Hi Serkan,
Thanks for a quick reply. I have followed the instruction and it still does not seem to work. I have got the .pvd file and also the folder and they are both in the same directory. But when I drag the .pvd file into Paraview, it still does not combine all the fieldname.
Here is the .vtu file I have exported from COMSOL (Untitled.vtu - Google Drive), I cant do an animation with this type of export.