The Effect Of Window Opening Percentage And Solar Radiation On The Flow Field In Street Canyon

For most civil buildings, wind-driven natural ventilation is the main approach of natural ventilation, and also an important way of improving indoor air quality and thermal environment. It is obvious that stable air flow rate is necessary to maintain a healthy and comfortable indoor air quality and thermal environment in the natural ventilation room.When using the equation of natural ventilation, the building is usually regarded as a block. However, in fact people will open windows for better indoor environment (especially in spring and autumn), and if the most windows of the side wall of a building are open, then the air flow of the street canyon may be influenced, thus affect the applying of the natural ventilation equation. In addition, when a side wall of a building receive solar radiation and is heated, the upward buoyancy near the side wall will affect the air flow in the street canyon, thus thermal effect is also an important factor.The present study investigated the window opening percentage (WOP) and the temperature difference between back ground air and the heated side wall in Shanghai, based on the data, the study discuss the flow field and temperature field by numerical simulation with different WOPs and thermal conditions.The results show that the effect of WOP on the static pressure difference (SPD) of the upwind building is negligible, while that of the downwind building can not be ignored. Therefore it is necessary to consider the WOP effect when calculating the air flow rate of the natural ventilation rooms in the downwind building. In order to obtain an applicable correction for air flow rate calculation of wind-driven natural ventilation, a correction factor, i.e. k, is introduced and the ranges of κ for different WOPs are also determined from the analysis, and0.43<k<0.49when the WOP is4.44%; while0.32<k<0.36when the WOP is9.78%. Since the thermal conditions may affect the static pressure distribution around buildings, an influence factor w is defined to discuss this effect. The values of w decrease with the increase of wind speed for both upwind and downwind buildings, and it appears that the influence of thermal conditions on the pressure distributions of downwind buildings is greater than that of upwind buildings. When VH reaches a critical value, i.e. Vc, the values of w are below5%, and the influence of thermal effects on the pressure distributions can be ignored. The values of Vc depends on the thermal conditions.