Basically, I have a hexahedral finite element mesh. I know the coordinates of elements, I used the coordinate transformation into an isoparametric structure and shape(basis) functions to calculate the Jacobian to find the volume.
I also need the surface area of each face separately along with its outward unit normal.
What would be the best possible way to do that? Can the Jacobian be used to do this?
I have tried working with using vector algebra, by finding the cross-product of diagonals of each face to find the direction of the outward unit normal and the area but that doesn't work for an irregular hexahedron( which I think shouldn't be the case). Can this be another general approach?
I can't understand where I am going wrong here. Will be grateful if someone can give me some idea.