Maximum Dissipation Principle for Designing Numerical Method in Complex Fluids

I will talk about the general energetic variational approaches for hydrodynamic systems of complex fluids. In these energetic variational approaches, the least action principle (LAP) with action functional gives the Hamiltonian parts (conservative force) of the hydrodynamic systems, and the maximum/minimum dissipation principle (MDP), i.e., Onsager’s principle, gives the dissipative parts (dissipative force) of the systems. When we combine the two systems derived from the two different principles through the force balance law, we obtain a whole coupled nonlinear system of equations satisfying the dissipative energy laws. Also, I will discuss the important roles of MDP in designing numerical method for computations of hydrodynamic system in complex fluids. The MDP is employed in the reformulated dissipation to obtain the dissipative force for the hydrodynamic system. The systems are consistent with the Hamiltonian parts which are derived from LAP. This procedure allows the usage of lower order element (a continuous C finite element) in numerical method to solve the system rather than high order elements, and at the same time preserves the dissipative energy law. Finally, I will show some numerical results of the free interface motion in the mixture of two different fluids.