Question

Flow over a rocket outside the boundary layer is isentropic.

(a) False

(b) True

The question was asked during an online exam.

My enquiry is from A Brief Review of Thermodynamics in division Compressible Flow – Preliminary Aspects of Aerodynamics

Answer 1

Correct answer is (b) True

Explanation: The boundary layer regime over flow has dissipative effects and viscosity. This is not isentropic. But the flow outside has negligible viscosity, dissipative effects. Thus, it is a reversible process to a good approximation. Moreover, there is no heat exchange taking place to or from the fluid element, making this an adiabatic flow. So, outside the boundary layer, the flow is isentropic.