Question

Which of the equations governs the linearized incompressible flow over an airfoil at subsonic velocity using transformed coordinate system?

(a) Laplace’s equation

(b) Euler’s equation

(c) Navier – Stokes equation

(d) Cauchy’s equation

The question was asked in examination.

This key question is from Linearized Subsonic Flow in division Linearized and Conical Flows of Aerodynamics

Answer 1

The correct answer is (a) Laplace’s equation

The explanation: The compressible linearized perturbation velocity potential equation is transformed into incompressible using a transformed coordinate system (ξ, η). The equation is given by

ϕξξ + ϕηη = 0

This is the Laplace equation representing the incompressible flow in a linearized form.