Question

What is the portion of the nozzle called where the angle between the tangent to the wall and horizontal decreases?

(a) Divergent section

(b) Expansion section

(c) Straightening section

(d) Convergen section

This question was posed to me during an online exam.

My question comes from Supersonic Nozzle Design in chapter Numerical Techniques for Nonlinear Supersonic Flow, Elements of Hypersonic Flow, Couette and Poiseuille Flow of Aerodynamics

Answer 1

Correct choice is (c) Straightening section

To explain: When we see the nozzle contour, there are two sections. One where the angle θ which is the angle formed between the tangent to the wall and horizontal increases until it reaches a maximum point. After this, θ reduces until it is equal to zero at the nozzle exit. This section is known as straightening section.