Complex fluid mechanics problems would be impossible to solve without the use of computational fluid dynamics (CFD). CFD is a powerful tool and allows a better understanding of the flow pattern and gives an entire view of the complex physics underlying different phenomena. In this dissertation, I utilized CFD technique to study complex flows including 1) The influence of roadside solid and vegetation barriers on near-road air quality, 2) Impacts of built structures on neighborhood PM2.5 pollution level, 3) Hot gas ingestion into the rotor-stator disk cavities of a subscale 1.5-stage axial gas turbine, 4) Hydrodynamics characterization of stem cell cultures.
Reynolds Averaged Navier-Stokes (RANS) technique coupled with the k-ε realizable turbulence model is utilized to investigate the flow pattern and pollutant concentration. A scalar transport equation is solved for a tracer gas to represent the roadway pollutant emissions. To validate numerical methodology, predicted pollutant concentration is compared with the wind tunnel data. Results show that the solid barrier induces an updraft motion and lofts the vehicle emission plume. Dense canopies act in a similar manner as a solid barrier and mitigate the pollutant concentration through vertical mixing. On the other hand, the high porosity vegetation barriers reduce the wind speed and lead to a higher pollutant concentration.
The modeling work proceeded to investigate influence of different building morphology on the neighborhood particulate level. It was found that Significant changes in pollutant concentration were caused by chimney height and building configuration, while the averaged concentration is less sensitive to packing density.
Next, both radial and circumferential pressure distributions are analyzed to get deeper insight into rotationally and externally induced hot gas ingestion in axial gas turbines. The circumferential pressure peak-to-trough amplitude is significantly attenuated in the cavity region compared to annulus region. Finally, different purge flow rates and rotational speeds are examined.
Finally, I employ Large Eddy Simulation (LES) technique to study the hydrodynamic characteristics of fluid flow in a CorningTM spinner flask and a rotary wall bioreactor. The results show that the cell aggregate size does not exceed the Kolmogorov length scale.