Hi Fluent user, I am simulating a multiphase (air-water) system using DPM with water as a primary phase. Is that possible to set a free slip boundary between air and wall? I couldn't find the way to do it and currently my primary phase is set as 'no slip' boundary with the wall. Thanks in advance.

hi If u are using the fluent version 6.2 thr is an option in wall boundary condition which asks u to mention the specularity coefficient.It is through this option that u can specify the slip wall condition,The previous versions dont have it, In that case u would have to write an UDF to use the slip condition. u may ask the fluent experts as to how to set up the UDF in previous versions.

regards

Hi may your case was similar to my since i also have (air-water) flow in a pipe can you tell me please what did you mean by by DPM and are you used the VOF model to represent the phases and if you used it how can you represent them by it. Please tell me if you have the same of case we can cooperate together and about your question you can set the no slip boundary to the wall by un choosing moving wall in the wall BC. If you have some idea about my case you also can contact me by the email khalidb77@yahoo.co.uk. Sincerly Khalid

Thanks all for the reply, I'm thinking of using the two fluid model instead. Hi Khalid I've use VOF before for some flow in a stationary boundary but in my case now I'm not interested to know the fluid volume or fluid level, but I'm want to see the gas dispersion in mixing tank. I have some success to run the VOF before, in which I applied some pressurise air to remove water from the micropore. This is very straightforward actually. Cheers,

Thanks to the replay if you used the VOF model before can you assist me to how can i model a two phase flow in a pipe by using this model in which i want water be separated from air layer. Khalid

Dr Gimbun and Mr. Khalid , you cannot have free slip boundary condition in Fluent. You can specisy the shear rate to be zero at the wall and it may work like free slip but not the correct way to handle it. I am aware in CFX related journal article they do talk about free slip BC near the wall for pipe flows. They would also mention about wall forces. However you cannot alo have wall forces in Fluent even using UDF. Let me know what kind of pipe you guys are working on. Is it bubbly flow? KP

Hi Krishna, I know very well that we can set easily either no slip or free slip in CFX because I have try it some time ago. You are correct, in Fluent setting shear rate = 0 in Fluent didn't exactly similar with 'free slip' boundary condition. I'm not working on flow in pipe (like Khalid) I'm working on gas dispersion in stirred tank. I'm planning to do PBM on that later on. Thanks for a good discussion.

Dear Krishna :‎ I have no problem in my case to set free slip boundary , but I have a problem in represent ‎a two phase (air-water) flow using the VOF model into a pipe, can you guide me to how ‎can I did that please.‎ Thanks Khalid

I work on E-E. There we set sing define-phases so on and so forth. KP

Dear Krishna what did you mean by E-E are you work in single phase flow. Khalid

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