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Old   November 9, 2011, 02:07
Default Need help on Boundary Condition
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S Park
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Hello,
I'm still learning about OpenFoam, and I need some helps.
I want to model a converging flow, so there are two inlets coming in and
a single outlet.
However, instead of assigning velocity differences at inlets and outlets,
I want to make this a pressure-driven flow (thus assigning only pressure values and possibly assigning velocity values as zeroGradients) - and two inlets should have different initial pressure values.
So any suggestions for good boundary conditions for two inlets and an outlet?

Thank you in advance.
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Old   December 8, 2011, 18:27
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Quote:
Originally Posted by CNT9 View Post
Hello,
I'm still learning about OpenFoam, and I need some helps.
I want to model a converging flow, so there are two inlets coming in and
a single outlet.
However, instead of assigning velocity differences at inlets and outlets,
I want to make this a pressure-driven flow (thus assigning only pressure values and possibly assigning velocity values as zeroGradients) - and two inlets should have different initial pressure values.
So any suggestions for good boundary conditions for two inlets and an outlet?

Thank you in advance.
Try looking at

Pressureonly inlet BC

and

Pressure at inlet in OpenFoam

and then search the forum a little more for "pressure inlet"

I do remember that specifying pressure at the inlet, it is very easy to create hypersonic flow (not sure where I read that)...so be careful. Also, remember that if you use solvers like simpleFoam, the value you are specifying is actually pressure divided by fluid density.

Cheers,
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Old   April 26, 2012, 08:15
Default Need help boundary conditions using groovyBC
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Darwin
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Hi guys,

Im pretty new in OpenFoam (i m using Openfoam2.1). I consider the geometry of a cylinder and i would like to simulate a swirling turbulent flow (LES Simulation). I want to change the entry condition for the velocity field with the following expression: (i want a tangetial velocity profil which depends on radius)

" variables: Ur (radial velaocity), Ut (tangential velocity), r_vc (radius of the vortex), v_max (maximal velocity)

expression:
for 0 < radius < r_vc Ur = V_max * radius / r_vc

for r_vc < radius < R (radius of the cylinder) Ur = V_max *r_vc / radius"

Thanks in advance for your help !!
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Old   April 26, 2012, 09:42
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Quote:
Originally Posted by sundark28 View Post
Hi guys,

Im pretty new in OpenFoam (i m using Openfoam2.1). I consider the geometry of a cylinder and i would like to simulate a swirling turbulent flow (LES Simulation). I want to change the entry condition for the velocity field with the following expression: (i want a tangetial velocity profil which depends on radius)

" variables: Ur (radial velaocity), Ut (tangential velocity), r_vc (radius of the vortex), v_max (maximal velocity)

expression:
for 0 < radius < r_vc Ur = V_max * radius / r_vc

for r_vc < radius < R (radius of the cylinder) Ur = V_max *r_vc / radius"

Thanks in advance for your help !!

This is usually my go to answer on these, but why not try groovyBC (http://openfoamwiki.net/index.php/Contrib_groovyBC) or go ahead and install swak4foam (http://openfoamwiki.net/index.php/Contrib/swak4Foam) to get even more tools, and look at

groovyBC in openFOAM-2.0 for parabolic velocity bc

that will cover it for you. As always, use your search skills on the forum. Good luck.
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