Science topic

# Multi Phase Flows - Science topic

Singular limits-interfaces-existence theory

Questions related to Multi Phase Flows

hi everybody i'm work on PDF based description of particles-laden turbulent flow. does this subjet interest any body her ?

I need to define mass transfer in two-phase mixture of nanofluid.

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?

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?

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

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,

in the small diameters (or depth for rectangular one) the trickle flow can't be exist. am I right? what is the threshold?

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???

May someone help in understanding the difference between phase-field method and level-set method?

Thank You

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?

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

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?

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?

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.

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.

I want to model CO2 multi phase flow inside ejector .Please help me in this reards.

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

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.

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

what is the distinction between these two flows?

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?

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

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.

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:

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

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?

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?

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 ?

Please suggest the latest topics on multi-phase systems (especially on transmission lines with more than 3-phase) to start my research work.

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.

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.

Why does the transverse length scale of turbulent flow have a negative region?

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.

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.

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.

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

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

Want to model Flue gas which consist of H2O vapor, and it is getting condensed inside the tubes. How should I model it?

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.

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

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 ....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.

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

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..

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?