A Hybrid Method for Simulating Flows Including Fluid Particles

2006 ◽  
Author(s):  
Akiyoshi Maeda ◽  
Akira Sou ◽  
Akio Tomiyama
Keyword(s):  
Particle Tracking ◽  
Hybrid Method ◽  
Large Scale ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Particle Diameter ◽  
Interface Tracking ◽  
Wide Range ◽  
Standard Interface ◽  
Dynamics Method

A hybrid CMFD (computational multi-fluid dynamics) method is proposed for the prediction of multiphase flows including large-scale interface, poly-dispersed bubbles and/or drops. The method is the hybrid integration of an interface tracking method (ITM), three kinds of particle tracking methods (PTM) and an averaging method based on a multi-fluid model (MFM). The integration enables us (1) to cover a wide range of d* = d/Δx, where d is the particle diameter and Δx the grid size, and (2) to perform various kinds of multiphase CFD such as standard interface tracking, particle tracking and multi-fluid simulations, and hybrid simulations using an arbitrary combination of ITM, PTM and MFM. The field and constitutive equations of the proposed method are described in detail. A poly-dispersed air-water bubbly flow and several bubble plumes in a small open vessel are simulated using the proposed hybrid method to demonstrate its potential.

scholarly journals Uncertainty Quantification of the Hybrid Method for Particle Field Measurement Using Digital In-Line Holography

2013 ◽  
Author(s):  
Jian Gao ◽  
Jun Chen ◽  
Daniel R. Guildenbecher ◽  
Phillip L. Reu
Keyword(s):  
Hybrid Method ◽  
Field Measurement ◽  
Particle Diameter ◽  
Detection Algorithm ◽  
Field Conditions ◽  
Flow Measurements ◽  
Shape Information ◽  
Particle Field ◽  
Depth Measurement ◽  
Wide Range

Digital in-line holography has been applied extensively to particle field measurement, where the particles can be the tracer particles for flow measurements, droplets in spray diagnostics, or aquatic microorganisms. The particle detection algorithm plays a key role in accurate detection of particle 3D locations and sizes. A hybrid method has recently been proposed for particle field measurement in digital in-line holography. It features automatic determination of the threshold for segmentation of the particle field and the capability to measure particles of arbitrary shapes. Using the hybrid method, the particle 3D location, size and shape information can be extracted. The uncertainty of the hybrid method is characterized using both synthetic and experimental holograms at different particle field conditions. The depth measurement uncertainty is within 2 times the particle diameter for a wide range of particle field conditions.

Numerical Prediction of Pressure Gradient of Slurry Flows in Horizontal Pipes

2013 ◽  
Author(s):  
Gianandrea Vittorio Messa ◽  
Michael Malin ◽  
Stefano Malavasi
Keyword(s):  
Pressure Gradient ◽  
Large Scale ◽  
Solid Phase ◽  
Fluid Model ◽  
Operating Conditions ◽  
Sand Particle ◽  
Horizontal Pipes ◽  
Numerical Predictions ◽  
Wide Range ◽  
Solid Liquid

Pipe flows of solid-liquid mixtures in the form of slurries are frequently encountered in many engineering applications. The pressure gradient is perhaps the most serious concern of designers, as it dictates the selection of pump capacity. Due to their versatility, in the sense of applicability to large scale systems and more complex flows, CFD models have been an attractive tool in recent years. The fully-suspended flow of solid-liquid slurries in horizontal pipes is simulated by means of a two-fluid model. In particular, the effect of the wall boundary condition for the solid phase on the pressure gradient is discussed, considering different alternatives. The numerical predictions were compared to experimental measurements from open literature over a wide range of operating conditions, in terms of pipe diameter (53.2 to 103 mm), grain material (glass beads and sand), particle size (90 to 370 μm), slurry velocity (1.5 to 8 m/s), and mean solids concentration (up to 40%). The equilibrium wall function of Launder and Spalding for smooth walls proved adequate for fully-suspended flows, but overestimates the losses if the particles are large compared to the boundary layer thickness. Guidelines are provided for defining the numerical set-up and evaluating the uncertainty of the numerical results.

A Multi-Fluid Model Coupled With Interface Tracking Method for Simulation of Liquid Jet Breakup

2018 ◽  
Author(s):  
Mingjun Zhong ◽  
Yuan Zhou
Keyword(s):  
Large Scale ◽  
Fluid Model ◽  
Coupled Model ◽  
Current Method ◽  
Vof Method ◽  
Liquid Jet ◽  
Interface Tracking ◽  
Tracking Method ◽  
Breakup Length ◽  
Jet Breakup

For liquid jet breakup, when small drops are fragmented from the surface of jet, the fluid’s interfaces with various length scales will coexist in the flow regimes. The paper presents a coupled method to simulate liquid jet breakup. The present method is based on Yan and Che’s strategy which has been proven to be capable for simulation of bubbly-slug flow. In the method, the basic multi-fluid model and interface tracking method are coupled by a unified solution frame work of MCBA-SIMPLE algorithm. The jet phase and continuous liquid phase are combined into a continuous phase in order that the large-scale interface of jet can be reconstructed by VOF/PLIC method. The coupled model consists two sub-models, the model based on VOF method and the conventional multi-fluid model; The relationships and switching of the sub-models are disused and summarized in the paper. Some cases are presented to show the capabilities of the current method. Firstly, the sub-model which is equivalent to the VOF method is used to simulate the interface behavior during the jet breakup and a breakup length equation is correlated. Then the coupled model is applied to the same simulation. A simple jet breakup model is used to simulate mass transfer of drops from jet. Variation of the drop surface area is considered by solving a transport equation. The simulation results preliminarily show that the current method is capable to simulate the complex jet breakup process. The main characteristics of the process such as breakup length and drops distribution are reasonably simulated.

CFD Modeling of Subsea Gas Releases Using an Improved Bubble Drag Law

2017 ◽  
Author(s):  
Mustafa C. Kara ◽  
Mazdak Parsi ◽  
Anchal Jatale ◽  
Partha P. Sharma
Keyword(s):  
Large Scale ◽  
Oil And Gas ◽  
Bubbly Flow ◽  
Significant Risk ◽  
Cfd Modeling ◽  
Gas Release ◽  
Bubble Plume ◽  
Two Phase ◽  
Wide Range ◽  
Drag Law

A subsea gas leakage from pipelines, risers, gas transport pipelines or blowouts from oil and gas wells forms dispersion of gas as it rises to the surface. Accidental subsea gas release scenarios of hydrocarbons pose a significant risk for the safety and integrity of offshore production or drilling units. With recent advancements in technology, the number of subsea installations and pipelines increases substantially at larger water depths. For the large depths, it is crucial to understand the quantitative impact of the gas release as the classical integral bubble plume models fail to predict gas flux and gas distribution through the ocean surface and the resulting surface flows. A quantitative multiphase computational fluid dynamics (CFD) model can be implemented to simulate large scale bubble plumes by tracking bubbles and free surface in a Eulerian-Lagrangian fashion. In this paper, the coupled discrete phase (DPM) and volume of fluid (VOF) multiphase modeling approach has been utilized for modeling subsea gas releases. This study evaluates an improved drag law for gas-liquid two phase bubbly flow based on consideration of bubble deformation. The model successfully predicts a wide range of experimental measurements at model scale and is also applied to gas release at large ocean depths to study the validity of the model for realistic scenarios.

scholarly journals Dense granular flow rheology in turbulent bedload transport

2016 ◽  
Vol 804 ◽  
pp. 490-512 ◽  
Author(s):  
Raphael Maurin ◽  
Julien Chauchat ◽  
Philippe Frey
Keyword(s):  
Granular Flow ◽  
Large Scale ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Particle Diameter ◽  
Bedload Transport ◽  
Spherical Particles ◽  
Granular Rheology ◽  
Wide Range ◽  
Dense Granular Flow

The local granular rheology is investigated numerically in turbulent bedload transport. Considering spherical particles, steady uniform configurations are simulated using a coupled fluid–discrete-element model. The stress tensor is computed as a function of the depth for a series of simulations varying the Shields number, the specific density and the particle diameter. The results are analysed in the framework of the $\unicode[STIX]{x1D707}(I)$ rheology and exhibit a collapse of both the shear to normal stress ratio and the solid volume fraction over a wide range of inertial numbers. Contrary to expectations, the effect of the interstitial fluid on the granular rheology is shown to be negligible, supporting recent work suggesting the absence of a clear transition between the free-fall and turbulent regimes. In addition, data collapse is observed up to unexpectedly high inertial numbers $I\sim 2$, challenging the existing conceptions and parametrisation of the $\unicode[STIX]{x1D707}(I)$ rheology. Focusing upon bedload transport modelling, the results are pragmatically analysed in the $\unicode[STIX]{x1D707}(I)$ framework in order to propose a granular rheology for bedload transport. The proposed rheology is tested using a 1D volume-averaged two-phase continuous model, and is shown to accurately reproduce the dense granular flow profiles and the sediment transport rate over a wide range of Shields numbers. The present contribution represents a step in the upscaling process from particle-scale simulations towards large-scale applications involving complex flow geometry.

Electron microscopy study of reactively sputter-deposited Ti/N films on silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1362-1363
Author(s):  
V. C. Kannan ◽  
A. K. Singh ◽  
R. B. Irwin ◽  
S. Chittipeddi ◽  
F. D. Nkansah ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Large Scale ◽  
Hexagonal Phase ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Process Conditions ◽  
Tin Films ◽  
Wide Range ◽  
Fcc Phase ◽  
Circuits Vlsi

Titanium nitride (TiN) films have historically been used as diffusion barrier between silicon and aluminum, as an adhesion layer for tungsten deposition and as an interconnect material etc. Recently, the role of TiN films as contact barriers in very large scale silicon integrated circuits (VLSI) has been extensively studied. TiN films have resistivities on the order of 20μ Ω-cm which is much lower than that of titanium (nearly 66μ Ω-cm). Deposited TiN films show resistivities which vary from 20 to 100μ Ω-cm depending upon the type of deposition and process conditions. TiNx is known to have a NaCl type crystal structure for a wide range of compositions. Change in color from metallic luster to gold reflects the stabilization of the TiNx (FCC) phase over the close packed Ti(N) hexagonal phase. It was found that TiN (1:1) ideal composition with the FCC (NaCl-type) structure gives the best electrical property.

THE SOME QUESTIONS OF AUTONOMOUS MOTION AND MANAGEMENT OF LAND-MOBILE ROBOTIC COMPLEXES FOR UKRAINIAN GROUND FORCESE

2019 ◽  
pp. 53-58
Author(s):  
О. Кravchuk ◽  
V. Symonenkov ◽  
I. Symonenkova ◽  
O. Hryhorev
Keyword(s):  
Large Scale ◽  
Armed Forces ◽  
Distributed Information ◽  
Wide Range ◽  
Highly Effective ◽  
Information Management Systems ◽  
Robotic Devices ◽  
Principles And Standards ◽  
And Control ◽  
The Eu

Today, more than forty countries of the world are engaged in the development of military-purpose robots. A number of unique mobile robots with a wide range of capabilities are already being used by combat and intelligence units of the Armed forces of the developed world countries to conduct battlefield intelligence and support tactical groups. At present, the issue of using the latest information technology in the field of military robotics is thoroughly investigated, and the creation of highly effective information management systems in the land-mobile robotic complexes has acquired a new phase associated with the use of distributed information and sensory systems and consists in the transition from application of separate sensors and devices to the construction of modular information subsystems, which provide the availability of various data sources and complex methods of information processing. The purpose of the article is to investigate the ways to increase the autonomy of the land-mobile robotic complexes using in a non-deterministic conditions of modern combat. Relevance of researches is connected with the necessity of creation of highly effective information and control systems in the perspective robotic means for the needs of Land Forces of Ukraine. The development of the Armed Forces of Ukraine management system based on the criteria adopted by the EU and NATO member states is one of the main directions of increasing the effectiveness of the use of forces (forces), which involves achieving the principles and standards necessary for Ukraine to become a member of the EU and NATO. The inherent features of achieving these criteria will be the transition to a reduction of tasks of the combined-arms units and the large-scale use of high-precision weapons and land remote-controlled robotic devices. According to the views of the leading specialists in the field of robotics, the automation of information subsystems and components of the land-mobile robotic complexes can increase safety, reliability, error-tolerance and the effectiveness of the use of robotic means by standardizing the necessary actions with minimal human intervention, that is, a significant increase in the autonomy of the land-mobile robotic complexes for the needs of Land Forces of Ukraine.

Stirring and aeration system for the upgrading of small waste water treatment plants

1994 ◽  
Vol 29 (12) ◽  
pp. 149-156 ◽  
Author(s):  
Marcus Höfken ◽  
Katharina Zähringer ◽  
Franz Bischof
Keyword(s):  
Waste Water ◽  
Water Treatment ◽  
Large Scale ◽  
Waste Water Treatment ◽  
Water Treatment Plants ◽  
Waste Water Treatment Plants ◽  
Basic Fluid ◽  
Aeration System ◽  
Technical Realization ◽  
Wide Range

A novel agitating system has been developed which allows for individual or combined operation of stirring and aeration processes. Basic fluid mechanical considerations led to the innovative hyperboloid design of the stirrer body, which ensures high efficiencies in the stirring and the aeration mode, gentle circulation with low shear forces, excellent controllability, and a wide range of applications. This paper presents the basic considerations which led to the operating principle, the technical realization of the system and experimental results in a large-scale plant. The characteristics of the system and the differences to other stirring and aeration systems are illustrated. Details of the technical realization are shown, which conform to the specific demands of applications in the biological treatment of waste water. Special regard is given to applications in the upgrading of small compact waste water treatment plants.

Thin structure of heterogeneous and multiphase fluid flows

2012 ◽  
Vol 9 (1) ◽  
pp. 175-180
Author(s):  
Yu.D. Chashechkin
Keyword(s):  
Large Scale ◽  
Fundamental System ◽  
Fluid Flows ◽  
Regular Solutions ◽  
Flow Models ◽  
Group Methods ◽  
Wide Range ◽  
Thin Structure ◽  
Multiphase Fluid ◽  
Complete Solutions

According to the results of visualization of streams, the existence of structures in a wide range of scales is noted: from galactic to micron. The use of a fundamental system of equations is substantiated based on the results of comparing symmetries of various flow models with the usage of theoretical group methods. Complete solutions of the system are found by the methods of the singular perturbations theory with a condition of compatibility, which determines the characteristic equation. A comparison of complete solutions with experimental data shows that regular solutions characterize large-scale components of the flow, a rich family of singular solutions describes formation of the thin media structure. Examples of calculations and observations of stratified, rotating and multiphase media are given. The requirements for the technique of an adequate experiment are discussed.

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