traction free bc

alinik · November 25, 2010, 14:36

Hi everyone

Does anybody know haw can I introduce "traction free" BC at the outlet of my domain in CFX?

Regards

ghorrocks · November 25, 2010, 17:36

What is a traction free BC?

alinik · November 25, 2010, 23:18

this relation is called "traction"

T=-pI+2*mu*D,D=0.5*[grad(u)+grad(u)^T]

whenever it equals to zero, there is no traction or we can say it is traction free

alinik · November 25, 2010, 23:18

by the way "mu" is viscosity of the fluid

ghorrocks · November 27, 2010, 05:34

I assume u is the velocity field. What is p and I?

Can you explain what is the physical significance of this?

alinik · November 27, 2010, 07:03

P is pressure and I is the Identical matrix. it is said that this kind of bc does not affect the upstream flow conditions significantly

ghorrocks · November 27, 2010, 08:02

I see.

You may be able to do it as a CEL function on an outlet boundary condition with a CEL specified velocity or pressure, but you probably have to implement it in fortran.

November 25, 2010, 14:36	traction free bc	#1
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 18	Hi everyone Does anybody know haw can I introduce "traction free" BC at the outlet of my domain in CFX? Regards

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What does "traction free" mean?	Yang	Main CFD Forum	13	August 3, 2021 06:39
Can Flow-3D plot the free surface area in Iso-surface or colour variable?	therockyy	FLOW-3D	1	June 20, 2010 20:36
free RANS code with free surface ability	Lou jing	Main CFD Forum	1	July 11, 2003 15:43
CFX 4.4 New free surface option	Viatcheslav Anissimov	CFX	0	April 3, 2002 07:27
Variable Density - Free Surface with FIDAP	Vitaliy Pavlyk	FLUENT	7	May 2, 2000 16:56

November 25, 2010, 17:36		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	What is a traction free BC?

November 25, 2010, 23:18		#3
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 18	this relation is called "traction" T=-pI+2muD,D=0.5*[grad(u)+grad(u)^T] whenever it equals to zero, there is no traction or we can say it is traction free

November 27, 2010, 05:34		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	I assume u is the velocity field. What is p and I? Can you explain what is the physical significance of this?

November 27, 2010, 07:03		#6
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 18	P is pressure and I is the Identical matrix. it is said that this kind of bc does not affect the upstream flow conditions significantly

November 27, 2010, 08:02		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	I see. You may be able to do it as a CEL function on an outlet boundary condition with a CEL specified velocity or pressure, but you probably have to implement it in fortran.