Merging pvd data depends your application. If you have two files, assuming that both pvd files have the same points (xy coordinates), you can merge the attributes V, Pres, using the AppendAttributes Filter see also here
Merging pvd data depends your application. If you have two files, assuming that both pvd files have the same points (xy coordinates), you can merge the attributes V, Pres, using the AppendAttributes Filter see also here