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firavia November 8, 2012 19:24

weird velocity profile
2 Attachment(s)
hello I have been trying to do a CFD simulation on a venturi pipe using RNG k epsillon method, the solution converged but when I took a plane to check the velocity profile on it I found out that in the middle of the section plane the velocity is low and on the sides near the wall the velocity get high thn it come close to zero near on the wall.

I have attached an image for the simulation , I just want to know if this is normal or not .
flow rate is :387 kg/s. fluid is water. inlet diameter is 0.8m , diameter of the pipe after the constriction is 0.4m. the section plane was taken in the constricted area.
Please find attached 2 images showing the velocity profile and the geometry of my case.

firavia November 8, 2012 22:01

can anyone help please ?

Far November 9, 2012 00:10

This is not normal!!! What is the boundary condition on wall : slip or no slip?

firavia November 9, 2012 05:24

1 Attachment(s)
No slip conditions, and I have another plan section that might help identify the problem please check it , it is attached below. Do you think it is a mesh problem ? I set the solution monitor to 1e-3 for k epsilon velocities and momentum.

Far November 9, 2012 05:39

reduce convergence criteria to 1e-5 and run for longer time and then see... Would you describe your problem in detail?

firavia November 9, 2012 06:42

it is a venturi pipe with water flowing at 387 kg/s thats all, it is very simple and straight forward althoug I was surprised of the velocity profile that I have got , I knew it is unusual . I am trying to work on the mesh at the moment and see if it changes something, it looks like I have got a separation of flow in this case. it is weird !

Far November 9, 2012 07:09

can you share the mesh and case file so that I can check it by running it on my computer.

firavia November 9, 2012 07:14

ok that would be great
can you give me your email so that I send it to you please.

Far November 9, 2012 07:15

just look at the left and you will find the email id

firavia November 9, 2012 07:30

Hello, the files are big and they cannot be uploaded to gmail, so I will upload them on my website and send u the link with the password to your E-mail, thank you for your help

Far November 9, 2012 07:32

you can upload it to dropbox.

firavia November 9, 2012 07:33

I am sorry I am already uploading it to my website, it is the same thing, I dont have an account with dropbox. it is very easy to download it from the webste, just right click on the file name and download it , i have uplaoded 2 files with .rar extention.

firavia November 9, 2012 07:54

Hello, I sent you the link , thank you very muich

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