Question

The mathematical classification of inviscid flow equations are different from that of the viscous flow equations because of __________

(a) absence of viscosity coefficients

(b) absence of higher order terms

(c) absence of convective terms

(d) absence of diffusive terms

This question was posed to me in my homework.

This intriguing question originated from Classification of PDE in portion Mathematical Behaviour of Partial Differential Equations of Computational Fluid Dynamics

Answer 1

The correct option is (b) absence of higher order terms

The best explanation: The type of PDE is determined by the higher order terms. In the inviscid flow equations, the higher order terms are not present. So, the mathematical classification of inviscid and viscous flows is not the same.