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July 30, 2001, 07:27 
CREATING A VERTICAL CIRCULAR PIPE

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


July 30, 2001, 07:42 
Re: CREATING A VERTICAL CIRCULAR PIPE

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For 3D cartesian calculations, you should create a "Ogrid patched to Hgrid" manual page 334. Extrude this surface to create a solid. Then you have your geometry. Jan


July 30, 2001, 08:12 
Re: CREATING A VERTICAL 2D PIPE

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


July 30, 2001, 09:06 
Re: CREATING A VERTICAL 2D PIPE

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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 

July 30, 2001, 09:50 
Re: gassolid flow in horizontal pipe

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Hi, I'm trying to solve the gassolid 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.


July 31, 2001, 03:11 
Re: CREATING A VERTICAL 2D PIPE

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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 yaxes to the xaxes 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. 

July 31, 2001, 03:58 
Re: CREATING A VERTICAL 2D PIPE

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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 

July 31, 2001, 05:59 
Re: CREATING A VERTICAL 2D PIPE

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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


July 31, 2001, 08:01 
Re: CREATING A VERTICAL 2D PIPE

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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 

August 1, 2001, 03:14 
Re: CREATING A VERTICAL 2D PIPE

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Thanks Jan for your patience.
I want to simulate gassolid flow through a vertical pipe.Initially I want to calculate the fluid flow field,then go for calculation for the gassolid phase. The flow could be downward or upward. I did these calculations quite easily using FLUENT.There I changed the direction and coordinate 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 gassolid 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. 

August 1, 2001, 03:25 
Re: CREATING A VERTICAL 2D PIPE

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


August 1, 2001, 03:45 
Re: CREATING A VERTICAL 2D PIPE

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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 twophase flow by langrangian and by eulerian models and send them to your email. Why do you want to calculate the flow with both models, Is it dense or dilute flow? Jan 

August 1, 2001, 08:20 
Re: CREATING A VERTICAL 2D PIPE

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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 gassolid 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 EulerianEulerian 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. 

August 1, 2001, 08:23 
Re: CREATING A VERTICAL 2D PIPE

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


August 1, 2001, 10:56 
Re: CREATING A VERTICAL 2D PIPE

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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 eulereuler 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 twophase flow is difficult to simulate (easy to obtain a solution though) Jan 

August 2, 2001, 06:11 
Re: CREATING A VERTICAL 2D PIPE

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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 particlewall collision.Turbulentparticle 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 EulerEuler 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. 

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