Question

What will be the dimension of the flow consistency index for a fluid with a flow behaviour index of -1?

(a) N/m^2 s^2

(b) N/m^2 s

(c) N/ms

(d) N/ms^2

I got this question during an interview.

The query is from Types of Fluids topic in division Properties of Fluids of Fluid Mechanics

Answer 1

The correct answer is (b) N/m^2 s

For explanation: The relation between shear stress Z and velocity gradient  of a fluid is given by  where A is the flow consistency index and n is the flow behaviour index. If n = -1, A = Z * Unit of Z is N/m^2 and   is s^-1. Thus, the unit of A will be N/m^2 s.