Affiliations: Department of Environmental Engineering, Osaka
University, 2-1, Yamada-Oka, Suita, Osaka 565-0871, Japan. Tel: +81-6-6879-7670/Fax: +81-6-6879-7669;
E-mail: manohar@moon.env.eng.osaka-u.ac.jp | Institute of Engineering, Pulchowk Campus, Tribhuvan
University, Lalitpur, Nepal
Abstract: The air pollution concentration in Kathmandu valley in the winter
season was found to be higher than in the summer season due to the formation of
the inversion layer. This mechanism was simulated in the water-tank experiment
by measuring the temperature and flow field using liquid crystal thermometry
and particle image velocimetry. Thermal stratification was made at the
beginning of the experiment and the surface temperature of the valley model was
changed with 12 minutes period matching the diurnal field temperature pattern
of the Kathmandu valley. The updraft wind and Bernard convection occurred
during daytime and downdraft wind and inversion layer were realized during
nighttime. The temperature, flow field and mass dispersion characteristics
obtained in the water-tank experiment explained clearly the mechanism of air
pollution in Kathmandu valley.
Keywords: Kathmandu Valley, Water-Tank Experiment, Inversion Layer, Flow Field, PIV
