Question

Which of these differences occur in the momentum equation of the compressible flows when compared to that of the incompressible flows?

(a) Temperature term

(b) Source term

(c) Bulk viscosity

(d) Bulk modulus

This question was addressed to me in semester exam.

My question is based upon Compressible Flows topic in chapter Incompressible Flows & Compressible Flows of Computational Fluid Dynamics

Answer 1

The correct choice is (c) Bulk viscosity

For explanation I would say: In the incompressible flows, the bulk viscosity term is omitted as the density is constant. But, in the compressible flows, this cannot be omitted. This is an additional term in the momentum equation of the compressible flows.