the meaning of "mag"?
 

Hello there,

I met some problems about unit. What is the result of the following formula?

(2.0)*mag(symm(fvc::grad(U)))

Is it the square of strain rate (unit:s^-2) ?

What is the meaning of "mag"?

mag = magnitude

Thank you for your reply.
Dose this means "mag(symm(fvc::grad(U)))" has no unit?
But the error information shows the unit of "(2.0)*mag(symm(fvc::grad(U)))*nu()" is "[0 2 -2 0 0 0 0]". Why is it the unit of nu [0 2 -1 0 0 0 0]?

nu is the kinematic viscosity with unit m^2/s.
U is velocity with unit m/s
grad is derivative with unit 1/m
Multiply all of them and you get m^2/s * m/s * 1/m = m^2/s^2
Everything is fine.