Hi, I'm using CFX 4.3.I want to model a vertical pipe of circular cross-section.But I don't find any example in the manual to do it.Can anyone help me out? Regards,sanjib.

For 3D cartesian calculations, you should create a "O-grid patched to H-grid" manual page 3-34. Extrude this surface to create a solid. Then you have your geometry. Jan

Thanks Jan.How do I do the same in 2d,axisymmetric case? Regards, Sanjib.

Search this forum, it has been posted before, or read the online help under the analysis form in build, about creating different geometries. 3D cylindrical, 3D cartesian, 2D axisymmetric pipes. Hope it helps.

Jan

Hi, I'm trying to solve the gas-solid flow in a horizontal pipe.I'm using CFX 4.3.I have tried to follow the example but could not do it.The main problem is coming in settieng the proper particle density.Can anyone suggest any solution? Regards, Sanjib.

Hi Jan, Is it possible to convert a horizontal pipe into a vertical pipe?In FLUENT I was able to do that by changing the gravitational constant from the y-axes to the x-axes and changing the sign ,positive or negative,for upward or downward flow.Is there any such feature in CFX4.3?Or do I have to build a vertical pipe in CFX_BUILD?I searched through the manual but they didn't explain these points.Moreover, how to build a vertical cylindrical pipe in 2d?I have solved the problem at hand for a horizontal pipe,but cannot do it for a vertical pipe.Please give me some idea.

Regards, Sanjib.

Dear Sanjib,

I have allready answered that question in another of your post about Bouyancy . It is just as easy in CFX as in fluent, you just change the gravitation vector. Jan

Hi Jan, I've tried that out,but it is giving an error message saying that BUOYANT,INCOMPRESSIBLE FLOW HAS BEEN SPECIFIED WITHOUT HEAT OR MASS FRACTION EQUATIONS FOR SINGLE PHASE FLOW.I didn't get this sort of message in FLUENT.There the change of the gravity vector was enough.The manual also doesn't say anything in this reagard.Can you please suggest any other way out? Thanks, Sanjib

If you are calculating an incompressible, isothermal single phase flow you dont need the gravity.

Please Sanjib explain what you are want to calculate, it would be an help.

I know it is a pipe (upward) and possible with solid particles which you want to calculate as eulerian or Lagrangian???

Jan

Thanks Jan for your patience.

I want to simulate gas-solid flow through a vertical pipe.Initially I want to calculate the fluid flow field,then go for calculation for the gas-solid phase. The flow could be downward or upward.

I did these calculations quite easily using FLUENT.There I changed the direction and co-ordinate of the gravity( y->x ) to convert the horizontal axisymmetric pipe into vertical pipe with inlet either at the top or bottom according to the sign of the gravity.But in CFX 4.3 I don't find any such option.

I want to simulate the gas-solid flow both for the Lagrangian as well as for the Eulerian case.Also I want multiple entry points at the boundary wall.Can you suggest how to do these?

I appreciate your understanding and help.

Regards, Sanjib.

I'm sure you can change the gravity field in CFX quite easily!(do a search for "gravity" in the manual).

Dear Sanjib,

I have explained the use of the gravity field in another reply to you.

I will find some of my old command files, solving particulate two-phase flow by langrangian and by eulerian models and send them to your e-mail.

Why do you want to calculate the flow with both models, Is it dense or dilute flow?

Jan

Dear Jan,

Thanks for your help.

As I am still learning the software so it is better to solve both the cases.Moreover I had solved gas-solid flow with Lagrangian tracking with FLUENT.Here I want to check whether this software also gives almost the same results. As far as as the dense phase is concerened,CFX4.3 has the Eulerian-Eulerian calculation but FLUENT doesn't have such a feature.My actual project will depend upon how reliably I can get the results from these softwares. I have experimental results with me and also some numerically simulated data published previously.If the results are not reliable then I'll have no other option but to go for writting my own code.Already I have started and achieved good results for single phase flows.But the actual system is far more complicated so I'm trying to avoid it as far as possible.

Anyway,thanks for your reply. Sanjib.

Dear Herve, Have you solved any such case?Please give me some more information about it. Regards, Sanjib.

Dear Sanjib,

It is easy to obtain a numerical solution, even a correct numerical solution!

Be carefull to check if you solve it correct, The euler-euler might not be the best solution if you only have a small fraction of particles, vice versa for the lagrangian. What size are your particles and variance, what is the density, form, etc, does turbulent dispersion have an effect, additional forces etc...

Be sure to consider everything. Particulate two-phase flow is difficult to simulate (easy to obtain a solution though)

Jan

Dear Jan, I have surveyed quite a few papers on each of the topics that you have mentioned.At present I am involved in including the right model for the particle-wall collision.Turbulent-particle interaction is definitely going to be a part of my numerical simulation.Initially I'm doing the simulation for the Lagrangian case.That helps to understand the basic physics and physical factors behind the particle trajectory.However from the practical standpoint the Euler-Euler method has to be considered as the number of particles is going to be large. It seems you have quite a lot experience in this area,so your suggestions will be invaluable to me.

Thanks for your patience and interest, Sanjib.