Adaptation of Pressure Based CFD Solvers for Mesoscale Atmospheric Problems

• Published in: Boundary - layer meteorology 2009-04, Vol.131 (1), p.85-103
• Main Authors: Kristóf, Gergely, Rácz, Norbert, Balogh, Miklós
• Format: Article
• Language: English
• Subjects: Air quality; Analysis methods; Applied sciences; Atmospheric boundary layer; Atmospheric pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Atmospherics; Computational Fluid Dynamics; Computer simulation; Convection; Coriolis force; Dispersion of pollutants; Earth and Environmental Science; Earth Sciences; Energy balance; Exact sciences and technology; Fluid dynamics; Hydrodynamics; Mathematical analysis; Mathematical models; Mesoscale flows; Meteorology; Nesting; Original Paper; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Pollution dispersion; Solvers; Surface energy; Thermal stratification; Transformation; Urban areas; Urban heat island; Urban heat islands; Vertical flow
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-008-9325-7

General purpose Computational Fluid Dynamics (CFD) solvers are frequently used in small-scale urban pollution dispersion simulations without a large extent of ver- tical flow. Vertical flow, however, plays an important role in the formation of local breezes, such as urban heat island induced breezes that have great significance in the ventilation of large cities. The effects of atmospheric stratification, anelasticity and Coriolis force must be taken into account in such simulations. We introduce a general method for adapting pressure based CFD solvers to atmospheric flow simulations in order to take advantage of their high flexibility in geometrical modelling and meshing. Compressibility and thermal stratification effects are taken into account by utilizing a novel system of transformations of the field variables and by adding consequential source terms to the model equations of incompressible flow. Phenomena involving mesoscale to microscale coupled effects can be analyzed without model nesting, applying only local grid refinement of an arbitrary level. Elements of the method are validated against an analytical solution, results of a reference calculation, and a laboratory scale urban heat island circulation experiment. The new approach can be applied with benefits to several areas of application. Inclusion of the moisture transport phenomena and the surface energy balance are important further steps towards the practical application of the method.