Water-art problems at Sanssouci—Euler’s involvement in practical hydrodynamics on the eve of ideal flow theory

Frederick the Great blamed Euler for the failure of fountains at his summer palace Sanssouci. However, what is regarded as an example for the proverbial gap between theory and practice, is based on dubious evidence. In this paper I review Euler’s involvement with pipeflow problems for the Sanssouci water-art project. Contrary to the widespread slander, Euler’s ability to cope with practical challenges was remarkable. The Sanssouci fountains did not fail because Euler was unable to apply hydrodynamical theory to practice, but because the King ignored his advice and employed incompetent practitioners. The hydrodynamics of the Sanssouci problem also deserves some interest because it happened on the eve of the formulation of the general equations of motion for ideal fluids. Although it seems paradoxical, the birth of ideal flow theory was deeply rooted in Euler’s involvement with real flow problems.