VARIATIONAL THEORIES IN HYDRODYNAMICS AND HYDRAULICS

Hydrodynamic and hydraulic theories have been developed along two para llel approaches, i.e., the vectorial and variational approaches. Most classical hydraulic theories are based on vectorial approaches. The va riational approach is a scalar approach based on the maximization of e ntropy, minimization of energy, or minimization of energy dissipation rate. A review of variational theories and hypotheses shows that funda mental theories in hydrodynamics and hydraulics derived from vectorial approaches can also be independently derived from variational approac hes. A comparison of different variational theories indicates that the y are consistent with each other provided that the concepts of entropy and energy are properly defined and correctly applied.