ERCIM News No.22 - July 1995 - CWI

Numerical Algorithms for Transport-Chemistry Problems

by Jan Verwer

At CWI new numerical techniques are developed and used in the study of the transport of pollutants. More in particular the studies concentrate on three applications: transport simulation of pollutants and sediments in shallow seas, transport simulation of trace constituents in the global troposphere, and smog prediction.

Negative effects of emission of pollutants in the atmosphere, groundwater and surface water become more and more noticeable in our environment: smog in urban regions, ground water contamination, the growth of algae in surface water, and even atmospheric climate change has to be feared. In the study of the long term effects of these emissions and in the prediction of the efficiency of policy decisions to reduce the effects mathematical simulations become increasingly important. The processes are described by a large system of coupled time dependent three-dimensional partial differential equations of the advection-diffusion-reaction type, one for each chemical species that plays a role in the reactive chain. Computer capacity is a critical factor here, and although computer power continues to expand, the computational requirements for high resolution transport models with full chemistry are still out of range for many applications.

Numerical analysis can help to find more efficient simulation tools and to fully exploit emerging computer architectures such as advanced multi-vector processors and massively parallel processing systems. In realistic environmental models the number of species can be large, for example up to 100 in current atmospheric models. Also the spatial domain can be large, requiring hundred thousands to millions of grid points. Moreover, in order to study long term effects, the equations have to be integrated over long time intervals. Such models require an excessive amount of CPU and memory which necessitates fast and efficient algorithms, even on modern supercomputers. This poses a number of outstanding numerical challenges.

Computational grid at ground level at the end of a 5-day prediction of SO2 concentrations

CWI has contributed in several ways to the solution of these problems.

The research at CWI is carried out in three projects:

Please contact:
Jan Verwer - CWI
Tel: +31 20 592 4095

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