Analysis of a finite-difference and a Galerkin technique applied to the simulation of advection and diffusion of air pollutants from a line source
A finite-difference scheme and a Galerkin scheme are compared with respect to a very accurate solution describing time-dependent advection and diffusion of air pollutants from a line source in an atmosphere vertically stratified and limited by an inversion layer. The accurate solution was achieved by applying the finite-difference scheme on a very refined grid with a very small time step. The grid size and time step were defined according to stability and accuracy criteria discussed in the text. It is found that for the problem considered the two methods can be considered equally accurate. However, the Galerkin method gives a better approximation in the vicinity of the source. This was assumed to be partly due to the different way the source term is taken into account in the two methods. Improvement of the accuracy of the finite-difference scheme was achieved by approximating, at every step, the contribution of the source term by a Gaussian puff moving and diffusing with the velocity and diffusivity of the source location, instead of utilizing a stepwise function for the numerical approximation of the delta function representing the source term.
- Research Organization:
- Technital S.p.A., Via Carlo Cattaneo, 20, I-37121 Verona, Italy
- OSTI ID:
- 5684422
- Journal Information:
- J. Comput. Phys.; (United States), Journal Name: J. Comput. Phys.; (United States) Vol. 59:1; ISSN JCTPA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Comparison of Galerkin and control volume finite element for advection-diffusion problems.
Advection-dominated flows, with emphasis on the consequences of mass lumping. [Galerkin finite-element method]