Numerical Investigation of Gas-Solid Suspension Flow in 180° Curved Duct

2007 ◽  
Author(s):  
K. A. Ibrahim ◽  
M. A. El-Kadi ◽  
Mofreh H. Hamed ◽  
Samy M. El-Behery
Keyword(s):  
Stokes Equations ◽  
Turbulence Models ◽  
Flow Behaviour ◽  
Published Data ◽  
Phase Flow ◽  
Particle Rotation ◽  
Two Phase ◽  
Curved Duct ◽  
Tracking Model ◽  
Particles Trajectories

In this paper, a two-way coupling Eulerian-Lagrangian approach is presented for the simulation of gas-solid two-phase flow in 180° curved duct. In the present study, Reynolds averaged Navier-Stokes equations (RANS) and two turbulence models namely; standard k-ε model and RNG (Renormalization Group) based k-ε model are adopted. The effects of particle rotation and lift forces are included in the particle tracking model while the effect of inter-particle collisions is neglected. The present predictions are compared with published experimental data for single-phase flow and published particles trajectories. The comparisons show that the RNG based k-ε model predicts the flow behaviour better than the standard k-ε model. Furthermore, the particles trajectories are compared very well with published data. The effects of inlet gas velocity, bend geometry, loading ratio and solid properties on the flow behaviour are also discussed. The results show that the flow behaviour is greatly affected by the above parameters.

scholarly journals A review of multiphase flow and deposition effects in film-cooled gas turbines

2018 ◽  
Vol 22 (5) ◽  
pp. 1905-1921 ◽  
Author(s):  
Jin Wang ◽  
Milan Vujanovic ◽  
Bengt Sunden
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Experimental Studies ◽  
Turbulence Models ◽  
Phase Flow ◽  
Two Phase ◽  
Film Cooling Effectiveness ◽  
Factors Affecting ◽  
Multi Phase Flow

This paper presents a review of particle deposition research in film-cooled gas turbines based on the recent open literature. Factors affecting deposition capture efficiency and film cooling effectiveness are analyzed. Experimental studies are summarized into two discussions in actual and virtual deposition environments. For investigation in virtual deposition environments, available and reasonable results are obtained by comparison of the Stokes numbers. Recent advances in particle deposition modeling for computational fluid dynamics are also reviewed. Various turbulence models for numerical simulations are investigated, and solutions for treatment of the particle sticking probability are described. In addition, analysis of injecting mist into the coolant flow is conducted to investigate gas-liquid two-phase flow in gas turbines. The conclusion remains that considerable re-search is yet necessary to fully understand the roles of both deposition and multi-phase flow in gas turbines.

On convergent schemes for two-phase flow of dilute polymeric solutions

2018 ◽  
Vol 52 (6) ◽  
pp. 2357-2408 ◽  
Author(s):  
Stefan Metzger
Keyword(s):  
Finite Element ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Phase Flow ◽  
Two Phase ◽  
Extra Stress Tensor ◽  
Spring Force ◽  
Polymeric Solutions ◽  
Fokker Planck

We construct a Galerkin finite element method for the numerical approximation of weak solutions to a recent micro-macro bead-spring model for two-phase flow of dilute polymeric solutions derived by methods from nonequilibrium thermodynamics ([Grün, Metzger, M3AS 26 (2016) 823–866]). The model consists of Cahn-Hilliard type equations describing the evolution of the fluids and the unsteady incompressible Navier-Stokes equations in a bounded domain in two or three spatial dimensions for the velocity and the pressure of the fluids with an elastic extra-stress tensor on the right-hand side in the momentum equation which originates from the presence of dissolved polymer chains. The polymers are modeled by dumbbells subjected to a finitely extensible, nonlinear elastic (FENE) spring-force potential. Their density and orientation are described by a Fokker-Planck type parabolic equation with a center-of-mass diffusion term. We perform a rigorous passage to the limit as the spatial and temporal discretization parameters simultaneously tend to zero, and show that a subsequence of these finite element approximations converges towards a weak solution of the coupled Cahn-Hilliard-Navier-Stokes-Fokker-Planck system. To underline the practicality of the presented scheme, we provide simulations of oscillating dilute polymeric droplets and compare their oscillatory behaviour to the one of Newtonian droplets.

Bounds on Two-Phase Frictional Pressure Gradient in Minichannels and Microchannels

2006 ◽  
Author(s):  
M. M. Awad ◽  
Y. S. Muzychka
Keyword(s):  
Laminar Flow ◽  
Pressure Gradient ◽  
Flow Model ◽  
Narrow Channel ◽  
Published Data ◽  
Phase Flow ◽  
Water Mixture ◽  
Two Phase ◽  
Working Fluids ◽  
Simple Rules

Simple rules are developed for obtaining rational bounds for two-phase frictional pressure gradient in minichannels and microchannels. The lower bound is based on Ali et al. correlation for laminar-laminar flow. This correlation is based on modification of simplified stratified flow model derived from the theoretical approach of Taitel and Dukler for the case of two-phase flow in a narrow channel. The upper bound is based on Chisholm correlation for laminar-laminar flow. The model is verified using published experimental data of two-phase frictional pressure gradient in circular and non-circular shapes. The published data include different working fluids such as air-water mixture and nitrogen-water mixture, and different channel diameters. The bounds models are also presented in a dimensionless form as two-phase frictional multiplier (φl and φg) versus Lockhart-Martinelli parameter (X) for different working fluids such as air-water mixture and nitrogen-water mixture. It is shown that the published data can be well bounded.

scholarly journals Slug Regime Transitions in a Two-Phase Flow in Horizontal Round Pipe. CFD Simulations

2020 ◽  
Vol 10 (23) ◽  
pp. 8739
Author(s):  
Vitaly Sergeev ◽  
Nikolai Vatin ◽  
Evgeny Kotov ◽  
Darya Nemova ◽  
Svyatoslav Khorobrov
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Bubbly Flow ◽  
Fluid Motion ◽  
Navier Stokes ◽  
Technical Solution ◽  
Phase Flow ◽  
Two Phase

The main objective of the study is to propose a technical solution integrated into the pipeline for the transition of the flow regime from slug to bubbly two-phase flow. The object of research is isothermal two-phase gas–Newtonian-liquid flow in a horizontal circular pipeline. There is local resistance in the pipe in the form of a streamlined transverse mesh partition. The mesh partition ensures the transition of the flow from the slug regime to the bubbly regime. The purpose of the study is to propose a technical solution integrated into the pipeline for changing the flow regime of a two-phase flow from slug to bubbly flow. The method of research is a simulation using computational fluid dynamics (CFD) numerical simulation. The Navier–Stokes equations averaged by Reynolds describes the fluid motion. The k-ε models were used to close the Reynolds-averaged Navier–Stokes (RANS) equations. The computing cluster «Polytechnic—RSK Tornado» was used to solve the tasks. The results of simulation show that pressure drop on the grid did not exceed 10% of the pressure drop along the length of the pipeline. The mesh partition transits the flow regime from slug to layered one, which will help to increase the service life and operational safety of a real pipeline at insignificant energy costs to overcome the additional resistance integrated into the pipeline.

scholarly journals Evaluating the Impact of Turbulence Closure Models on Solute Transport Simulations in Meandering Open Channels

2020 ◽  
Vol 10 (8) ◽  
pp. 2769 ◽  
Author(s):  
Jun Song Kim ◽  
Donghae Baek ◽  
Inhwan Park
Keyword(s):  
Solute Transport ◽  
Flow Separation ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Breakthrough Curves ◽  
Secondary Flows ◽  
Mean Velocity ◽  
Form Complex ◽  
Tracking Model ◽  
The Impact

River meanders form complex 3D flow patterns, including secondary flows and flow separation. In particular, the flow separation traps solutes and delays their transport via storage effects associated with recirculating flows. The simulation of the separated flows highly relies in the performance of turbulence models. Thus, these closure schemes can control dispersion behaviors simulated in rivers. This study performs 3D simulations to quantify the impact of the turbulence models on solute transport simulations in channels under different sinuosity conditions. The 3D Reynolds-averaged Navier-Stokes equations coupled with the k − ε , k − ω and SST k − ω models are adopted for flow simulations. The 3D Lagrangian particle-tracking model simulates solute transport. An increase in sinuosity causes strong transverse gradients of mean velocity, thereby driving the onset of the separated flow recirculation along the outer bank. Here, the onset and extent of the flow separation are strongly influenced by the turbulence models. The k − ε model fails to reproduce the flow separation or underestimates its size. As a result, the k − ε model yields residence times shorter than those of other models. In contrast, the SST k − ω model exhibits a strong tailing of breakthrough curves by generating more pronounced flow separation.

scholarly journals Simulation of Abrasion Characteristics of Polar Ship Seawater Pipelines under the Coupling of Ice Particles and Vibration

2020 ◽  
Vol 10 (4) ◽  
pp. 1349
Author(s):  
Guan-Chen Liu ◽  
Li Xu ◽  
Jie Li ◽  
Qiang Sun ◽  
Zong-Qiang Liu ◽  
...  
Keyword(s):  
Wear Rate ◽  
Flow Velocity ◽  
Two Phase Flow ◽  
Particle Diameter ◽  
Phase Flow ◽  
Particle Rotation ◽  
Two Phase ◽  
General Law ◽  
Ice Particles ◽  
Static Conditions

Under the erosion of seawater–ice two-phase flow, seawater in pipelines of polar ships can cause the pipeline failures that threaten the safety of navigations. The discrete phase model (DPM) and erosion wear model (EWM) were established by using the computational fluid dynamics (CFD) method for numerical analysis of the 90° elbow with relatively severe erosion. This paper explores the erosion effect of pipelines under different conditions and puts forward optimal measures for pipeline protection. Compared with the existing multiphase flow research, the novelty of this study is that vibration conditions are considered and parameters such as two-phase flow velocity, ice packing factor (IPF), ice particle diameter and ice particle rotation characteristics are combined with vibration conditions. Combined with the comprehensive analysis of erosion effects of static pipelines, a general law of seawater pipeline wear under vibration is obtained. The results show that pipeline wear under vibration is more serious than under static conditions. Under static conditions, the wear of the same section in the pipeline increases with the increases of two-phase flow velocity and IPF. However, under vibration conditions, when the velocity is less than 3 m/s, the wear of the pipeline has no significant change, while when the velocity is over 3 m/s, the wear rate increases significantly. The particle diameter has little effect on the wear of static pipes, but under the vibration condition, the pipe wear rate decreases with the increase of particle diameter, and it starts to stabilize when the diameter exceeds 0.3 mm. If the rotation characteristics of ice particles are taken into account, the wear rate along the pipeline is significantly higher than that without particle rotation.

Numerical Prediction of a Multistage Centrifugal Pump Performance With Stationary and Moving Mesh

2015 ◽  
Author(s):  
Alessandro Nocente ◽  
Tufan Arslan ◽  
Torbjørn K. Nielsen
Keyword(s):  
Centrifugal Pump ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Transient State ◽  
Computational Effort ◽  
Phase Flow ◽  
Two Phase ◽  
Ansys Fluent ◽  
Performance Report

The present work reviews a comparison between calculations of a steady and unsteady three dimensional (3D) flow past the diffuser channels of a centrifugal pump. The commercial software ANSYS Fluent has been used. The considered domain is one of the three stages, since each has exactly the same design. In the first part, simulations are carried out at the best efficiency point (BEP) both steady and transient state, single phase flow and four different turbulence models. Results are compared with the performance report from the manufacturer. In the second part, only the realizable k-ε turbulence model has been taken into account. The simulations have been repeated for different mass flows and the results were again compared with the data from the manufacturer. The comparison performed in the first part shows that integral quantities results are not sensibly influenced by the turbulence model. The comparison at different mass flow shows that the steady state simulations demonstrated to be a good approximation of the transient state, always containing the error within an acceptable limit. The minor computational effort needed makes it attractive to be used for further investigations which will involve two-phase flow studies on the same pump.

Study on Particle Response to Local Fluid Velocity in a Gas Particle Turbulent Flow

Volume 3 ◽  
2004 ◽  
Author(s):  
Bing Wang ◽  
Hui-Qiang Zhang ◽  
Xi-Lin Wang
Keyword(s):  
Turbulent Flow ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Similarity Function ◽  
Phase Flow ◽  
Gas Velocity ◽  
Two Phase ◽  
Waveform Similarity ◽  
Tracking Model ◽  
Particle Velocities

Solid particle response to local gas velocity was discussed based on the simulation results of instantaneous velocities of three-dimensional backward-facing step gas particle turbulent flow. Gas flow was simulated by the method of large eddy simulation and particle motion was calculated by the Lagrangian particle tracking model. Instantaneous particle response to gas velocity in two different typical flow regions was discussed. Some factors, such as the waveform similarity function and time-averaged method were used for quantitatively studying particle response regularity based on the relationship between the gas velocity and particle velocity for different size particles. It is shown that the smaller the particle is, the smaller the waveform similarity function value is. The extent that particle velocities make response to gas flow velocities in different flow regions is also distinct. Moreover, for time-averaged results, the quantitative results that particle velocities depend on gas velocities are obviously different in the main flow region. These studies also provide some reference for researches of improving particle stochastic separated flow models for turbulent two-phase flow and for studies of two-way coupling problem for two-phase flow.

Coupled solution of the Boltzmann and Navier–Stokes equations in gas–liquid two phase flow

2013 ◽  
Vol 71 ◽  
pp. 283-296 ◽  
Author(s):  
Sudarshan Tiwari ◽  
Axel Klar ◽  
Steffen Hardt ◽  
Alexander Donkov
Keyword(s):  
Two Phase Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Phase Flow ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Coupled Solution

Steady and Dynamic Models of Fuel and Air Flow in Carburetors for Small Engines

2005 ◽  
Vol 127 (4) ◽  
pp. 778-786 ◽  
Author(s):  
Diego A. Arias ◽  
Timothy A. Shedd
Keyword(s):  
Dynamic Models ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Small Diameter ◽  
Phase Flow ◽  
Flow Conditions ◽  
Dynamic Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Small Engines

This work presents the mathematical model of a complex flow network containing short metering orifices, compressible flow, and two-phase flow in small diameter pipes. It has been developed to study the steady and dynamic flows in a carburetor for small engines. It extends the previously published models by incorporating a detailed review of two-phase flow pressure drop, the effect of the fuel well on the control of air-bleed flow, and dynamic flow. The homogeneous two-phase flow model, which is commonly used in previous models, was compared to an empirical correlation derived from experiments in small pipes and found to be in poor agreement. In order to assess dynamic flow conditions, the model was extended by solving instantaneous one-dimensional Navier-Stokes equations in single-phase pipes. This strategy proved successful in explaining the mixture enrichment seen under pulsating flow conditions. The model was also used to derive a sensitivity analysis of geometries and physical properties of air and fuel.

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