initial velocity field with a pressure difference

sven82 · July 23, 2009, 05:20

hi,

Im not really sure about my initial fields, and i hope everyone help me with this problem.
first of all I create a simple geometries.
For the next step I will initial my p and U fields
.
The problem now my velocity field is define by a pressure difference .

The question is that the correct definition, for this problem?

/************************************** p *************/
outlet
{
type fixedValue;
value uniform -50000;
}
inlet
{
type zeroGradient;
}
.
.
.
/************************************************** ***/

/************************************** U *************/
outlet
{
type zeroGradient;
}
inlet
{
type zeroGradient;
}
.
.
.
/************************************************** ***/

Schag · July 23, 2009, 05:59

Hi,

I think there is something missing here.
If you want your flow to be defined by a pressure difference, you have to put fixedValue to outlet AND inlet, otherwise your domain is going to have a uniform relative pressure equal to -50000, and in theory no velocity...

For further precision, we'll need explanations on geometry, solver used...

kjetil · July 23, 2009, 06:05

Also, this seems to be the boundary condition - not actually the initial field? The initial condition can be set in the internalField, located above you boundaryField. For example internalField uniform <your-number>; .

July 23, 2009, 05:20	initial velocity field with a pressure difference	#1
sven82 Member Sven Degner Join Date: Mar 2009 Location: Zürich Posts: 55 Rep Power: 17	hi, Im not really sure about my initial fields, and i hope everyone help me with this problem. first of all I create a simple geometries. For the next step I will initial my p and U fields . The problem now my velocity field is define by a pressure difference . The question is that the correct definition, for this problem? /************************************ p *********/ outlet { type fixedValue; value uniform -50000; } inlet { type zeroGradient; } . . . /********************************************** / /*********************************** U *********/ outlet { type zeroGradient; } inlet { type zeroGradient; } . . . /********************************************** */

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July 23, 2009, 05:59		#2
Schag Member Julien Schaguene Join Date: Apr 2009 Location: France Posts: 55 Rep Power: 17	Hi, I think there is something missing here. If you want your flow to be defined by a pressure difference, you have to put fixedValue to outlet AND inlet, otherwise your domain is going to have a uniform relative pressure equal to -50000, and in theory no velocity... For further precision, we'll need explanations on geometry, solver used...

July 23, 2009, 06:05		#3
kjetil Senior Member Join Date: Mar 2009 Location: Norway Posts: 138 Rep Power: 17	Also, this seems to be the boundary condition - not actually the initial field? The initial condition can be set in the internalField, located above you boundaryField. For example internalField uniform <your-number>; .