Hierarchical modeling for diffusion systems: Symmetrically-networked systems with rank one interconnection

In this paper, we propose a hierarchical modeling of the systems described by conservation laws. A conservation law on a hierarchically parted domain can be considered as a subsystem which interacts with neighbor elements through fluxes. Therefore, we regard the system as a networked system of each subsystem. The important idea is to weaken the interconnection in the sense of a rank. For detailed analysis of our method, we apply the proposed method to a diffusion equation. The hierarchical model is described by a non-circulant block Toeplitz matrix. Because the resulting system is symmetrically-networked system, we can show that the eigenvalues of the system consist of those of related uniform models. We also show that our method relaxes the stability condition of the fully discretized model. Finally we examine the performance of the hierarchical model by numerical simulations.