Diffusive Smoothed Particle Hydrodynamics for Reactive Transport with Conservative Components in Heterogeneous Aquifers
Particle methods for the advection dispersion equation in heterogeneous aquifers present several advantages with respect to grid formulations, specifically on the issue of numerical dispersion. This is notorious in advection dominated conditions, with over diffusion of solute plumes influencing interpretation of reactive transport results. Smoothed Particle Hydrodynamics (SPH) is a method in which particles are interpreted as fluid volumes displaced by advection carrying multiple chemical species. The method solves solute concentration as a continuum which is convenient for computing chemical reactions on particles. Each specie is a transport equation, so for large chemical systems, introduction of Conservative Components reduces number of transport equations. These are combined linearly transforming reactive transport with equilibrium reactions into conservative transport of an equivalent component, following all quantities the same hydrodynamic dispersion. Applications of SPH to anisotropic dispersion in heterogeneous aquifers are limited and studies have reported negative concentrations in conservative simulations, which is of concern for reactive transport. Objective of this work is to address this result by reviewing three diffusive SPH models: Español & Revenga (ER), Anisotropic SPH for Anisotropic Diffusion (ASPHAD) and Two First Derivatives (TFD). For comparison purposes, these are applied to estimate reaction rates in calcite dissolution/precipitation at equilibrium with an initial injection of a dissolving solution. Reactive transport is modeled by Conservative Components in a synthetic 2D heterogeneous aquifer for high and low degree of heterogeneity, advection dominated transport and anisotropic dispersion. Results show that ASPHAD and TFD are free of negative values in conservative simulations whereas ER generates negative concentrations due to unphysical diffusion for mild dispersion anisotropy. Low heterogeneity aquifer preserves dissolving properties of injection whereas high spatial variability induces precipitation. This work presents two SPH schemes free of negative concentrations with potential for reactive transport modelling based on Conservative Components.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021