论文信息 - A Study on the Effects of Porosity on Discharge Coefficient in Cross-Ventilated Buildings Based on Wind Tunnel Experiments

A Study on the Effects of Porosity on Discharge Coefficient in Cross-Ventilated Buildings Based on Wind Tunnel Experiments

Abstract A study was performed on the effects of porosity on discharge coefficient and airflow 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 porosities in the range 0.4% - 64%. The results of wind tunnel experiments suggest that the discharge coefficient increases when the porosity is higher. The results of CFD analysis reveal that the contraction of airflow when it passes through the opening is correlated with discharge coefficient, and that the discharge coefficient increases when flow contraction does not occur. When porosity increases, the retardment of the streamtube ceases to occur 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 the local dynamic similarity model on porosity, the effectiveness of the model was confirmed well when the porosity was 16% or lower regardless of wind direction. The validity of the model was also confirmed under the condition where airflow goes along the wall surface before reaching the opening even when the porosity was 36% or more.

[1] S. Murakami,et al. Wind Tunnel Test on Velocity-Pressure Field of Cross-Ventilation with Open Windows , 1991 .

[2] H.P.A.H. Irwin,et al. A simple omnidirectional sensor for wind-tunnel studies of pedestrian-level winds , 1981 .

[3] Andreas K. Athienitis,et al. Wind Driven Flow through Openings – A Review of Discharge Coefficients , 2004 .

[4] Yoshihiko Akamine,et al. Local Dynamic Similarity Model of Cross-Ventilation Part 1 - Theoretical Framework , 2004 .

[5] Yoshihiko Akamine,et al. Local Dynamic Similarity Model of Cross-Ventilation Part 2 - Application of Local Dynamic Similarity Model , 2004 .

[6] Mats Sandberg,et al. An Alternative View on the Theory of Cross-Ventilation , 2004 .

[7] Yoshihiko Akamine,et al. Local dynamic similarity concept as applied to evaluation of discharge co- efficients of cross-ventilated buildings. Part 2: Applicability of local dy- namic similarity concept , 2005 .

[8] B. J. Vickery,et al. External wind pressure distributions and induced internal ventilation flow in low-rise industrial and domestic structures , 1987 .

[9] T. Kurabuchi,et al. Local dynamic similarity concept as applied to evaluation of discharge coefficients of ventilated buildings. Part 1: Basic idea and underlying wind tunnel tests , 2006 .

[10] Shigeki Nishizawa,et al. Wind Pressure and Air Flow in a Full-Scale Building Model under Cross Ventilation , 2004 .