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-   -   !!!About setting the roughness constant (http://www.cfd-online.com/Forums/fluent/34250-about-setting-roughness-constant.html)

coma July 21, 2004 23:08

!!!About setting the roughness constant
 
hi ,i found it difficult to setting the roughness height and roughness constant when i am modeling the flow in pipe.the friction constant is f=0.0012,so how to deal with it ??? by the way i could not find Schlichting's book

leila July 24, 2004 03:44

Re: !!!About setting the roughness constant
 
hi, I did'nt get what u exactly mean by saying finding it difficult. but for activating roughness on your wall BC panel u should note that for laminar flow have a laminar sublayer which makes rooughness unimportant. so do as follows: go to define models viscous ana choose one of the three turbulent models of Spalart.. ,k-epsilon or k-omega and then if u go to BC panel and then u want to set wall BC on the Momentum panel which is now activated u'll find roughness hope this will help

coma July 24, 2004 07:46

Re: !!!About setting the roughness constant
 
wellúČI see what u mean ,but i am wondering how to determine the exact value of roughness constant and roughness height according to the boundary theory.sb can bring forward the experienced formula for us ??thanks

L.H.MIN July 26, 2004 09:48

Re: !!!About setting the roughness constant
 
Hi,

As far as I know, the roughness constant and roughness height in fluent is based on Nikurades's work for tubulent.

Please, look up text for Fluid Dynamics or Fluent Manual.

All books regarding tubulent flow inside tube have this content in itslelf.

Good luck.

aggie December 28, 2011 02:36

L.H.MIN ,

In Nikuradse's work, he mentions the friction factor as a function of pipe diameter and roughness height only for turbulent flow. So, is that friction factor the same thing with roughness constant in Fluent?

Thanks.


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