Numerical Simulation Data and COMSOL Models for Reactive Fingering ($A+B \rightarrow C$) in Porous Media

Project Description This repository contains the numerical implementation and data for investigating hydrodynamic instabilities in a coupled Brinkman-flow and chemical reaction-diffusion system. The model specifically simulates viscous and density fingering occurring when two miscible fluids react to form a third product (A + B -> C) within a vertical porous domain. The implementation focuses on the non-linear coupling between flow and chemistry, in which the fluid density and viscosity depend on the local concentrations of chemical species. Technical Specifications Software: COMSOL Multiphysics® v6.3 Formulation: Full Velocity-Pressure-Concentration coupling (Non-pressure formulation) Interface: Weak Form PDE (Mathematics Module) Mesh: Approximately 125,500 triangular elements with refinement at the interface Solver: Time-dependent Implicit BDF (orders 1–5) Mathematical Model The system solves the following coupled PDEs: Incompressibility: $\nabla \cdot \mathbf{u} = 0$ Brinkman Momentum: $\frac{\partial \mathbf{u}}{\partial t} + \frac{\mu(c)}{K}\mathbf{u} = -\nabla p + \mu_{e} \Delta \mathbf{u} - \rho(a,c) \mathbf{g}$ Species Transport: $\frac{\partial \phi_i}{\partial t} + \mathbf{u} \cdot \nabla \phi_i = d_i \Delta \phi_i \pm \kappa ab$ (for $\phi_i = a, b, c$) Constitutive Relations Density: $\rho(a, c) = 1 + \alpha_A a + \alpha_C c$ Viscosity: $\mu(c) = \exp(Rc)$ File Structure weak_form_k_0_1_2.mph: The master COMSOL model file including physics settings and study configurations. Numerical_Data/: Exported data tables for concentration profiles and fingering metrics. Instructions for Use Open the .mph file in COMSOL Multiphysics® 6.3. Parameters: Adjust the log-mobility ratio ($R$), buoyancy coefficients ($\alpha_A, \alpha_C$), and reaction rate ($\kappa$) in the Global Definitions > Parameters section. Initial Condition: The interface is located at $y=100$. Random perturbations are generated using the rn1 function to trigger fingering. Execution: Right-click Study 1 and select Compute. Note: Due to high mesh density, a minimum of 16GB RAM is recommended. Citation If you use these models or data in your research, please cite: Kundu, S., Mishra, M. "Numerical Implementation of A+B -> C Reactive Flow in Porous Media," Zenodo (2026). 10.5281/zenodo.18887561 Contact Sahil Kundu (PhD Student) & Prof. Manoranjan Mishra (Advisor) Department of Mathematics, Indian Institute of Technology Ropar