Science topic

Multi Phase Flows - Science topic

Singular limits-interfaces-existence theory
Questions related to Multi Phase Flows
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hi everybody i'm work on PDF based description of particles-laden turbulent flow. does this subjet interest any body her ?
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Hi, are you interetsing in the theoretical or in the numerical part?
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I need to define mass transfer in two-phase mixture of nanofluid.
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Hi Dastmalchi,
Two distinct multiphase flow models are available in ANSYS CFX, an Eulerian-Eulerian multiphase model and a Lagrangian Particle Tracking multiphase model. Information on the use of the Lagrangian Particle Tracking model is available in Particle Transport Modeling. You will find a lot of articles and tutorials on multi-phase flow in ANSYS CFX.
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I am working on solving fluid flow problems. Mainly using vorticity stream function formulation. In that getting problem to write a code. I am using c++ code for programming. I ve boundary conditions for stream function on entrance, top and bottom. For vorticity i ll get from stream function vorticity transport equation. Can anyone one help me to write a logic for solving vorticity streamfunction formulation?
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I wrote Fortran code for this some years ago, which has been used for work which I've published. I also have a grid generator so that the solver can be used for general 2-d geometries. If you can send me your email address I'm happy to send you these codes. It should then be fairly easy for you to translate the relevant parts of the code from Fortran to C++ to put into your own code.     
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I'm working on 1 phase multi component flow in channel with Shan & Chen approach, I have 3 component(Ideal gases) in my simulation. I've wrote streaming and collision steps codes for each component, then composite velocities have been obtained and have used as alternative in streaming step velocity in each component. but I cant reach to good answers. would you can help me about this problem?
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Look at this doc it may be helpful for your topic. Good luck
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Dear colleagues,
what are the minimal grid requirements regarding cell size and particle diameter? I have a grid with average cell volume greater then particle volume in a Eulerian-Lagragian model. However, close to the impeller (MRF rotating zone), the cell size are much smaller for correctly resolving the Boundary Layer. In this case, the particle (volume) occupies the volume of 2 or more cells. What are the implications in the continuity and momentum equaion (2-way-coupoling)? Is there a problem? How do I solve the problem? Does anyone know any study in this regard?
Thank you in advance.
Best wishes,
Jose
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Hi Jose,
As far as I know, the typical models for Lagrangian Particle Tracking, like drag force model, etc (that are widely used in literature) are based on the assumption that the particle diameter is considerably smaller than the cell size, say dp < cellSize/10.
This assumption is sometimes called "undisturbed fluid velocity".
When you can not use larger grid cells (due to limitations in the boundary layer, for example)  you may use some possible solutions. One way is to use a multigrid technique; I mean a coarse grid for Lagrangian part and a fine grid for the Eulerian one.
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Hi everyone,
I am a PhD student working on a solar still desalination system. 
I need to capture the condensation rate on the cover or outlet. 
I have achieved some progress but I need some help here.
Regards,
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Can you send details to my e maik id, abdulsamad@gectcr.ac.in
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in the small diameters (or depth for rectangular one) the trickle flow can't be exist. am I right? what is the threshold?
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Hi Stainstaw Anweiler,
I want to make a trickle regime that gas and liquid simultaneously flow through a soild porous medium and the problem is with making the physical flow. I read some papers about trickle flow and the minimum depth that i found was about 3cm for rectangular cross section and in one paper the *hydraulic* diameter for an annulus bed was 2cm. for the most 2D beds, depth was smaller than 1cm. but i don't want a 2D bed.
I will be happy if it's possible to make a rectangular cross section trickle bed with 1.4cm depth.
thanks for your answer
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I have solving a 2D oil water multi phase flow in a horizontal pipe having L=12m and D=0.036.The flow characteristics covered the range of mixture velocities from 0.1 to 1.5 m/s and input oil volume fractions from 0.1 to 0.9.
I make a line along vertical direction at (X0=12, Y0=0 AND X1=12,Y1=0.036), then  I go to XY plot section, I choose Y-axis as a pressure gradient(under derivative section i get pressure grad option) but in X -axis how I selected input oil fraction as a option???
For getting input oil fraction as a X-axis variable, I Used custom field function in fluent  but I don't know what is the formula to calculate it???
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Dear Prantik...
You don't need to use Custom Field function. You only have to define a parameter or function in Monitoring tab of fluent software.
For more information, my educational mail is:
BR
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May someone help in understanding the difference between phase-field method and level-set method?
Thank You
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Both of these methods are the kinds of volume tracking methods. Also, VOF is another kind of volume tracking method. These methods use different criteria for finding that which phases are placed in which cells.
LSM uses a function that describes the smallest distance from the interface as a criteria. In the first phase, this distance is positive and in another one is negative. Numerical solution of advection eq. Of the function of distance estimate the position of the interface.
In the phase-field method the criteria is a function (phase field function) of [-1,+1], that in first phase area this function is +1 and in another one is -1. Using this function the interface is where that this function is zero. This function has smooth variation, in a narrow area near the interface.
This paper can be helpful I think,
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I had considered a square domain with a particle at the center. The gas molecules are distributed randomly inside the domain only with thermal velocities without bulk component. I had made gas and body temperatures to be same. DSMC simulations give non zero force value which is very less. Shall I consider the force is Brownian force or it is statistical error?
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Dear all,
I write for suggestion about the new research points and gaps to write a research proposals in multi-phase flow (reactive and/or non reactive) and Fluid structural interaction.
I appreciate your suggestions and help.
Many thanks, Mohamed
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Hello,
Why  do Cahn Hilliard Equation need to satisfy non-linear stability relationship? 
Why does this condition poses constraint to design stable numerical schemes for Phase-field modelling?
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@Deewakar  I change it by the exact doc that I want upload. Good luck.
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I am simulating a multi phase flow with liquid and a gas in COMSOL. Volume fraction of the gas exceeds 1, which is not possible logically.
What is going wrong?
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Check boundary conditions and keep an eye on mass balance. You may find when and why this exceeds 1.
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I am working on multi-phase flow in a pipe with water and sand as two fluid phase and solved it in Eulerian model but i don't know how to create a Chord Averaged Volume fraction profile for sand about Z axis.
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One way would be to create a line in ANSYS FLUENT itself, and then under reports set a surface monitor -> vertex average -> whatever property you want to average. Good luck!
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I am working on multi-phase flow in a pipe with water and sand as two fluid phase and solved it in Eulerian model but i don't know how to create a Chord Averaged Volume fraction profile for sand about Z axis.
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I want to model CO2 multi phase flow inside ejector .Please help me in this reards.
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Can anyone tell me how to calculate volume fraction boundary condition for secondary phase ( Biomass) for three phase fluidized bed reactor working with air as a primary phase and sand and biomass as secondary phase
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I am a beginner in CFD and this might be a trivial question:
As far as I know, when we solve for liquid flow with a free surface in theoretical analysis, we always neglect the existence of air (due to low viscosity). In other words, we only bother with the liquid phase. But with CFD, it seems that we should use VOF method to capture the liquid surface. Consequently, it seems we have to use multi-phase flow and introduce the gas phase as the one of the phases. Just wonder do we have to always do that with CFD method? What if I want to simulate liquid flow with a free surface in vacuum, where there's indeed no gas phase? Any relevant answer is highly appreciated.
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I think, that in vacuum a liquid surface would instantaneously start to boil off, since in vacuum the pressure is much below the vapor pressure of the liquid.
This shows, that the empty space above the liquid surface needs to be filled with something, which is at the same pressure condition as the liquid on its surface. Furthermore wave effects might occur due to the interaction between the gaseous phase and the liquid phase, if not the very trivial case is considered, that both phases are at rest, i.e. not moving. Otherwise a shear stress is occurring on the free surface, and this needs to be taken into account.
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Hello! I am working on my thesis regarding VOF modeling of flow in open channels. The issue is that by specifying transient state conditions for the multi-phase flow, the solution is unable to converge even for large number of iterations. What should be the optimum value of time step size and number. Also, what should be the convergence criteria for this case. Regards
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Little detail given about your application and what you like to accomplish. So difficult to give any advice.
Are you attempting to run your case in steady-state or is it already a transient simulation. If the latter, switch to pseudo-transient method with coupled solver, if not already done so. You can run Fluent with automatic timestep setting, switching verbosity to 1. In this case Fluent tells you, what automatic timestep it has determined and is using. Try to systematically reducing the timestep from this automatic timestep selection by subsequent division by factor of 2 and see, what influence this has on convergence.
In addition you might want to calculate the Courant number based on the maximum occurring velocity in your domain and the governing cell size in this location. If this Courant number is rather high for the used timestep size (high means something between 10 and 100), you might want to reduce the timestep to get Courant number closer to unity. Or you might want to make your mesh more isotropic in this location.
Regards,
Th. Frank.
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what is the distinction between these two flows?
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I agree with the answer of Ioan David . It provides a good definition and gives an imagination of the differences, which might be required in the modeling treatment for the both different kinds of flows.
A granular flow is essentially a mixture of a granular (particle) material and one fluid - the latter might be e.g. air or water. Examples are e.g. circulating fluidized beds or sand transport in river beds.
An example for debris flow might be e.g. a mud slide on a hill face, where sand, gravel and stones of different sizes are premixed to the mixture of clay, mud and water. Other flows of similar kind might be named as debris flows as well. Consequently the model description of this kind of flow is much more difficult in comparison to a granular flow, because the relationship for the acting stress tensor and the governing viscous forces might e.g. widely depend on the water content of the debris flow and ranging from a plastic, highly-viscous and rather creeping (low velocity) flow behavior to a rather water-like and more Newtonian flow behavior. The presence of a whole spectrum of particle/debris sizes over several orders of characteristic diameter range adds an additional degree of complexity.
Regards,
Dr. Th. Frank.
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I want to flow air inlet in porous media and water-vapor outlet and heating air by using radiation model with solar load. Can I do it? If yes, so how can I apply it?
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Thanks, Neeraj for reply, how can I used porous media with mixed flow in ansys fluent.
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Hello all,
I have been going through one of the article (related to phase field modelling). However, there are few things which I am not able to get. (The article is attached along with and is titled "A Variational Approach to Deriving Smeared-Interface Surface Tension Models by D. Jacqmin"
May anyone help in this regard?
Thanks
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You can start with the basic concepts in this article:
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I am evaluating a multiline anchor systems for use in floating offshore wind turbine farms. To fully evaluate this concept, it need to analyse it for a variety of water depths and inter-turbine spacings.
I need to create rough/approximate designs of the mooring systems for floating offshore wind turbines at various water depths. I understand that the offset limit of a FOWT is governed by the bending radius and tension limits of the power cable/umbilical, but the design of the power cable/umbilical is not within the scope of my project. I understand offset limit increases with depth, and I know that 6-8% of the water depth is a good starting point for offset limits of O&G platforms. I do not think this O&G offset limit method appropriate to use for FOWTs because FOWTs have larger allowable platform motions.
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Reed this book, it may be helpful for your topic. Good luck.
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A wrong theory in physics: theory of Entropy
Entropy:A concept that is not Physical Quantity
shufeng-zhang uhsgnahz@126.com
Central-South University China
This paper demonstrates entropy is not a physical quantity.
We define heat engine efficiency η as: η= W/W1, that is, replacing Q1 in the original definition η=W/Q1 with W1, W still is the net work of the heat engine applied to the outside in one cycle, W1 is the work the heat engine applied to the outside in the cycle, then, we use Stirling cycle as the element reversible cycle , if ∮dQ/T =0 is tenable, we can prove ∮dW/T =0 and ∮dE/T =0.
If the formula ∮dQ/T=0, ∮dW/T=0 and ∮dE/T=0 can really define new system state variables, it comes to the absurd result of such a definition.
In fact, during the process of obtaining “entropy”, ∑[(ΔQ)/T)] becomeing ∫dQ/T is untenable, therefore, the formula ∮dQ/T=0, ∮dW/T=0 and ∮dE/T=0 are untenable.
The“entropy”defined by Boltzmann is used to interpret “entropy” by Clausius, so, it is at the same time denied.
The whole paper:
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I am sorry but I cannot agree. It seems that you have spread your "paper" in some forums but if you are a researcher you should know that this is not science. This is more like gossip.
If you are convinced that your paper is correct submit it for publication in some peer-reviewed journal of high-impact factor and that's the way you will also test your proof. Indeed, the fact that you have written something does not make it true necessarily.
On the other hand, I strongly recommend you to go through a textbook of differential geometry and especially through the proof of existence of integrating factors. Especially for the case of an ideal gas the proof is almost trivial.
In general thermodynamics is much more mathematically oriented than many people think whereas its experimental validity in local equilibrium and equilibrium states is beyond doubt.
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I am modeling the closed vessel which is exposed to heat, and it is multi-component case included C1,C2,C3,N2,H2O,CO2 (with defined composition), in multiphase condition, and evaporation and condensation occurs in this case.
in Eulerian model in Fluent , we should fix number of phases, in this case what should i enter in number of phases?
does each bubble shaped in liquid phase count as a separate phase?
Is it true that each place which has different composition with other place counted as two seperate phase?
I will appreciate if someone explain this
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Of course you can define three phases if the two liquid phases are immiscible. Be aware of using a characteristic particle (bubble/droplet) diameter, which is representiive for your system. Alternatively, a population balance model could be used, but this makes calculations much more difficult and requires information about the size distribution. Depending on the pressure it may be required to integrate boiling models if the maximum temperature is 100 °C. Some details on the available models are explained in section 17.7.5 of the Fluent theory guide. Unfortunately, I never had to use those models and, thus, I don't know any details about the numerics and/or their stability.
Regards, 
Stephan
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I have been trying to simulate droplet falling, impact and spreading. I have used COMSOL and Fluent. I got some results but they are not satisfactory. Is there anyone who worked on similar things? I need to :
1) define an initial velocity of the droplet
2) apply dynamic contact angle during spreading
For COMSOL, the droplet don't deform that much after the impact.and for fluent I having trouble defining a free / open boundary. I have been using pressure inlet for free boundary. Here is some simulation result.
1. VOF+Level Set - with surface tension - with wall adhession (https://www.youtube.com/watch?v=P4VkHX9UYeE)
2. VOF+Level Set - with Surface Tension - no wall Adhession (https://www.youtube.com/watch?v=4UVQ-AM-vkY)
3. VOF (no Level Set) - without surface tension - no wall adhession (https://www.youtube.com/watch?v=rtVbNEHD6zE)
Can anyone help me regarding regarding my queries?
1. How can I assign initial velocity for the droplet?
2. How can I get more realistic deformation?
3. How can I apply wetted / non-wetted surface condition?
4. How do I implement dynamic contact angle?
Can anyone tell me whether Smooth Particle Hydrodynamics (SPH) is a better option for this problem?
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I think those droplets are big enought that you should be able to use the Stoke's settling velocity as a decent estimate, though less than about twenty microns might need a better estimation. Ther teminal velocity of the 100 micron and smaller droplets is surprisingly slow. Down to about 10 microns they fall so slowly that I suspect the surface tension is going to overwhelm much of your other deformation simulations.
A good first step might be to plot your settling velocity for your range of particle diameters. (They're droplet shaped, but you can use the aerodynamic diameter, which is basically the average diameter.) I suspect that you're going to see that you'll need a few different simulations for the impact and spreading.
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I have to simulate a feed nozzle design for FCC (Fluidized Catalytic Cracking) column in a petroleum refinery. It is a multiphase problem. For this, I am asked to choose the most appropriate simulation package b/n COMSOL and FLUENT?
Can anyone help me in this regard by sharing your views on which is best for solving such cases?
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I am trying to simulate the motion of water drop over an oil surface through VOF in FLUENT. I face loads of issues related to the dynamic contact angle:
1.There is no option to change the contact angle between oil surface and water droplet.
2. From the literature there is no result for prediction of the dynamic contact angle between oil surface and droplet (when the droplet is moving).
3. Due to these issues, I now doubt the validity of VOF in this case. Are there any other methods like Lattice Boltzmann,etc. that can capture the movement of water droplet over oil surface ?
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Dear Manjunath,
unfortunately I am not an expert in VOF and FLUENT. However, I know a bit about modelling of bilayer systems, i.e. fluid flow on fluids with contact lines etc. From my viewpoint motion on a liquid is very different from motion over a solid. On the solid with no-slip condition you have the well-known contact-line paradox, which makes the behaviour of moving contact lines very much dependent on the physics and chemistry of the liquid/solid surface. Basically you only get motion with finite contact angle if you regularize near the contact line.
This paradox is absent on a liquid layer (substrate), because the lower liquid (in your case the oil) can flow with the water drop. That is why you would expect an equilibrium contact angle even in a non-equilibrium flow situation (assuming there are no Marangoni forces, surfactants, etc.). This is probably explains that you don’t find any literature about it. Note that the situation might be somewhat different for complex liquids or if the viscosities of both liquids are very different (many orders of magnitude).
In this sense I would suspect a VOF with equilibrium contact angles to give good results.
Regards
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Please suggest the latest topics on multi-phase systems (especially on transmission lines with more than 3-phase) to start my research work.
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I think that poli-phase (more than 3-phases) transmission systems were used in the past by Russians, but now I dont know about their use for transmission. When you need to increase energy volumes to be transported, you can use a double circuit overhead line, but it remains a double-three-phase line. On the other hand, to transport huge volumes of power through long distances, HVDC lines are now used. The trend for those lines has been the increasing of the voltage to increase their transport capability.
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Which are the best free surface flow (theory and computational) book? I'm trying to understand the different methods for free surface flow calculation using 3D Navier-Stokes and Continuity Equations.
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Dear All,
I would like to ask you, in Fluent Multi-phase flow (Eulerian), 
How secondary phase block primary phase ?
If my have very high fraction of secondary phase, the primary will be blocked or change the direction or velocity.
Anyone can explain mechanism or physics underlying this situation?
Best Regards,
Yannapol S.
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What are your primary and secondary phase volume fractions and velocities at the inlet boundary?
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Why does the transverse length scale of turbulent flow have a negative region?
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2D or 3D flow ?, incompressible ? and I am not sure, what do you mean by "negative region" ?
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Hi,
Regarding compressible flow with shock waves: (for example shock-bubble interaction)
1. Why HLL is more dissipative than HLLC?
2. What is better to implement? First-order HLLC or second-order HLL? As we know high-order scheme are still first order accurate in the vicinity of shocks.
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The HLL solver assumes a two-wave configuration: Two signals, separating three states. That works for hyperbolic equations, but as soon as you have a larger system, such as presented by the Euler equations, it is no longer correct and your end result may well be completely wrong. In a general case, I would advice implementing HLLC, which restores the third wave. It makes the code much more flexible.
For some more information, I would recommend the link below. In any case, the pros and cons of such solvers are explained in any good book on numerical hydrodynamics
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for effective average pore pressure there was but i don't know for density of three -phase flow. If you can help me for understanding, i would like to say thank you very much. 
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I join also the chapter 14 of "environmental geomechanics" (Schrefler & Delage  eds),Wiley Iste, 2010 which contains some data.
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Dear sir/madam, I am working on multi-phase fluid flow in micro-channel. I want to study the fluid flow behaviour, particles deposition and its effect on constricted channel. My inlet is composed of water (density = 1003 kg/m3, viscosity = 0.001 kg/ms) and particles (having density=1096 kg/m3, diameter of particle=8 microns). I am assuming the particles as spherical  micro or nano particles. Which modelling method is proper to simulate the above conditions and which model I have to use in Fluent. I also want to know about particles tracking and its deposition. Please suggest me related tutorials,papers and links. 
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Abdulrajak Buradi, with 8 microns particle size diameter, these are not nanoparticles; while with nanoparticles, any liquid will behave non-Newtonian at any concentration, with micron sized partiles this will only happen at some higher concentration.(unclear which one, depends on the surface tension of the particles) 
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Hello,
I am studying on multi phase flow with multi species and i wonder in your simulations what is the volume fractions of air or water at inlet?
Thanks
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hello i dont have the full project but i think the size of channel or pipe effect on volume fraction at inlet
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Hello,
I am dealing with CFD analysis of Heat exchanger of Shell and Tube type. Evaporator is of shell and Tube type, hot steam is getting condensed in shell side and cold water is getting evaporated inside the Tubes.
I want to model condensation & evaporation of in a single Heat Exchanger.
For clear understanding I have attached one sketch as well,
Please do reply If you have any idea how to deal with such problems this. Which multi phase model should be used?
Any Tutorial/Videos/links can help to get some basic info on how to model?
Thanks
Regards,
Somnath Rangrej
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Dear Somnath, here is the answer that I had promised. Your question shows up the trend these days to rush to commercial programs like ANSYS Fluent etc. You will see from my answer that we have NO need to solve the N-S equations at all here.
I am hoping to get the opinion of Oguz Emrah Turgut on my answer.
Just out of curiosity: Is this part of a masters thesis, an industrial consultancy work or any other?
Like I said earlier, if it is a shell and tube heat exchanger you are considering, your calculation will be infinitely more complicated. Better to leave it to a licensed software like that of HTRI.
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Want to model Flue gas which consist of H2O vapor, and it is getting condensed inside the tubes. How should I model it?
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it is a classic Stefan flow or Stefan diffusion problem, you can find it textbooks on combustion or chemical technology
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Heavy oil, extra heavy oil and Bitumen are natural resources with high-molecular weight and complex molecules. Proper measurement of critical properties is too difficult to measure and some times impossible. Thermodynamic description of such complex mixtures is greatly dependent on estimation and empirical correlations. I am looking for the best recommended procedures and protocols, as well as the suggested correlation for fluid characterization of heavy oil, extra heavy oil and bitumen.
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Please refer to following book to estimate such heavy products:
1) PVT and Phase Behavior of Petroleum Reservoir Fluids
Ali Danesh
2) Characterization and Properties of Petroleum Fractions
M.R. Riazi
As you stated above, properties estimation of these heavy products always has some time huge deviation from reality. An alternative procedure is to refer to experimental procedures by ASTM for example to estimate some transport and thermodynamic properties:
Volume 05.01 to 05.06 and 06.01 to 06.04
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Hello all,
I am looking for some texts which describes basic of phase field modelling (in specific reference to multi phase flows). 
I tried to look for some text-book regarding this but couldn't find it. Looking forward for kind reply in this regard.
Deewakar
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Dear Deewakar Sharma,
Below, some references about two-phase flows with phase-field modelling (or diffuse interface methods):
1) Book
Very complete book about phase-field/diffuse interface models for two-phase flow. But it focuses on the numerical method of Lattice Boltzmann methods.
If you do not work with LBM:
2) Topical review:
3) Binary fluids with Cahn-Hilliard equation (composition is the order parameter):
4) Water/Vapor and phase change (density is the order parameter)
Best regards
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I am using a single-component - two phase pseudo-potential LB model and need to compare my results. I, tried to compare my results with experimental data of falling of a water droplet into air which is a two-component physical system. I got good agreement with the experimental data. Computationally, I can argue that why my results are in a good agreement with the experimental data. However, I do not know if it is fundamentally true to model a two-component physical system by using a single-component numerical scheme ....
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In a single-component two-phase flow case (e.g., liquid water – water vapour), the pseudo-potential LB technique we are using is about the (spontaneous) phase separation as a result of the LB parameter values selected. In a two-component two-phase flow (e.g., water-air), the phase separation may be affected by the presence of the air – although you may argue that the gas phase (comprising water vapour and air) may be conceived as an ideal gas and that the air dissolved in the water may be ignored. Yet, the pressure in the water-air case is atmospheric, while at room temperature the single-component case is at the vapour pressure of the water.   
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Dear colleagues:
What are the basic equations that can be coupled to momentum, mass, ... etc equations in cases of the effect of electric and magnetic fields on bubble dynamics?
I wait your answers, and suggestions of earlier studies and articles.
Best Regards.
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Dear Khaled,
In case of electric and magnetic fields, the full magneto-fluid dynamics equations should be solved. This is basically achieved by coupling of Navier-Stocks momentum equation to Maxwell's equation (for electromagnetic fields). 
In case that the surfaces are charged, other equations should be used to account for change of electric-potential field and its effect on mass and momentum transfer. In which case Poisson-Boltzmann equations should be solved as well.
Hope this helps. 
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Hi.,
iam using particle tracking in fluent for a multi phase flow problem(in Unsteady State). I have injected some particles from inlet. So, if they touch the boundaries, they will be trapped and some are escaped. I have to plot a graph between the "particle capture fraction(%)on y-axis and time after the first particle enters the liquid pool on x-axis". Please help me in this .
Regards, Krishna
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Hi every one !
While using CFD codes ( Fluent 16 ) what should be the best practice for the following ?
Suppose a vertical rectangular bubble column( 30*60*6 = X,Y,Z cm ) , Single inlet at bottom with dimension 3mm*1.5mm , Velocity at inlet supposed to 0.06 m/s.
1) Velocity Inlet Boundary Conditions.. And also the Wall conditions ?
2) What should be the outflow ? Pressure Out or Degassing ?
3) Population Balance Models, How to treat this models ? i.e, BINS(CLasses) , Exponent Rato, Minimun Dia of Air ? what should be the boundary values of bins fractions if Inlet air dia is supposed to 8mm.
4) In the momentum Equation, how many forces can we include for overall best phenomenon ? Added mass, Drag, Lift, Wall Lubrication, Turbulent Dispersion, Turbulent Interaction, Surface Tension ?
5) For INITIALIZE... what should be the important changes ?
There are so many other factors that any expert can suggest to emphasis. 
Please suggest..
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Thank you Doctor,
Ricardo Vicente de Paula Rezende,
I am reading these papers....
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I am solving a multi-phase problem in Fluent. I want to define my secondary phase as the granular solid phase. I can see that in the dropdown menu of the secondary phase, only fluid materials are listed which I have already defined. Can someone help me with how to make the secondary phase solid?
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Hardik Mistry , True what were u are saying is correct.
But, since there are separate governing equations of each phase and the properties defines each phase. If you create a fluid with the properties of the solid (all properties which the software asks for) it should work, as these properties along with the volume fraction makes the difference in the equations solved.
Another option is to model using DPM multi phase models.
Thanks &Regards,
Rajesh.