The Numerical Simulation of Uplifted Street Canyon On Flow Field Structure And Pollutant Diffusion

The flow field structure, pollutant concentration distribution and dimensionless concentration evolution of uplifted street canyon has been analyzed in this study. Different from the ideal street canyon, the pollutant concentration distribution of the uplifting street canyon is higher at the bottom, lower at the top, higher at the windward side and lower at the leeward side. The total pollutant concentration (TPC) generally decreases with the increase of leeward building lifting height while the lift height increases with the same total building height or the total building height increases with increase in the lifting height. It is beneficial to the pollutant emission of in street canyon. On the contrary, the TPC increases when the total building height increases with the same lift height. The main reason is that the vertical length of the vortex increases, which is more difficult for pollutants to be discharged from the street canyon.

Advanced mobile-DOAS techniuqes for locating and identifying urban area emission sources

<p>Pollutant concentration distribution and emission are important ways to understand regional pollution. To investigate the distribution characteristics and identify individual sources rapidly, a new mobile passive differential optical absorption spectroscopy (DOAS) instrument has been developed, which set two angle telescopes (90°,30°) to receive the scattered light respectively, and set two mechanical shutters to switch the optical path quickly in the mobile platform. The instrument collected the zenith scattered light in the UV or visible region and it was used to derive the vertical column density of trace gases above the measurement route. The slant column density in two different viewing directions were detected, and combined with the geometric approximation, the vertical column density of trace gas was obtained. After obtaining the column concentration distribution, the data were analyzed by semi variance analysis combined with geographical information. Monte Carlo simulation was used to reconstruct the high spatial resolution pollutant concentration distribution, combined the wind field data during the observation, the high spatial resolution emission flux in the area can be quickly obtained. A field experiment was performed in Beijing and some industrial area. The distribution information of vertical column density along the route in Beijing was derived, the concentration distribution of NO<sub>2</sub> at 200m *200m resolution and the 0.01° *0.01°resolution emission flux data are obtained further. The new mobile multi light DOAS instrument were operated on a car. The NO<sub>2</sub> column density spatial distribution and the emission flux spatial distribution are obtained with the maximum value of 8.57×1016 molec./cm<sup>2</sup> and 34.8 ug/m<sup>2</sup>/s over the Beijing fifth ring road area. The scheme can provide a new method to verify pollutant concentration distribution and emission inventory.</p>

Numerical Simulation for Migration of the Pollutants in Soil

In the soil environment，through analyzing the numerical solutions of pollutant migration, the time-space law of the transmission of organic pollutants in soil can be mastered, which has both theoretical and practical significance. The general mathematical model of the migration of volatile pollutant in soil was established; and typical models of pollution sources emission were calculated, and the influence of various parameters in model on calculation results were compared, such as diffusion, convection, adsorption and degradation parameters; finally a correlation analysis and discussion was made on calculation results of the pollutant concentration distribution. The calculation results show that the convection is the main reason causing pollutants migration, and the influence of volatility to migration process cannot be ignored. It provides the scientific basis and approach for the pollution forecasting and prevention.

Numerical Analysis of Microclimate of Desk Displacement Ventilation Using a Zero-equation Turbulence Model

A computational fluid dynamics (CFD) program based on a zero-equation turbulence model is used to simulate the microclimate in a model office ventilated by desk displacement ventilation (DDV). DDV is a new ventilation concept that intends to combine the positive features of displacement ventilation and local task ventilation. The CFD model correctly predicts both the thermal plume and temperature stratification, and the calculated air temperature distributions agree with the measured data. The pollutant concentration distribution is further simulated to evaluate the microclimate of DDV. Results show that despite rather large discrepancies between simulated velocity distributions and experimental data, the zero-equation turbulence model may simulate the main characteristics (thermal plume, temperature, and qualitative velocity tendency) of DDV more quickly than other commonly used models, for instance, the k-ε model, and thus may be applied to similar cases in indoor environment design.