Comparative Study of the Effect on Outdoor Wind Environment by High-rise Buildings Layout Types

The existing study of urban thermal environment focuses on the urban morphology for urban scale,which does not take full account of the effect of the thermal environment and especially wind environment of the layout of the buildings form for the small-scale area and non-homogeneous distribution.Numerical simulation was carried out to investigate the wind environmental state around a building group consisting of six rectangular high-rise buildings by using the Reynolds averaged equations and the renormalization group(RNG) κ-e turbulence model.The six buildings were initially arranged into two rows and three columns.Six types of building group with different layouts were obtained by altering the distance between two adjacent buildings in each column.The wind-velocity ratios and the corresponding velocity vector field around each type of building group at pedestrian height level(1.5 m) were then examined and compared with each other.The average outdoor air flow of X-shape is the weakest among all layouts,which is unfavorable for ventilation.The variation of measure points' wind velocity near windward endpoint of buildings in O-shape is comparatively slow.In addition,this layout has the minimum wind velocity at outlet position.These show that O-shape layout has the least wind tunnel effect on outdoor wind environment.Compared with H-shape and O-shape,Y-shape with windward concave,can improve the wind velocity of outlet position.However,if the concave continues to be widened and changes into V or U-shape,the wind velocity of outlet position will decrease.To go further,the study quantifies the concave shape,trying to seek the link between the concave shape and wind velocity ratio of the outlet.The relationship between the x,which is concave coefficient and the y,which is wind velocity ratio at outlet position can be described as a polynomial function.In the end,the study proposes that,in Y,U and V-shape layouts,when the initial wind direction reverses during summer and winter,there are some measure points having comparative difference on wind velocity in two seasons.When designers plan the outdoor landscape,especially in making choice of the green or pavement,these points need detailed design to enhance ventilation in summer and reduce air flow in winter.