ABSTRACT
John von Neumann was well aware of the tremendous difference between what happens when you don’t have the viscous terms [in the equations of motion] and when you do, and he was also aware that, during most of the development of hydrodynamics until about 1900, almost the main interest was in solving beautiful mathematical problems with this approximation which had almost nothing to do with real fluids. He characterised the theorist who made such analyses as a man who studied “dry water”.
