This fundamental paper breaks down the different types of fluid dynamic flow configurations and gives the equations of the forces and moments of interaction between the most popular of these fluid dynamic singularities. IMHO the importance of having done that lies in the analytically derived stability of two singularities; the spherical vortex by Professor Hill and the gyration stabilized vortex of Professor Hicks and the earmarking of these singularities as the building blocks of matter formed by the flow of the ether by Carl Friedrick Kraft, Ott C. Hilgenberg, Gustav Le Bon, and others. Crucial to the understanding of this importance is the basic model of the ether as a fluidic medium to which compressible fluid dynamic equations can be applied, including coordinate transformations with the factor (1-v2/c2)1/2. This ether model has also primordial ambient scalar energy density, comparable to the atmospheric pressure of stagnant air. Note that energy density has the same dimensionality as hydrostatic pressure (Joules/cubic meter ~ in lb/cubic inch = lb/square inch). However; when flow singularities arise in the medium the local scalar pressure is reduced by the vectorial energy density of the directional flow field's velocity momentum. This is well expressed by the Bernouilli equation, where the potential (scalar) energy density (pressure) is reduced (minus sign) by the kinetic energy density of the local flowing medium, to give the lower static pressure as measured by an observer in the flow.
The meaning of the negative sign should not be underestimated. Its physical meaning is missing in Relativity. In fluid dynamics it explains the manifestation of forces. Fluid dynamics does not need the postulation of attraction forces at a distance due to gravitons, etc. Singularity flow by itself causes the local scalar pressure reductions and thus the pressure differentials, that create the pushing forces by the ambient scalar pressure, as they act, for example, on finite areas of stable singularities, that exhibit kinetic mass. To say that "forces exist first and therefore we have energy as a secondary" is wrong. Forces are due to field gradients, which are small pressure differentials, negatively superimposed on the high scalar pressure of a mediumand acting on areas.
