A study was performed on the effects of porosity on discharge coefficient and air flow characteristics under the condition where uniform approaching flow directly faces to and enters the opening by using wind tunnel experiment and CFD analysis. The evaluation was performed on the porosity in the range of 0.4% - 64%. The results of wind tunnel experiment suggest that discharge coefficient increases when porosity is higher. The results of CFD analysis reveal that the contraction of air flow when it passes through the opening is correlated with discharge coefficient, and that discharge coefficient increases when flow contraction does not occur. When porosity increases, the retardment of streamtube does not occur any more in the region upstream of the opening, and this leads to the elimination of flow contraction, hence the increase of discharge coefficient. When we evaluated the limitation of application of local dynamic similarity model on porosity, the effectiveness of the model was confirmed well when porosity was 16% or lower regardless of wind direction, and that the validity of the model was also confirmed under the condition where air flow goes along wall surface before reaching the opening even when porosity was 36% or more.
Takashi Kurabuchi is a Professor of Department of Architecture, Faculty of Engineering, Tokyo University of Science, Tokyo, Japan.
He Graduated from University of Tokyo in 1982 and earned M.Eng. in 1984. He has been working at University of Tokyo since 1985 till 1992 as a research associate. He was concurrently assigned to National Institute of Science and Technology, formerly NBS, Maryland, U.S. as a guest scientist in 1986. He earned Dr. Eng. in 1991 from University of Tokyo. He has been working at Tokyo University of Science since 1992.
He has been studying numerical simulation of air flow in and around building, contaminant dispersion and ventilation efficiency, and measurement of velocity distribution, ventilation flow rate and performance of ventilation equipments. During his stay in NIST, he opened his self-developed 3D turbulent flow code as a public domain. Currently, he is leading several research projects relating to ventilation and academic standards in SHASE.
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