Computational fluid dynamics research

Computational fluid dynamics (CFD) research in the Atmospheric Dispersion Modelling group is focusing 1) in particular on the surface layer of the urban atmospheric boundary layers, and 2) more generally on the atmospheric boundary layer dynamics in local scale.

Our CFD-based research utilizes very high-resolution large-eddy simulation (LES) which is employed and further developed for these research areas. The LES model called PALM developed at Leibniz Universität Hannover is run on the Cray XC-40 supercomputer of FMI.

The first research area has several motivations. Detailed, building resolving LES modelling of urban canopy-layer flow and dispersion opens possibilities e.g. to more detailed and more reliable air-quality analyses, contingency planning and post analyses of hazardous material release accidents. Moreover, it can be applied to city-planning purposes to achieve better air-quality, pedestrian wind comfort and thus improved life quality as well as better energy efficiency in new urban areas being currently built or planned especially in Helsinki-region because of its increasing population.

LES-modelled dispersion of traffic emissions on and around a planned city boulevard (report of the study)


LES-modelled instantaneous wind field shown on a vertical cutplane in central Helsinki


The second research area includes especially studies of the dynamics of convective boundary layers in collaboration with Prof. Sergej Zilitinkevich. Various hypotheses are practically impossible to be tested based on measurements. Such hypotheses are tested using the LES modelling. This research aims at improved parameterizations and their calibration for numerical weather-prediction models and climate models, and better understanding of the underlying dynamics.