Application of CFD methods for modelling in air pollution problems: Possibilities and gaps

Different urban air pollution problems deal with complex structure of air f lows and turbulence. For such problems the Computer Fluid Dynamics (CFD) me thods become widely used. However, this approach despite a number of advant ages has some problems. Experience of use of CFD tools for development of m odels and suggestions of their applications for a local scale air pollution over a complex terrain and stable stratification are discussed in this pap er, including: Topography and complex geometry: choose of the co-ordinate system and compu ter grid; Turbulence closure for air pollution modelling: modified k-epsilon model fo r stable stratified ABL; Boundary conditions for vertical profiles of velocity for stable-stratified atmosphere; Effects of the radiation and thermal budget of inclined surfaces to dispers ion of pollutants; Artificial sources of air dynamics and circulation. Some examples of CFD applications for air pollution modelling for a flat te rrain, mountainous area, mining open cast and indoor ventilation are discus sed. Modified k-epsilon model for stably-stratified ABL is suggested. Due t o the isotropic character of the k-epsilon model a combination of it in ver tical with the sub-grid turbulence closure in horizontal can be more suitab le for ABL. An effective scheme of boundary conditions for velocity profile s, based on the developed similarity theory for stable-stratified ABL, is s uggested. Alongside with the common studies of atmospheric dispersion, the CFD methods have also demonstrated a good potential for studying anthropoge nic and artificial-ventilation sources of air dynamic and circulation in lo cal-scale processes of air pollution.