A note on irrotational viscous flow

This Brief Communication describes features of steady irrotational flow in a viscous fluid. The aim is to illustrate, in a simple manner, the different roles played by viscous forces (which are identically zero) and viscous stresses (which are not), the differences in behavior of stagnation pressure (which is constant along a streamline even in the presence of viscous dissipation) and stagnation enthalpy (which changes through the flow), and the role of viscous stresses on the boundary in creating these behaviors.