phase ◽  
The Impact

The results of investigations of the influence of the ageing temperature on the selected mechanical properties i.e. hardness, fracture toughness (examined by the linear elastic fracture mechanics - KIctest) and impact strength (KV) of two-phase Ti6Al7Nb alloy, are presented in the hereby paper. Investigations were performed in the ageing temperatures range: 450÷650°C of the alloy previously undercooled from the selected heating temperature (in two-phase range) - equal 970°C. The heating temperature was determined on the basis of the dilatometric curve of the alloy heating in the system ΔL = f ((T), where: ΔL – change of the sample length, T – temperature, which was then differentiated in the system: ΔL/ΔT = f (T). The dilatometer L78 R.I.T.A of the LINSEIS Company was used in the tests. Investigations of the alloy microstructure in the ageing temperatures range 450÷650°C were carried out by means of the light microscope Axiovert 200 MAT of the Carl Zeiss Company. It was found that nearly equiaxial grains of the primary α phase occur in the microstructure (of the volume fraction app. 30%) and that the volume fraction of the new lamellar α phase - formed from the supersaturated β phase - increases. With an increase of the alloy ageing temperature, in the mentioned above range, a small increase of its hardness from 305 to 324HV as well as a decrease of stress intensity factor KIcfrom 67.3 to 48.6 MPa x m1/2and impact strength (KV) from 40.2 to 31.3 J. The impact tests results were supplemented by the fractographic documentation. It was found, that the characteristic features of the fractures of impact test samples do not exhibit essential differences in dependence of the ageing temperature and material hardness. The fractographic investigations were performed by means of the scanning electron microscope NovaNanoSEM 450.

Buoyancy-Driven Convection from a Vertical Heated Plate Suspended Inside a Nanofluid-Filled Cooled Enclosure

2020 ◽  
Vol 9 (1) ◽  
pp. 56-65
Author(s):  
Massimo Corcione ◽  
Antonio Natale ◽  
Alessandro Quintino ◽  
Vincenzo Andrea Spena
Keyword(s):  
Volume Fraction ◽  
Solid Phase ◽  
Brownian Diffusion ◽  
Heated Plate ◽  
Nanoparticle Dispersion ◽  
Two Phase ◽  
Square Enclosure ◽  
Average Temperature ◽  
Buoyancy Driven Convection ◽  
The Impact

Buoyancy-driven convection from a heated vertical plate suspended inside a nanofluid-filled square enclosure cooled at the walls, is studied numerically using a two-phase model based on the double-diffusive approach. The study is conducted under the assumption that the Brownian diffusion and thermophoresis are the only slip mechanisms by which the solid phase can develop a significant relative velocity with respect to the liquid phase. The system of the governing equations of continuity, momentum and energy for the nanofluid, and continuity for the nanoparticles, is solved by a computational code which incorporates three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity and the coefficient of thermophoretic diffusion, all based on a high number of literature experimental data. The SIMPLE-C algorithm is used to handle the pressure-velocity coupling. Numerical simulations are executed using alumina-water nanofluids for different values of the diameter and the average volume fraction of the suspended nanoparticles, the plate length and position, the cavity width, the average temperature of the nanofluid, and the temperature difference imposed between the plate and the boundary walls of the enclosure. It is found that the impact of the nanoparticle dispersion into the base liquid increases remarkably with increasing the average temperature, whereas, by contrast, the other controlling parameters have just moderate effects. Moreover, when the top and bottom walls of the enclosure are cooled, keeping the sidewalls adiabatic, a periodic flow is detected, whose main features will be discussed.

scholarly journals Impact Strength of Austenitic and Ferritic-Austenitic Cr-Ni Stainless Cast Steel in -40 and +20°C Temperature

2014 ◽  
Vol 59 (3) ◽  
pp. 1103-1106
Author(s):  
B. Kalandyk ◽  
R. Zapała ◽  
Ł. Boroń ◽  
M. Solecka
Keyword(s):  
Impact Strength ◽  
Volume Fraction ◽  
Cast Steel ◽  
Testing Machine ◽  
Charpy Impact ◽  
Impact Testing ◽  
Two Phase ◽  
Steel Grades ◽  
Charpy Impact Testing ◽  
The Impact

Abstract Studies described in this paper relate to common grades of cast corrosion resistant Cr-Ni steel with different matrix. The test materials were subjected to heat treatment, which consisted in the solution annealing at 1060°C followed by cooling in water. The conducted investigations, besides the microstructural characteristics of selected cast steel grades, included the evaluation of hardness, toughness (at a temperature of -40 and +20oC) and type of fracture obtained after breaking the specimens on a Charpy impact testing machine. Based on the results of the measured volume fraction of ferrite, it has been found that the content of this phase in cast austenitic steel is 1.9%, while in the two-phase ferritic-austenitic grades it ranges from 50 to 58%. It has been demonstrated that within the scope of conducted studies, the cast steel of an austenitic structure is characterised by higher impact strength than the two-phase ferritic-austenitic (F-A) grade. The changing appearance of the fractures of the specimens reflected the impact strength values obtained in the tested materials. Fractures of the cast austenitic Cr-Ni steel obtained in these studies were of a ductile character, while fractures of the cast ferritic-austenitic grade were mostly of a mixed character with the predominance of brittle phase and well visible cleavage planes.

Two-phase model for mixed convection and flow enhancement of a nanofluid in an inclined channel patterned with heated slip stripes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Subhasree Dutta ◽  
Somnath Bhattacharyya ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Temperature Jump ◽  
Volume Fraction ◽  
Volume Flow Rate ◽  
Homogeneous Model ◽  
Jump Condition ◽  
Two Phase ◽  
Content Type ◽  
The Impact

Purpose The purpose of this study is to analyze the heat transfer and flow enhancement of an Al2O3-water nanofluid filling an inclined channel whose lower wall is embedded with periodically placed discrete hydrophobic heat sources. Formation of a thin depletion layer of low viscosity over each hydrophobic heated patch leads to the velocity slip and temperature jump condition at the interface of the hydrophobic patch. Design/methodology/approach The mixed convection of the nanofluid is analysed based on the two-phase non-homogeneous model. The governing equations are solved numerically through a control volume approach. A periodic boundary condition is adopted along the longitudinal direction of the modulated channel. A velocity slip and temperature jump condition are imposed along with the hydrophobic heated stripes. The paper has validated the present non-homogeneous model with existing experimental and numerical results for particular cases. The impact of temperature jump condition and slip velocity on the flow and thermal field of the nanofluid in mixed convection is analysed for a wide range of governing parameters, namely, Reynolds number (50 ≤ Re ≤ 150), Grashof number ( 103≤Gr≤5×104), nanoparticle bulk volume fraction ( 0.01≤φb≤0.05), nanoparticle diameter ( 30≤dp≤60) and the angle of inclination ( −60°≤σ≤60°). Findings The presence of the thin depletion layer above the heated stripes reduces the heat transfer and augments the volume flow rate. Consideration of the nanofluid as a coolant enhances the rate of heat transfer, as well as the entropy generation and friction factor compared to the clear fluid. However, the rate of increment in heat transfer suppresses by a significant margin of the loss due to enhanced entropy generation and friction factor. Heat transfer performance of the channel diminishes as the channel inclination angle with the horizontal is increased. The paper has also compared the non-homogeneous model with the corresponding homogeneous model. In the non-homogeneous formulation, the nanoparticle distribution is directly affected by the slip conditions by virtue of the no-normal flux of nanoparticles on the slip planes. For this, the slip stripes augment the impact of nanoparticle volume fraction compared to the no-slip case. Originality/value This paper finds that the periodically arranged hydrophobic heat sources on the lower wall of the channel create a significant augmentation in the volume flow rate, which may be crucial to augment the transport process in mini- or micro-channels. This type of configuration has not been addressed in the existing literature.

The Impact of Journal Bearing Wear on an Electric Submersible Pump in Two-Phase and Three-Phase Flow

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Changrui Bai ◽  
Dezhi Zheng ◽  
Robert Hure ◽  
Ramy Saleh ◽  
Nicolas Carvajal ◽  
...  
Keyword(s):  
Journal Bearing ◽  
Volume Fraction ◽  
Submersible Pump ◽  
Rotor Vibration ◽  
Two Phase ◽  
Three Body Abrasion ◽  
Three Body ◽  
Heat Checking ◽  
The Impact ◽  
Electric Submersible Pump

Electric submersible pumps (ESPs) provide artificial lift within oil wells. ESPs commonly fail from mechanical vibrations that increase as bearing clearances increase from debris, gas, and liquid pumped through the ESP. In order to understand journal bearing wear within an ESP, three stages of a mixed flow electric submersible pump were subjected to hydraulic fracture sand slurry in water. One hundred seventeen hours were conducted with sand and water, followed by 68 h with air added at 15% inlet gas volume fraction. The journal bearings were severely worn by the end of testing, and pump vibrations increased with increased bearing clearances. Bearing vibrations and clearances became significantly larger than the impeller labyrinth seal vibrations and clearances, indicating that the labyrinth seals became the dominant rotor support once the bearings were worn. Adding air increased the wear and rotor vibration orbit variability. Rotor vibration orbits were entirely independent of gas void fraction by the end of testing, indicating that the lubricant composition no longer directly impacted vibrations. Fine axial cracks from heat checking were observed on the journal of the bearings. Results indicate that controlling journal bearing wear is a critical factor for increasing operating lifetimes. Alternative bearing geometry and materials should be investigated to prevent the occurrence of three-body abrasion, limit the resultant wear rate from three-body abrasion, and limit the damage from heat checking.

The Numerical Simulation and Performance Analysis of the Vortex Pump for Solid-Liquid Two Phase Medium

2014 ◽  
Vol 527 ◽  
pp. 88-92
Author(s):  
Peng Yun Song ◽  
Hong Li Wang ◽  
Peng Cheng He
Keyword(s):  
Numerical Simulation ◽  
Volume Fraction ◽  
Internal Flow ◽  
Solid Particles ◽  
Two Phase ◽  
Pump Head ◽  
Phase Medium ◽  
And Performance ◽  
Solid Liquid ◽  
The Impact

The numerical simulation of a 3-D model of the internal flow field for a Vortex slurry pump has been analyzed in this paper. The impact of different solids volume fraction on the distribution of solid particle was analyzed. The expression of the pump head and efficiency was derived by the energy equation. The results show that either on the long blades or on the short blades, the content of the solid particles increases with the increasing of the volume fraction. The results by the expression of the pump head and efficiency are compared with the results of the simulations. The conclusions show that the expression results are similar with the numerical simulation results, and the main factors of affecting the inner and outer characteristics are the solid particles.

The Impact of Cylinder Pressure on Fuel Jet Penetration and Mixing

2002 ◽  
Author(s):  
Daniel B. Olsen ◽  
Bryan D. Willson
Keyword(s):  
Fuel Injection ◽  
Volume Fraction ◽  
Uv Light ◽  
Visible Range ◽  
Compression Process ◽  
Iccd Camera ◽  
Fuel Concentration ◽  
Fuel Jet ◽  
Jet Penetration ◽  
The Impact

Investigations of fuel jet penetration and fuel and air mixing are performed in a static piston, pressurized optical engine. The pressure in the cylinder that the gas is injected into is varied to study the effect of the compression process. The engine has the same piston and cylinder geometry as a Cooper-Bessemer GMV-4TF two-stroke cycle natural gas engine. A 14” quartz cylinder section allows the cylinder gases to be radiated with an Nd:YAG UV laser, and imaged with an ICCD camera. Nitrogen gas that is seeded with acetone, which fluoresces in the visible range when irradiated with UV light, is injected through the fuel valves. Two types of fuel injectors are studied, a low pressure (45 psi) and a high pressure (500 psi) gas injection valve. Both fuel injection valves are manufactured by Woodward Governor. Planar laser induced fluorescence is implemented to image fuel concentration within the cylinder at various times during the injection and mixing processes. Spatial standard deviations of the variations of fuel concentration (“unmixedness”) and the volume fraction of gas in the flammable range (“mixedness”) across the image plane are computed.

A Two-Phase Model for Analysis of Blood Flow and Rheological Properties in the Elastic Microvessel

2016 ◽  
Author(s):  
Xiaohui Lin ◽  
Chibin Zhang ◽  
Changbao Wang ◽  
Wenquan Chu ◽  
Zhaomin Wang
Keyword(s):  
Two Phase Flow ◽  
Volume Fraction ◽  
Transport Model ◽  
Planck Equation ◽  
Navier Stokes ◽  
Phase Flow ◽  
Two Phase ◽  
Navier Stokes Equation ◽  
Experimental Values ◽  
The Impact

The blood in microvascular is seemed as a two-phase flow system composed of plasma and red blood cells (RBCs). Based on hydrodynamic continuity equation, Navier-Stokes equation, Fokker-Planck equation, generalized Reynolds equation and elasticity equation, a two-phase flow transport model of blood in elastic microvascular is proposed. The continuous medium assumption of RBCs is abandoned. The impact of the elastic deformation of the vessel wall, the interaction effect between RBCs, the Brownian motion effect of RBCs and the viscous resistance effect between RBCs and plasma on blood transport are considered. Model does not introduce any phenolmeno-logical parameter, compared with the previous phenolmeno-logical model, this model is more comprehensive in theory. The results show that, the plasma velocity distribution is cork-shaped, which is apparently different with the parabolic shape of the single-phase flow model. The reason of taper angle phenomenon and RBCs “Center focus” phenomenon are also analyzed. When the blood vessel radius is in the order of microns, blood apparent viscosity’s Fahraeus-Lindqvist effect and inverse Fahraeus-Lindqvist effect will occur, the maximum of wall shear stress will appear in the minimum of diameter, the variations of blood apparent viscosity with consider of RBCs volume fraction and shear rate calculated by the model are in good agreement with the experimental values.

scholarly journals Buoyancy-induced convection of water-based nanofluids in differentially-heated horizontal semi-annuli

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2643-2660
Author(s):  
Alessandro Quintino ◽  
Elisa Ricci ◽  
Emanuele Habib ◽  
Massimo Corcione
Keyword(s):  
Volume Fraction ◽  
Solid Phase ◽  
Numerical Study ◽  
Brownian Diffusion ◽  
Nanoparticle Dispersion ◽  
Two Phase ◽  
Average Temperature ◽  
Effective Dynamic ◽  
Water Based ◽  
The Impact

A two-phase model based on the double-diffusive approach is used to perform a numerical study on natural convection of water-based nanofluids in differentially-heated horizontal semi-annuli, assuming that Brownian diffusion and thermophoresis are the only slip mechanisms by which the solid phase can develop a significant relative velocity with respect to the liquid phase. The system of the governing equations of continuity, momentum, and energy for the nanofluid, and continuity for the nanoparticles, is solved by the way of a computational code which incorporates three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity, and the thermophoretic diffusion coefficient, all based on a wide number of literature experimental data. The pressure-velocity coupling is handled through the SIMPLE-C algorithm. Numerical simulations are executed for three different nanofluids, using the diameter and the average volume fraction of the suspended nanoparticles, the cavity size, the average temperature, and the temperature difference imposed across the cavity, as independent variables. It is found that the impact of the nanoparticle dispersion into the base liquid increases remarkably with increasing the average temperature, whereas, by contrast, the other controlling parameters have moderate effects. Moreover, at temperatures of the order of room temperature or just higher, the heat transfer performance of the nanofluid is significantly affected by the choice of the solid phase material.

A MODELING SYSTEM FOR CLIMATE CHANGE RISK ASSESSMENT, MANAGEMENT AND HEDGING IN COASTAL AREAS

2017 ◽  
Author(s):  
Sergei Soldatenko ◽  
Sergei Soldatenko ◽  
Genrikh Alekseev ◽  
Genrikh Alekseev ◽  
Alexander Danilov ◽  
...  
Keyword(s):  
Climate Change ◽  
Risk Assessment ◽  
Coastal Areas ◽  
Mitigation Strategies ◽  
System Structure ◽  
The Arctic ◽  
Risk Modeling ◽  
Wide Range ◽  
Adverse Weather ◽  
The Impact

Every aspect of human operations faces a wide range of risks, some of which can cause serious consequences. By the start of 21st century, mankind has recognized a new class of risks posed by climate change. It is obvious, that the global climate is changing, and will continue to change, in ways that affect the planning and day to day operations of businesses, government agencies and other organizations and institutions. The manifestations of climate change include but not limited to rising sea levels, increasing temperature, flooding, melting polar sea ice, adverse weather events (e.g. heatwaves, drought, and storms) and a rise in related problems (e.g. health and environmental). Assessing and managing climate risks represent one of the most challenging issues of today and for the future. The purpose of the risk modeling system discussed in this paper is to provide a framework and methodology to quantify risks caused by climate change, to facilitate estimates of the impact of climate change on various spheres of human activities and to compare eventual adaptation and risk mitigation strategies. The system integrates both physical climate system and economic models together with knowledge-based subsystem, which can help support proactive risk management. System structure and its main components are considered. Special attention is paid to climate risk assessment, management and hedging in the Arctic coastal areas.

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