[sasanghomi]

Dear Friends ,

I am using dynamicMesh for engine simulation . I update the mesh manually and after remeshing I should map the latestTime of previous mesh on the new geometry (Actually new mesh ). The problem is that after each mapping I have got a big change in velocity field . Please take a look at the attached picture . In this picture you can see the variation of radial velocity versus time in a specific point in the engine . There are some big changes in the values of radial velocity (in the plot) . These big changes occur after each mapping (exactly) . Actually after each mapping velocity field is not coincide with previous time step in the previous mesh.
Please anybody help me for getting the reason of these big changes (rapid variation) . And How can I solve this problem ?

I appreciate any help from you
Thanks and best regards
Sasan.

P.S. I highlighted the big variations in the picture .

[mturcios777]

Can you post a picture from ParaFoam with the velocity field from the old and new meshes? Also, are you mapping consistently or otherwise?

[sasanghomi]

Dear Marco
Thank you very much for your reply
I used consistent mapping. I attached two pictures that they are after and before mapping . I think they are ok. But I don't know why there are some rapid variations in data that comes from swak4Foam.

Any Idea?

Best regards
Sasan

P.S. these pictures are not in the same time there is a little difference between time of them and difference in velocities in paraFoam comes from there

[mturcios777]

The interpolated fields look similar enough. I would check the discrete fields though, as interpolations smooths and tends to hide details that could be important.

Also, I'm not sure if its a problem with my web browser, but the engine seems to change diameter and the piston seems to move. It may be possible that the image is getting squished to fit as the aspect ratio may be different. In following with this, I would do a checkMesh on both meshes 1) to check the quality and 2) to compare the total mesh volume and dimensions.

Finally, how is swak4Foam calculating the radial velocity? Curious there may be something there worth noting.

[sasanghomi]

the time of two pictures is a little different and that's why the piston has moved in the second picture.
About swak4Foam I should say that I wrote a function . I think this function is correct for any point on the axis of cylinder .And it can calculate radial velocity.

Take a look at this :

radialvelocity
    {
        type            swakExpression;
      expression     "(U.x*cos(teta))+(U.y*sin(teta))" ;
   variables "teta=atan((U.y)/(U.x));"    
functionObjectLibs ("libsampling.so");
         accumulations (
            average
        );
    //valueType    internalField;
         valueType set;
         setName   data;
        enabled         true;
        outputControl   outputTime;//timeStep;
        outputInterval  1;

     set {
            type cloud;
            axis z;
            points (

                (0 0.00000001 -0.005)

            );
        }
        
    }

Do you think is there any problem in this function?

P.S. the origin coordinate is in the center of cylinderHead.