Gradient of tensor components

Hello,
I have an unstructured dataset with a vector field defined on it (vorticity). I generated the gradient tensor and I know that the components are given as a tuple from 0 to 8 as dw1/dx, dw1/dy, dw1/dz, dw2/dx… dw3/dz. Now I need to compute the laplacian of that field, so I need the second derivatives; I used the gradient filter again and as expected I got 27 components. Does anybody know how they’re ordered?

FYI @Francois_Mazen