Quasi-variational principle and general quasi-variational principle for incompressible flow boundary value problems

In this paper, by multiplying pertinent virtual variables to the governing equations of incompressible viscous flow, and integrating the equations, and then adding them algebraically together, the quasi-variational principles for the incompressible viscous flow are established (such process is called variational integral method). At the last section of the paper, Hagen-Poiseuille's flow, a classical example, is presented to show the application of the quasi-variational principles of viscous flow boundary value problems.