Question

In which one of the following cases can the equation of continuity be used?

(a) Compressible flow

(b) Incompressible flow

(c) Turbulent flow

(d) Viscous flow

This question was addressed to me in exam.

My enquiry is from Fluids Mechanical Properties topic in section Mechanical Properties of Fluids of Physics – Class 11

Answer 1

Right answer is (b) Incompressible flow

To explain: For using the continuity equation we assume that the flow is incompressible, laminar and non-viscous. The option that says compressible flow implies that fluid’s density can be changed. So it’s incorrect. The option that says turbulent flow is incorrect as we have to assume flow to be laminar for the equation of continuity to hold. The option that says viscous flow is also incorrect because we assume flow to be frictionless for the equation of continuity to hold.