Viscosity solutions of Hamilton-Jacobi-Bellman equations for optimal control problem of local Cahn-Hilliard-Navier-Stokes system

In this work, we consider the local Cahn-Hilliard-Navier-Stokes equation with regular potential in a two-dimensional bounded domain. We formulate a distributed optimal control problem as the minimization of a suitable cost functional subject to the controlled local Cahn-Hilliard-Navier-Stokes system and define the associated value function. We prove the Dynamic Programming Principle satisfied by the value function. Due to the lack of smoothness properties for the value function, we use the method of viscosity solutions to obtain the corresponding solution of the infinite-dimensional Hamilton-Jacobi-Bellman equation. We show that the value function is the unique viscosity solution of the Hamilton-Jacobi-Bellman equation. The uniqueness of the viscosity solution is established via the comparison principle.