[GBarraza]

Hi everyone!

This is my very first post in the forum! I hope you can help me out with the problem I'm facing at the moment. (If my post is not in the correct forum channel, let me know )

NOTE: If you are not really interested on the explanation, at the bottom is the real question

I am writing a functionObject which adapts (no refinement) the first layer cell thickness at runtime given a target y+ value. For this I impose a displacement on the first layer cells based on a ratio, and solving the cell displacement based on a custom equation.

Currently, I have achieved to displace the first cell successfully, and adapting the rest of the cells in the far field with a smoothing algorithm. However, when I displace the cells towards the wall, the edges which originally were normal to the wall become a bit tilted. The problem is when the fist cell really close to the wall, since a small bit of distortion causes a big non-orthogonality on those cells, making my simulation crash.

To this end, I implemented an edge correction for the first layer of cells which guarantees that the edges of the layer remain normal to the wall. But, then the layers above get distorted.

Question: Is there a straightforward way to get the edges above (e.g. the next 5 layers), or keep the edges aligned?

I have tried looking in the SnappyLayerDriver.C to come up with an analogy, but no success so far.

I attach an image so the problem is better understood.

Thanks in advance!!!
Guillermo

[Fann]

Hi GBarraza，

I'm sorry I don't have the ability to answer your question, but I have a question similar to yours. I want to know, can you modify the grid points by judging the speed in the grid points？ for example, when the speed reaches a certain value, Increase the position of the grid point in the z direction.
I would be very grateful if you could answer me.
Best wishs for you!
Fann

[GBarraza]

Hi Fann,

with regards to your question :

Originally Posted by Fann

I want to know, can you modify the grid points by judging the speed in the grid points？ for example, when the speed reaches a certain value, Increase the position of the grid point in the z direction.
Fann

If you already have the interpolated field on the nodes (e.g. a volScalarField like U into a pointScalarField), then you can move an specific mesh point based on the metric field you defined (and with the moving mechanism/criteria you want to apply)

I'll leave you an example:

//Interpolation of velocity field U
const volVectorField& U = mesh_.lookupObject<const volVectorField>("U");
interpolationCellPoint<vector> UInterp(U);


//Reference to mesh points field
pointField& points = mesh_.points();

//Probably you iterate over boundaries, cell points, etc...
//Example iterating over every cell's points
forAll(cellPointLabels, pointI)
{
    if (mag(UInterp[pointI]) > 10.0)
    {
        //Displacing your point by one unit in the z-direction
        points[pointI] = points[pointI] + vector(0,0,1)
    }
}

//Move the points
mesh_.movePoints(points);

;

I hope that helps you.

Guillermo

[GBarraza]

Originally Posted by GBarraza

Question: Is there a straightforward way to get the edges above (e.g. the next 5 layers), or keep the edges aligned?

I have already found my way to solve the problem. Thanks anyway!

[HPE]

Hi

- Is it possible to elaborate how you had managed to solve the issue, if possible?

Many thanks.

[GBarraza]

Sure,

As for how I managed to get the off-plane edges of the layers above the first I:

1. iterate over all patch faces, get the cell corresponding to the face and the opposing face of the boundary face.
2. Iterate over all edges of each cell and get those which are not contained neither in the boundary face nor in its opposing face.
3. Use faceOwner (or faceNeighbour) to get the cell at the other side of the opposing face.
4. Repeat the procedure for all the layers wanted.

Important to notice, it has the assumption that all the cells on the boundary are hex (or boundary layer cells).

To keep the edges aligned, I simply did a vector projection from the edges of the new mesh into the edges of the old one.

I hope it helps of something.

Guillermo