Study on the influence of voids on high-rise building on the wind environment

Li, Yangluxi; Chen, Lei

As can be seen from the analysis of Fig. 12 , when the RD is 0, the wind speed at 40 m is well amplified, and the wind speed amplification factor tends to 1. After 40 m, the overall wind speed is blocked, so the wind speed amplification factor is very low. When RD is 1, the WVA at 60 m is similar to that when RD is 0, but at this time, the fluctuation range of the wind speed amplification factor is increased. When RD Li and Chen / Building Simulation / Vol. 13, No. 2 432 is 2, the distribution of the opening is more dispersed, and the fluctuation range of the wind speed amplification factor is further increased. The wind speed within the height of 80 m is fluctuating. As the number of RD enhances, the numbers of wind shadow areas further increase. Nevertheless, even if the wind shadow area is increased, the wind speed amplification factor of the upper wind shadow area is far larger than the far end. Figure 13 shows that in the case where the upper end is open, the change in the wind speed is almost opposite to the lower end opening. When the RU is 1, the average value of the wind speed amplification factor is the largest, and the fluctuation amplitude is relatively small, because that the hole dispersion degree in this case is moderate, and the influence range is large with a larger wind shadow area. When the lower end is open, it can be seen that the mean wind speed amplification factor is the same when RD is 1 and 2. But for case RD1, the overall distribution is more uniform and the fluctuation amplitude is smaller. Therefore, when RD is 1, for the lower end opening, the wind environment is the best, which is conducive to building energy conservation and heat loss. Along this vertical direction, z represents the height of testing point and H indicates the building height (Fig. 14) . When CR value is larger than one, the better the pollutant dispersion situation (Figs. 14, 15 ). Following observations can be made:  With the number of voids increase, the air contaminants disperse more efficiently. The best pollutant dissemination condition is achieved when the holes almost completely distribute along the building i.e. case 9A. This is mainly because that the air pollutants locating at the leeward of building can be flowed by the wind through the hollow areas. Consequently, more construction voids can promote efficiently the loss of pollutants situating downstream of the building. For example, in cases of A7 and A9, all CR values are under 0.5 which is apparently smaller than the averaged CR value of 2.38, 2.11 and 1.27 for cases A0, A3 and A5, respectively.  The distribution of air contaminants is related to the building voids positions. The distance between hollow areas on the building could significantly influence the pollutant gathering situation in the leeward of construction. For distance between holes on building larger than twice height of holes such as case B3, the pollutant gathering effect at the behind of gap between voids enhances increasingly by enlarging the distance between holes. On the other hand, it should be noted that for cases B0 to B2, air contaminants behind the gap between holes could also be dispersed effectively. For example, CR values of 0.7 and 1.8 for case B2 at the height of z/H being 0.3 and 0.7 are much lower than that under same height for cases B3 and B4 which are 4, 5, 4, 5 respectively.  For wind flow condition of hollow volumes where position at the end of building (case C), the discretization of