Question

Which of these laws is used to find the heat flux at a point in the fluid?

(a) Fourier law

(b) Fick’s law

(c) Newton’s law

(d) Kepler’s law

This question was addressed to me by my school teacher while I was bunking the class.

This key question is from Couette Flow in chapter Numerical Techniques for Nonlinear Supersonic Flow, Elements of Hypersonic Flow, Couette and Poiseuille Flow of Aerodynamics

Answer 1

Correct choice is (a) Fourier law

Explanation: Fourier law which is also known as the law of heat conduction is used to find out the heat flux at any point in the fluid. It is given by the formula:

\(\dot {q}_y\) =  – k\(\frac {∂T}{∂y}\)

Where, heat flux is in the y – direction

Minus sign indicates that the heat flows from high temperature to low temperature and thus \(\dot {q}_y\) is in opposite direction to the temperature gradient.