### Being irrotational and viscous

#### by Yi Zhang

I have been working on something involving both potential flows and turbulent flows, and this is how I found fascinating work by Daniel D. Joseph. In one of his papers, Potential flow of viscous fluids: Historical notes, one can get a peek of the missing link in our textbooks. I have also learned a lot in his web page about the same topic. His other two books I can put my hands on, Stability of Fluid Motions, Elementary Stability and Bifurcation Theory, are the standard textbooks for those topics as well. Shame on me, even though I read those two books, I am not aware of this potential viscous flow, making me wonder how fast I am drifting away from theoretical fluid dynamics with only the computing stuff in my mind.