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-   -   Problem with timeVaryingUniformFixedValue (http://www.cfd-online.com/Forums/openfoam/67230-problem-timevaryinguniformfixedvalue.html)

anon_c August 8, 2009 05:16

Problem with timeVaryingUniformFixedValue
 
i modified the Cavity problem with a moving wall with u=u(t)


in the dictionary 0 there is the initeal of U

there:



/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.5 |
| \\ / A nd | Web: http://www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
movingWall
{
type timeVaryingUniformFixedValue;
fileName "ramp";
outOfBounds clamps;
}

fixedWalls
{
type fixedValue;
value uniform (0 0 0);
}

frontAndBack
{
type empty;
}
}

// ************************************************** *********************** //


in the ramp data

(
(0.0 (1 0 0))
(5.0 (10 0 0))
(5.00001 (0.001 0 0))
)

that means after 5s the velocity u of the wall stops





the problem is

that form t=0s till t=5s the wall velocity is groing that is good and the velocity field simes to be well but after that after t=5s when the wall velocity stops

the holleeee velocity field go to zero????? that is not normal it have to slow down

sega August 8, 2009 06:57

What is your next written timestep after the 5th second?

Maybe your fluid is viscous enought so it allready settled down back to zero velocity in this time period?

You can try to decrease the timestep after the 5th second, or increase the fluid viscosity.

anon_c August 8, 2009 07:07

hello sega

as you can se the ramp data is

(
(0.0 (1 0 0))
(5.0 (10 0 0))
(5.00001 (0.001 0 0))
)

that means from 5 to 5.00001 from 10m/s to 0.001m/s

and i donnt think that water is so viscos to get a zero velocity field???? i am really not shure what is going on there

and the same problem if i do

that means from 5 to 5.00001 from 10m/s to 0m/s

so i have no idea

sega August 8, 2009 07:14

Thats not what I am talking about.
Are you writing a timestep directory at 5.00001 or at a later time?
Meaning at which timestep are you investigating a zero velocity field?

anon_c August 8, 2009 07:20

i get the zero velocity field

5.25s

is it by zero

and the transport modell


/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.5 |
| \\ / A nd | Web: http://www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object transportProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

nu nu [0 2 -1 0 0 0 0] 0.01;

// ************************************************** *********************** //

sega August 8, 2009 08:29

Maybe you can investigate the results at a timestep inbetween 5 and 5.25.

anon_c August 8, 2009 08:57

hello sega


i just try it agian

at the time step of 5.1s the wall is zero and the field in the box is not zero :) , i think that is what you means it was to fast and the velocity field is zero (die viskositšt ist wharschinlich so hoch gewessen das es sofort dann abgeklungen ist)


thank you very much that menas i now cann start wall velocity that is time dependent

:)

sega August 8, 2009 09:03

Yes! Thats what I meant. :)

Now have fun with all the upcoming simulations and don't hesitate to ask.


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