A multi-mesh adaptive scheme for air quality modeling with the finite element method

Abstract

A multi-mesh adaptive scheme for convection-diffusion-reaction problems is presented. The proposal is applied to air quality modeling, especifically to the simulation of a pollutant punctual emissions. The performance of the proposal is analyzed with different nonlinear reaction models, including the photochemical model CB05 implmented within the Comunity Multiscale Air Quality model, which involves sixty-two species and very different characteristic reaction times. The problem is solved with splitting of transport and reaction processes. This allows to discretize the species in distinct computational meshes, adapted to the distribution of the error indicator of each case. A common reference mesh is used for all species and during all problem evolution. A remeshing technique based on imposing the volume of new elements is used to define and update the computational meshes. An error indicator well suited for problems involving large variation of the unknowns is used. A single-mesh strategy, with remeshing adapted to the most demanding specie in each part of the domain, is used for comparison. The results of the examples presented show that the accuracy of single and multi-mesh strategies are similar. Instead, computational cost of multi-mesh is lower than single-mesh in most cases. Reduction increases with the number of species and the number of plumes. An example of a punctual emissor in a three-dimensional domain, with realistic values of CB05 components, is presented.