Question

Characteristic lines are those lines in the flow field where the flow variables cannot be determined.

(a) True

(b) False

The question was asked in an interview.

Question is from Supersonic Nozzle Design in portion Numerical Techniques for Nonlinear Supersonic Flow, Elements of Hypersonic Flow, Couette and Poiseuille Flow of Aerodynamics

Answer 1

Correct option is (a) True

Best explanation: There exists some lines in a flow field where the derivatives of the flow variables are indeterminate. For example, along the flow if we assume that there’s a point P, there will be a line along this point where \(\frac {∂^2 ϕ}{∂x∂y}\) is indeterminate as it takes 0/0 form. This line is known as the characteristic line.