WIAS Preprint No. 2473, (2018)

Optimal distributed control of two-dimensional nonlocal Cahn--Hilliard--Navier--Stokes systems with degenerate mobility and singular potential


  • Frigeri, Sergio
  • Grasselli, Maurizio
  • Sprekels, Jürgen
    ORCID: 0009-0000-0618-8604

2010 Mathematics Subject Classification

  • 35Q30 35R09 49J20 49J50 76T99


  • Navier-Stokes equations, nonlocal Cahn-Hilliard equations, degenerate mobility, incompressible binary fluids, phase separation, distributed optimal control, first-order necessary optimality conditions




In this paper, we consider a two-dimensional diffuse interface model for the phase separation of an incompressible and isothermal binary fluid mixture with matched densities. This model consists of the Navier-Stokes equations, nonlinearly coupled with a convective nonlocal Cahn-Hilliard equation. The system rules the evolution of the volume-averaged velocity of the mixture and the (relative) concentration difference of the two phases. The aim of this work is to study an optimal control problem for such a system, the control being a time-dependent external force acting on the fluid. We first prove the existence of an optimal control for a given tracking type cost functional. Then we study the differentiability properties of the control-to-state map, and we establish first-order necessary optimality conditions. These results generalize the ones obtained by the first and the third authors jointly with E. Rocca in [19]. There the authors assumed a constant mobility and a regular potential with polynomially controlled growth. Here, we analyze the physically more relevant case of a degenerate mobility and a singular (e.g., logarithmic) potential. This is made possible by the existence of a unique strong solution which was recently proved by the authors and C. G. Gal in [14].

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