Question

Which is true for a symmetry boundary?

(a) Diffusive flux is non-zero

(b) Diffusive flux is zero

(c) Convective flux is zero

(d) Convective flux is non-zero

The question was posed to me by my college director while I was bunking the class.

This is a very interesting question from Boundary Conditions topic in division Boundary Conditions of Computational Fluid Dynamics

Answer 1

Right choice is (c) Convective flux is zero

The explanation: The convective flux at a symmetry boundary is always zero. The diffusive flux may or may not be zero depending upon the coincidence of this boundary with the Cartesian coordinates.