Field Measurement And Numerical Study On Spatial Characteristics Of Wind And Rain In Cluster Buildings

The process of urbanization has changed the near-earth atmospheric structure and formed a local climate dominated by urban effects,which has led to a series of problems such as pollution aggregation,heat island effect,and poor building environment.Wind and rain as the most common natural phenomena can effectively eliminate or improve the adverse effects of these problems.Therefore,accurately grasping the spatial movement and distribution characteristics of wind and rain has become the necessary basis for carrying out quantitative research on these problems,and it is of great significance to realize the development goal of ’ green city ’.At present,domestic and foreign scholars have carried out relevant research on the distribution characteristics of wind and rain,but more concentrated on the wind-driven rain distribution of isolated single building walls,and the related research on the spatial motion and distribution of wind and rain in complex environments is still lacking.Urban buildings are mainly characterized by cluster layout,with dense distribution,variable shape and staggered height.Compared with the peripheral areas of the city,due to the interference effect in the internal area of the cluster layout,the movement and distribution of wind and rain space are more complex.Using the measured and numerical methods to study and master the relevant characteristics and laws will effectively promote the research in related fields.In this paper,the measurement and numerical simulation of wind and rain spatial field are carried out based on the layout of cluster buildings.The main work is as follows :(1)By using the relevant wind and rain measurement equipment and the national meteorological data platform,the measured points in the urban area are selected to carry out the monitoring and collection of wind and rain information.Combined with the data of meteorological stations outside the city,the spatial wind and rain fields of the layout of cluster buildings are analyzed.The results show that the cluster interference effect of urban buildings will significantly affect the wind field.During the monitoring period,the wind speed of the measured points in the urban area is significantly reduced compared with that of the stations outside the city,and the daily average wind direction distribution is more concentrated.The rainfall intensity recorded at the measured points in the urban area is usually not synchronized with that at stations outside the city.For the small area where the two measured points are located in the urban area,the spatial distribution of wind and rain fields is also different due to the interference of surrounding buildings.The wind directions of the two measured points are consistent only on the side of less buildings,and the accumulated rainfall at the measured points at the lower position is slightly larger.(2)For the two measured points in the cluster building layout environment,the appropriate short-term wind field samples and specific rainfall events are selected to analyze the wind characteristics and the distribution of rainfall microphysical quantities at the measured points,and the Euler multiphase flow model is used to simulate the specific wind and rainfall events.The results show that the fluctuation characteristics of the wind field at the measured points are relatively intense and positively correlated with the complexity of the distribution of the surrounding buildings.The turbulence intensity,gust factor and other fluctuation parameters increase with the increase of the average wind speed,and the wind speed power spectrum is prone to deviate at high frequencies.The high wind speed will lead to the breakup of raindrops,leading to the dominant number of small raindrops at the measured points with high wind speed;however,the number of large-size raindrops plays a decisive role in parameters such as rainfall intensity and liquid water content.There are differences between the measured urban spatial raindrop spectrum and the standard M-P spectrum in some intervals,and the M-P spectrum underestimates the concentration of large particle raindrops.(3)Aiming at the difference of building layout,four typical building cluster layouts are designed to carry out wind and rain field simulation research.By determining the relevant simulation boundary and parameters,the spatial motion and variation characteristics of wind and rain in buildings under specific wind speed and rain intensity are simulated and studied.The results show that in the building group,with the increase of the number of semi-high buildings,the wind field will be isolated and the vortex scale will be reduced.The droplet velocity of small particle size is easily affected by the wind field,and it is concentrated in the position with large wind speed;the difference in volume proportion of raindrops with the same particle size at the same height before and after the building group is up to 16.08 %.