Biomedical subjects

Chung-Yi Chung

Publications and source records attributed to Chung-Yi Chung.

3 recordsLinked to original sources

PubMed2006

A numerical and experimental study of pollutant dispersion in a traffic tunnel.

Three-dimensional turbulent flow and dispersion of gaseous pollutants carbon monoxide (CO) and nitrogen oxides (NOx) in a road tunnel was modeled using the standard k-epsilon turbulence model and solved numerically using the finite volume method. Vehicle emissions were estimated from the measured traffic flow rates and modeled as banded line sources along the tunnel floor. The effects of fan ventilation and piston effect of moving vehicles on the airflow and pollutant dilution were examined. The numerical results reveal that a peak velocity exists near the tunnel floor due to the piston effect of vehicles. The cross-sectional concentrations of air pollutants are non-uniformly distributed and concentrations rise with downstream distance. The piston effect of vehicles can alone provide 25%-34% dilution of air pollutants in the tunnel, compounded 43%-70% dilution effect according to the ventilation condition.

Air Pollutants↗

PubMed2006

Estimating air quality in a traffic tunnel using a forecasting combination model.

This study compared three forecasting methods based on their accuracy or absolute errors in forecasting air pollution in a traffic tunnel: the Grey model (GM), the Crank-Nicholson implicit scheme model, and the forecasting combination model (FCM). Three criteria, root mean square error (RMSE), the mean absolute error (MAE) and mean absolute percentage error (MAPE), were applied to the models and the FCM model displayed all of the characteristics of a good forecasting model. The correlation coefficient (r) for the FCM model equaled 0.94 (Upwind), 0.98 (Middle) and 0.98 (Downwind). This study indicated that FCM can be used to accurately forecast CO pollution in the Kaohsiung Cross Harbor Tunnel.

Air Pollutants↗

PubMed2002

Measurement and three-dimensional modeling of airflow and pollutant dispersion in an undersea traffic tunnel.

Airflow and pollutant dispersion in a cross-harbor traffic tunnel were experimentally and numerically studied. Concentrations of the gaseous pollutants CO, NOx, and total hydrocarbons (THC) at three axial locations in the tunnel, together with traffic flow rate, traffic speed, and types of vehicle were measured. Three-dimensional (3D) turbulent flow and dispersion of air pollutants in the tunnel were modeled and solved numerically using the finite volume method. Traffic emissions were modeled accordingly as banded line sources along the tunnel floor. The results reveal that cross-sectional concentrations are nonuniformly distributed and that concentrations rise with downstream distance. The piston effect of vehicles alone can provide 9-23% dilution of air pollutants in the tunnel, compounded to a 23-74% dilution effect according to the ventilation condition.

Air Movements↗