ABSTRACT
A phenomenon observed in non-Newtonian fluids which is absent in Navier-Stokes fluids, is the presence of a normal stress component, additional to the pressure, determined by the velocity field. For second grade incompressible fluids which adhere to a boundary this component has been calculated explicitly by Berker [1], and the expression shows that for an incompressible Navier-Stokes flow, the component is zero.
