Simulation of Winter Air Pollution Dispersion Mechanism of Kathmandu Valley by Water-Tank Experiment

Article type: Research Article

Authors: Shrestha, M. L. | Kaga, A. | Kondo, A. | Inoue, Y. | Sugisawa, M. | Sapkota, B.

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: [email protected] | 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

Journal: Journal of Visualization, vol. 7, no. 4, pp. 317-329, 2004