Fully-Discrete Provably Lyapunov Consistent Discretizations for Convection-Diffusion-Reaction PDE Systems

Abstract Convection-diffusion-reaction equations are a class of second-order partial differential equations (PDEs) widely used to model phenomena involving the change of concentration/population of one or more substances/species distributed in space. Understanding and preserving their stability properties in numerical simulations is crucial for accurate predictions, system analysis, and decision-making. This work focuses on the development of a comprehensive numerical framework for a class of convection-diffusion-reaction systems with a dissipative Lyapunov (or entropy or free energy) functional, $${\tilde{V}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>V</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:math> . This non-increasing Lyapunov functional is the driving quantity of the stability and properties of the system. We introduce a systematic methodology for constructing discretizations that mimic the stability analysis of the continuous model using Lyapunov’s direct method-type approach. The spatial algorithms are based on collocated discontinuous Galerkin (DG) methods with the summation-by-parts (SBP) property and the simultaneous approximation term (SAT) approach for imposing interface coupling and boundary conditions. Relaxation Runge-Kutta schemes are used to integrate in time and achieve fully discrete Lyapunov consistency. To verify the properties of the new schemes, we numerically solve a system of convection-diffusion-reaction PDEs governing the dynamic evolution of monomer and dimer concentrations during the dimerization process. Numerical results demonstrated the accuracy and consistency of the proposed discretizations. The new framework can enable further advancements in the analysis, control, and understanding of general convection-diffusion-reaction systems.