Dynamic nonlinear multicontinuum homogenization of systems with intrinsically evolving microstructure

In this paper, we propose a multicontinuum homogenization approach for nonlinear problems involving dynamically evolving multiscale media. The main idea of the proposed approach is that one of the fine-scale variables defines continua. It allows us to formulate macroscopic variables and derive new macroscopic models for nonlinear problems, where coefficients can depend on fine-scale functions. As an example, we consider a fingering problem and employ the fine-scale concentration field to define continua. We consider both Galerkin and mixed multicontinuum modeling approaches. In the former, the multicontinuum theory is applied to the pressure and concentration fields; in the latter, it is also applied to the velocity field. In both approaches, we provide multicontinuum expansions, formulate cell problems, and derive the corresponding macroscopic models. We present numerical results for model problems of gravity-driven fingering, viscous fingering, and interface flattening driven by high-contrast flow. The results show that the macroscopic models, derived with the proposed approach, can provide an accurate representation of the coarse-scale solutions. © 2026 The Author(s).