Using CFD and mathematical optimization to investigate air pollution due to stacks

This paper describes the use of Computational Fluid Dynamics (CFD) and math ematical optimization techniques to minimize pollution due to industrial so urces like stacks. The optimum placement of a new pollutant source (e.g. a new power plant with its stacks) depends on many parameters. These include stack height, stack distance from surrounding populated areas, barriers, lo cal meteorological conditions, etc. As an experimental approach is both tim e-consuming and costly, use is made of numerical techniques. Using CFD with out optimization on a trial-and-error basis, however, does not guarantee op timal solutions. A better approach, that until recently has been too expens ive, is to combine CFD with mathematical optimization techniques, thereby i ncorporating the influence of the variables automatically. The current stud y investigates a simplified two-dimensional case of the-minimisation of pol lutant stack distance to a street canyon with or without barrier for a give n maximum ground-level concentration of pollutants in a street canyon. Two to five design variables are considered. The CFD simulation uses the STAR-C D code with RNG k-epsilon turbulence model. Making use of initial field res tarts drastically reduces CFD solution time. The optimization is carried ou t by means of Snyman's DYNAMIC-Q method, which is specifically designed to handle constrained problems where the objective or constraint functions are expensive to evaluate. The paper illustrates how the parameters considered influence the stack placement and how these techniques can-be used by the environmental engineer to perform impact studies of new pollutant sources. Copyright (C) 1999 John Wiley & Sons, Ltd.