In one of my analysis recently, I found the vorticity map always has some patterns along the 45 degree (or 135 degree), like in the image attached. But the particle movement in my video are almost random, and there cannot be any preferences along the specific 45 degree. I guess this might be related to the way the data is averaged and interpolated, but I don't know how. Can anyone help me solve this puzzle?
Re: Why are the patterns always along the 45 degree
Thank you so much for your reply!! But I found the situation does not change much. Actually when I draw the contour plot by myself and without resizing the colormap, there are still some patterns along the 45 degree, as in the figure below. So I think this is related to the calculated vorticity data itself. Is that possible that the algorithm in PIV might cause this?
I don't think that this looks unnatural... You have data points in a cartesian coordinate system, and drawing contours around similar values. There will always be horizontal, vertical and diagonal connections, and this is what I see...
The vorticity in PIVlab is calculated by the Matlab built-in function "curl". Maybe you can check that out.