Fundamental Nature of Viscous Incompressible Flow and Minimization of Fluid Dynamic Drag

Abstract

The fundamental nature of viscous incompressible flow is investigated by integrating the first and second laws of thermodynamics. The free energy of fluid, the fundamental thermodynamic function for system equilibrium, is shown to be a synthetic combination of the entropy production rate, flow steadiness and Lagrange function (kinetic energy – potential energy). When the flow is stationary and there is no energy exchange at the boundary, the principle of minimum entropy production rate in the thermodynamics of irreversible processes is extended to the space integration of the flow field. The results for minimizing the dynamic drag of fluid flow are discussed.