My phd is in theoretical fluids and from a naval architecture (which is an engineering discipline) program. We fluids guys are common in both mechanical, civil, chemical, aerospace engineering and atmospheric science. Tensor notation is used in the teaching of the navier stokes equations which are very common. I actually work with inviscid fluids a lot which are described by the Laplace equations and I have done so many vector identity proofs with tensor notation it's scary.
I remember talking graduate math classes and the math majors bring stunned/troubled by me actually doing useful things with their math.