[amtri]

Hello,


I have a couple of results files that I am unable to clearly understand. In one of them I see a boundary condition defined as follows:

type uniformFixedValue;
uniformValue tableFile;
uniformValueCoeffs
{

file "ramp";
}

Another boundary condition is defined as


type uniformFixedValue;
uniformValue tableFile;
uniformValueCoeffs
{
file "ramp";
}
value uniform -0.002893859;



The only difference between the two entries is the "value" entry. This happens to be a scalar value. But suppose this were a vector value. What should the contents of the file "ramp" contain? A vector per entry? Or a scalar per entry that is simply used to scale a value as a function of time?


I ask because the second boundary condition has a "value" defined. If the quantity were a vector, I imagine the "value" would have 3 components if I were to use the contents of "ramp" to scale the quantities as a function of time. But "value" is not present in the first case. So if "ramp" contains scaling values for time, what would be the 3 components to be scaled?


Thanks. I would be grateful for any help in clarifying this issue for me.

[RGS]

Originally Posted by amtri

Hello,


I have a couple of results files that I am unable to clearly understand. In one of them I see a boundary condition defined as follows:

type uniformFixedValue;
uniformValue tableFile;
uniformValueCoeffs
{

file "ramp";
}

Another boundary condition is defined as


type uniformFixedValue;
uniformValue tableFile;
uniformValueCoeffs
{
file "ramp";
}
value uniform -0.002893859;



The only difference between the two entries is the "value" entry. This happens to be a scalar value. But suppose this were a vector value. What should the contents of the file "ramp" contain? A vector per entry? Or a scalar per entry that is simply used to scale a value as a function of time?


I ask because the second boundary condition has a "value" defined. If the quantity were a vector, I imagine the "value" would have 3 components if I were to use the contents of "ramp" to scale the quantities as a function of time. But "value" is not present in the first case. So if "ramp" contains scaling values for time, what would be the 3 components to be scaled?


Thanks. I would be grateful for any help in clarifying this issue for me.

Hello,


The syntax for using this boundary condition (including how to use it for vectors and for ramping values over time) can be found here: https://www.openfoam.com/documentati...xed-value.html

As you can see, there are no uniformValueCoeffs or value entries for this boundary condition. Did you find this code in a case folder that runs without errors?


Cheers

[amtri]

Originally Posted by RGS

Hello,


The syntax for using this boundary condition (including how to use it for vectors and for ramping values over time) can be found here: https://www.openfoam.com/documentati...xed-value.html

As you can see, there are no uniformValueCoeffs or value entries for this boundary condition. Did you find this code in a case folder that runs without errors?


Cheers

Hi RGS,


Thanks for the reply.


Yes; the folder has results for several time steps. Unfortunately, I am focused on the syntax of the files - which is why people come to me on this. But I'm no expert in running OpenFOAM.


I should have access to a Ubuntu machine in a few days. I can install OpenFOAM there - much easier than on Windows.


Interestingly enough, there is no time step 0; I guess it's the first time I see that. The analysis start at 0.38. I don't see the "value" parameter at steps 0.38, but I see it in all subsequent steps. This leads me to believe that these subsequent steps were generated by OpenFOAM. They do appear to be machine formatted.


Are you aware of a file syntax verifier for OpenFOAM?


Thanks.

[Yann]

Hello Amtri,

uniformFixedValue is a boundary condition derived from one of the basic one. The "value" parameter is a placeholder inherited from this basic condition. It is read only at startup and might be used as an initial value if the boundary condition does not overwrite it right away.

Please check here : What is the difference between the parameters 'value' and 'p0' in totalPressure BC?

So there is basically no difference between the boundary condition definitions in your initial post.

The value defined in the file "ramp" or in the "value" parameter can be a scalar or a vector, depending on which variable it is applied to. (eg. it has to be a vector if it is used for the velocity, or a scalar if it is applied on the temperature)

I hope this helps,
Yann

[amtri]

Hi Yann,


Thanks so much for the clarification. I followed all the links you pointed me to. Apparently I wasn't the only one confused by this.


Thanks again!

[RMC1]

Hi Foamer, I need help urgently as I am a beginner in openFoam. I want to make a wall oscillate that should move in x direction.
Unfortunately I am missing the right BC for uniformFixedValue or codedFixedValue.

please help me urgently.