Resolution of Pollutant Profiles in the Troposphere Using an Adaptive 3-D Unstructured Finite Volume Scheme

Wednesday, March 15, 2000 - 3:30pm - 4:25pm
Keller 3-180
Alison Tomlin (University of Leeds)
Joint work with Sakti Ghorai.

It has been shown that the accuracy of solution for atmospheric pollution dispersion problems is highly dependent on the computational mesh and in particular the degree of resolution. Course meshes have difficulties in resolving a large amount of the structure resulting from multi-scale source problems and complex meteorological fields. Finely resolved meshes on the other hand are computationally expensive and often prohibitive for reactive flow problems with a large number of chemical species. A solution to this problem is to provide extra resolution of the mesh where large solution errors or steep concentration gradients exist, leaving a course resolution elsewhere. In this way computational resources are utilized where they provide significant gains in accuracy. This paper presents a 3-D finite volume reactive flow model based on a transiently adaptive unstructured mesh. The use of tetrahedral mesh elements allows fully 3-D adaptivity and the flexibility to enable the code to handle complex structures arising from source terms of very different spatial scales. The paper will address issues such as mesh refinement criteria, the efficiency and accuracy of solutions resulting from different refinement methods, and the interpolation of emissions/meteorological data onto the unstructured mesh. Examples will be described for a number of different pollution dispersion problems covering a range of meteorological conditions. Results will demonstrate that the adaptive model is capable of achieving accuracy close to that of fixed high resolution meshes at a fraction of the computational cost.