Testing and analysis of rainwater quality in Shenyang

To explore the influence of rainwater quality on rain utilization projects the rainwater of building roofs community runoff and municipal outlets which were taken from Hunnan New District of Shenyang was detected and analyzed for one year. The results show that the main pollutants affecting the quality of the rainwater are chemical oxygen demand COD and suspended solids SS which is especially obvious at the beginning of rainfall. With the duration of the rainfall water quality improves.The contents of COD and SS in municipal outlets are the highest which are 167 to 249 mg/L and 119 to 332 mg/L respectively. The contents of COD and SS are 27 to 85 and 106 to 269 mg/L in community runoff 15 to 80 and 50 to 153 mg/L in the rainwater of building roofs.NH4＋-N concentrations of the three sampling sites are 1.7 to 5.2 3.7 to 18.2 and 5.2 to 25.6 mg/L.

NUMERICAL STUDIES ON AIRFLOW AND POLLUTANT DISPERSION IN URBAN STREET CANYONS FORMED BY SLANTED ROOF BUILDINGS

Based on the CFD technique, fifteen cases were evaluated for the airflows and pollutant dispersions inside urban street canyons formed by slanted roof buildings. The simulated wind fields and concentration contours show that W/H, W/h and h/H （where W is the street width, and Hand h are the heights of buildings at the leeward and windward sides of the street, respectively） are the crucial factors in determining the vortex structure and pollutant distribution within a canyon. It is concluded that （1） in a symmetrical canyon, at W/H =0.5 two vortices （an upper clockwise vortex between the slanted roofs and a lower counter-clockwise one） are developed and pollutants accumulate on the windward side of the street, whereas at w/H=2.0 only one clockwise vortex is generated and thus pollution piles up on the leeward side, （2） in a step-up canyon with W/H=0.5 to 2.0 （at h/H =1.5 to 2.0）and a step-down canyon with W/h=1.0 （at h/H =0.5 to 0.667）, the pollution level close to the lower building is higher than that close to the taller building since a clockwise vortex is generated in the step-up canyon and a counter-clockwise one in the step-down canyon, （3） in a narrow step-down canyon with W/h=0.5 （at h/H =0.667） very poor ventilation properties is detected, and inside a wider step-down canyon with W/h=2.0 the vortex structure and consequently pollutant distribution varies greatly with h/H.

Study of the wind-pressure distribution of flat-roof parabolic condensers based on wind-tunnel tests

The structure of parabolic condensers makes them susceptible to wind load because of their thin and large windward mirrors.In this paper,the wind pressure on a model of a condenser mirror(1:35)on multistorey flat roofs is analysed via pressure measurement in a wind tunnel.The mean wind-pressure distribution law of flat-roof condenser mirrors(including the change law with working conditions and the maximum distribution characteristics)and the distribution law of fluctuating and extreme wind pressure are obtained.Furthermore,by comparison with the ground-based condenser distribution law,similarities and differences between the two are obtained.Research results show that the wind-pressure distribution law of flat-roof parabolic condenser mirrors is the same as those on the ground,but the mean wind-pressure coefficient(absolute value)is generally~30%smaller.Furthermore,the maximum effect is generally located at the windward mirror edge and the mirror is more susceptible to wind pressure in wind directions of 30°and 135°-150°.The results of this study can provide a theoretical reference for wind-resistant structure design and multistorey flat-roof condenser-related research.