[zhajingjing]

I want to improve my postprocessing tool for my wave tank to make it suitable for a wave tank with non-uniform mesh.In order to get the average value of a field with non-uniform mesh,I have to calculate the size of each cell (the heigt,length,width of a rectangular cell) as a weight factor,but I don't know how to get this kind of geomertric information of a cell.
One method is to get the coordinate value of the vertices of a cell,then make one subtract another.But I
can't go on at the detail.

 
  forAll(mesh.cellCentres,cellid)
    { 
 
        if(abs(mesh.cellCentres[cellid].x()-x)<=deltaX/2)  //deltaX:the length of a cell, choose out the cells at the x point along the 2D wave tank
 
       {
         ncells++;
         sumField+=field[cellid]*deltaY;//deltaY: the height of a cell
        weight+=deltaY;
 
        Info<<ncells<<"cell No"<< cellid <<"field value"<<field[cellid]<<endl;
       }                        
 
    }   
 
  sumField=sumField/weight;  //the average value of the gamma field at the x point along the wave tank

The question is , how to calculate the deltaX,deltaY according to the cellid that has been chosen out.

in the following short script:

const labelList patchCells = this->patch().faceCells();
const fvPatchScalarField& gamma=patch().lookupPatchField<volScalarField,scalar >("gamma");
const pointField& points = mesh.points();
forAll(patchCells,i)
{
 labelList cellpoints=mesh.cellPoints(patchCells[i]);
 label size=cellpoints.size();
 for(int j=0,j<size,j++)    //???如何读取单元尺寸
 {    
  points[cellpoints[j]].y()
 
 ...
 gamma[patchCells[i]]*...
    waveAtWavemaker_=...
｝

I know something about how to access the coordinate value of a vertex of a cell,but I don't know how to access two vertices at the same time, if I could, of course I will get the height of a cell(2D)

Is there anyone can help me?Thanks


two attachments: the old version of the wave tank postprocessing tool,
and another is a new version waiting to be improved to postprocess the non-uniform mesh wave tank.

[richpaj]

isn't it possible to simply use gAverage (volume averaging)?


Richard

[Daniel73]

Hey guys,
Do you know how i can find the deltaX, deltaY and deltaZ of a cell?
I can use some thing like "scalar dx = mesh.C()[0].x() * 2.;" for serial, but for parallel case it needs many considerations...
So do you know any simple function?

[safre]

Did you get an answer to get dx, dy and dz?

[elmo555]

Hey guys,

Originally Posted by Daniel73

Hey guys,
Do you know how i can find the deltaX, deltaY and deltaZ of a cell?
I can use some thing like "scalar dx = mesh.C()[0].x() * 2.;" for serial, but for parallel case it needs many considerations...
So do you know any simple function?

Originally Posted by safre

Did you get an answer to get dx, dy and dz?

Not sure if you're still interested in this (your question is from 2014), but this is how you can get the distances between cells:

mesh.delta()

It returns cell distances for each face as surfaceVectorField and is implemented as:

forAll(owner, facei)

 {
 delta[facei] = C[neighbour[facei]] - C[owner[facei]];
 }

in fvMeshGeometry.C

[Taataa]

In case someone was looking for a complete answer, here is the code to get the deltas in each direction for each cell:

const surfaceVectorField& deltas = mesh().delta();
forAll(deltas, I)
{
    Info<<  "dx[" << I << "] = " << deltas[I].x() <<endl;
    Info<<  "dy[" << I << "] = " << deltas[I].y() <<endl;
}

[Alisa_W]

Hello,

I am focusing on the definition of deltax, deltay and deltaz in OF. I am so happy to see your answer and it really give me some ideas! However I still have some problems.

Does it mean that when I want to use deltax(or deltay, etc) in a piece of code, I just need define "deltas" first (like your code "const surfaceVectorField& deltas = mesh().delta(); ") and use deltas[I].x() in loops?

Another puzzle is what x, y, z represent. Does x, y, z here represent three directions in Cartesian coordinates? However, in fluid mechanics, x,y,z represent streamwise direction, normal direction and spanwise direction. A typical physical quantity is y+(yplus).

Thanks a lot! Anyone who can give me some suggestions is welome!

Alisa.

Originally Posted by Taataa

In case someone was looking for a complete answer, here is the code to get the deltas in each direction for each cell:

const surfaceVectorField& deltas = mesh().delta();
forAll(deltas, I)
{
    Info<<  "dx[" << I << "] = " << deltas[I].x() <<endl;
    Info<<  "dy[" << I << "] = " << deltas[I].y() <<endl;
}

[Taataa]

Here is how delta is defined in OF:

forAll(owner, facei)
{
    delta[facei] = C[neighbour[facei]] - C[owner[facei]];
}

So essentially, delta for each face is the distance between the centers of its neighbor and owner cells. If that's what do you want in your code then yes, you can use that.

[Alisa_W]

What I want is xyz in dynamic mechanics level. However, your idea makes me understand OF frame more clearly. Thank you!

Originally Posted by Taataa

Here is how delta is defined in OF:

forAll(owner, facei)
{
    delta[facei] = C[neighbour[facei]] - C[owner[facei]];
}

So essentially, delta for each face is the distance between the centers of its neighbor and owner cells. If that's what do you want in your code then yes, you can use that.

[shiyu]

Originally Posted by Alisa_W

What I want is xyz in dynamic mechanics level. However, your idea makes me understand OF frame more clearly. Thank you!

Hi Wang,

I am wondering if you have found a better solution of x,y,z lengths in every cell, instead of the delta distance between every two cells.

Thanks

BR,
Shiyu

[CFDanielGER]

Hello everybody,


am I right that this code give you the deltas in x, y and z for every cell, I mean the dimensions of each cell or is it the distance between two cell center points?

Originally Posted by Taataa

Here is how delta is defined in OF:

forAll(owner, facei)
{
    delta[facei] = C[neighbour[facei]] - C[owner[facei]];
}

So essentially, delta for each face is the distance between the centers of its neighbor and owner cells. If that's what do you want in your code then yes, you can use that.

Is there maybe a more efficient way than using a forAll loop? I guess this may be rather time consuming for large meshes?


Many thanks for your help!