An experimental study on aerodynamic critical phenomenon of notch-back car

The aerodynamic critical phenomenon of notch-back type automobile-like bodies was investigated experimentally. The aerodynamic forces were measured for the various bodies of different back-light rake angle at Re=O.8xlO5, I.Ox106 and 1.4xI06. Also, surface flow visuali­zation was effected by the oil mixture. It was found that the critical phenomenon for the notch-back type bodies was milder than for the hatch-back type bodies; the drag vs. slant angle curve for the hotch-back type bodies exihibiting local maximum was much smoother. Surface oil flow visualization revealed that the flow pattern associated with the critical pheno­menon was characterized by the reattachment of the separated flow on the boot. The effect of the forebody on the critical phenomenon was seen to be negligible

2014년 3차 미세입자 및 공기질 지식연구회

생활환경과 공기청정기술 미세먼지의 환경영향과 저감대책 □ 개요 ○ 행사명 : 2014년 3차 미세입자 및 공기질 지식연구회 개최 ○ 일시 : 2014. 09. 26(금) 16:00 ~ 19:00 ○ 장소 : 광주과학기술교류협력센터 중회의실A (062-609-0500) ○ 참석 대상 : 지식연구회 위원 28명 내

Ozone and NOx formation from the spark discharge aerosol generator using air as a carrier gas

An aerosol generator using spark discharge has applied to nanoparticle production. However, some by-products such as ozone, nitric oxide and nitrogen dioxide were simultaneously generated with particles in air. In this study, the generation characteristics of byproduct gases were investigated in terms of the air flow rates and the applied discharge power in spark discharge. The particle size distribution was measured using a SMPS system to observe the effect of gas absorption on silver nanoparticles. The results showed that NOx concentration increased linearly with discharge energy. However, ozone concentration increases with discharge energy in a low energy region, but decreases adversely with discharge energy in a high-energy region, which NOx concentration increases steeply in comparison of ozone concentration

Thermophoretic Effect on Particle Deposition Toward a Horizontal Wafer

To investigate thermophoretic effect on particle deposition, average deposition velocity toward a horizontal wafer surface in vertical airflow is measured keeping the wafer surface temperature different from the surrounding air temperature. In the present measurement, the temperature difference is maintained in the range from -10 to 4℃. Polystyrene latex (PSL) sphere of diameter between 0.3 and 0.8 μm are used for the experiment. The number of particles deposited on a wafer surface is estimated from the measurements using a wafer surface scanner (PMS SAS-3600). Experimental data are compared with prediction model results

Measurement of Particle Deposition Velocity toward a Horizontal Semiconductor Wafer Using a Wafer Surface Scanner

Average particle deposition velocity toward a horizontal semiconductor wafer in vertical airflow is measured by a wafer surface scanner(PMS SAS-3600). Use of wafer surface scanner requires very short exposure time normally ranging from 10 to 30 minutes, and hence makes repetition of experiment much easier. Polystyrene latex (PSL) spheres of diameter between 0.2 and 1.0 ㎛ are used. The present range of particle sizes is very important in controlling particle deposition on a wafer surface in industrial applications. For the present experiment, convection, diffusion, and sedimentation comprise important agents for deposition mechanisms. To investigate confidence interval of experimental data, mean and standard deviation of average deposition velocities are obtained from more than ten data set for each PSL sphere size. It is found that the distribution of mean of average deposition velocities from the measurement agrees well with the predictions of Liu and Ahn(1987) and Emi et al.(1989)

Ultra-fine particles and gaseous volatile organic compound exposures from the reaction of ozone and car-air freshener during metropolis travel

Ministry of Science and Technology project (Basic Science Research Program) and the Korea Institute of Science and Technology for the partial financial support of the research