Estimation of a motion equations system of a potential two-dimensional in a water flow plan to dimensionless form

In terms of stationary open water flow, the boundary conditions in the flow free spreading problem are reduced to a dimensionless form by the various coordinates and flow parameters' transformations, including I.A. Sherenkov's transformations, which bring the boundary value problem to a dimensionless form. It was found that the equations system itself can be reduced to a universal dimensionless form, but the boundary problem cannot be reduced, since the boundary conditions both at the flow outlet from a free-flow pipe and at the flow infinity downstream are not reduced to a universal dimensionless form. It is concluded that it is impossible to solve the boundary value problem once and then use this solution under any boundary conditions. It was also revealed that the problem solution depends on a dimensionless parameter-the Froude criterion at the flow outlet from the pipe. This proves that it is possible to build a universal graph, a universal method for solving the problem with Froude numbers at the flow outlet from the pipe more than unity or close to unity. But increasing the Froude number, it is necessary to build a series of graphs, and it is better to create a single theory, an algorithm for solving this problem.