Navier and Stokes Equations
For a viscous flow, the relationships between the normal/shear stresses and the rate of deformation (velocity field variation) can be determined by making a simple assumption. That is, the stresses are linearly related to the rate of deformation (Newtonian fluid). (see chapter 5-4.3) The proportional constant for the relation is the dynamic viscosity of the fluid (m). Based on this, Navier and Stokes derived the famous Navier-Stokes equations: