Pointwise Tracking Optimal Control Problem for Cahn Hilliard Navier Stokes system

TL;DR

This paper investigates a pointwise tracking optimal control problem for the 2D Cahn-Hilliard Navier-Stokes system, addressing low regularity challenges and deriving optimality conditions with applications to limited sensor data scenarios.

Contribution

It establishes existence, differentiability, and optimality conditions for a novel pointwise tracking control problem in fluid dynamics with limited sensor data.

Findings

Existence of strong solutions and optimal controls.

Derivation of first-order necessary optimality conditions.

Extension to singular potentials.

Abstract

We study a pointwise tracking optimal control problem for the two-dimensional local Cahn Hilliard Navier Stokes system, which models the evolution of two immiscible, incompressible fluids. The source term in the Cahn Hilliard equation acts as a control, and the cost functional measures the deviation of the phase variable from desired values at a finite set of spatial points over time. This setting reflects realistic applications where only a limited number of sensors are available. We also study a variant of the above pointwise tracking control problem where the cost is incorporated with a terminal time pointwise tracking term. The main mathematical difficulty arises from the low regularity of the cost functional due to the pointwise evaluation of the state variables. We prove the existence of strong solutions, establish the existence of an optimal control, and the differentiability of the control to state mapping. We define the adjoint system using a transposition method to characterise optimal control. Moreover, a first-order necessary optimality condition is derived in terms of the adjoint for both problems. Furthermore, we prove that our analysis can be extended to the case of singular potentials.