Investigation Of The Wind Flow Characteristics And Wind Energy Distributions Over The Rooftops Of Tall Buildings

The world’s energy shortage is increasingly prominent.Oil,coal and other traditional energy use will inevitably cause environmental pollution.Wind energy as a clean renewable energy is easy to use and cost-effective.The development of wind energy can alleviate the above problems to a certain extent.At present,research on the roof wind field and wind energy mostly concentrates on standalone buildings,whereas few studies about different building sizes are conducted.For the complex flow fields over rooftops of tall buildings,numerical simulations encounters difficulty in accurate predictions.In this study,wind tunnel tests on wind flow field and wind energy over rooftops of buildings with different sizes are conducted.Wind flow characteristics and wind energy distributions on the roof together with the deployment strategy are discussed according to the wind tunnel test results.The characteristics of wind fields in different areas of the roof of a tall building were important references for the installation of wind turbines,and were examined in detail in this study.Wind speed ratio,turbulence intensity ratio,and inclination angle were defined,and the variation of wind field characteristics along the height is analyzed for nine locations on the roof.The results showed that the wind speed ratio in the region close to the roof was small and the turbulence intensity ratio was large at wind directions of 0° and 22.5°.When the incoming wind direction increased to45°,the wind speed ratio at the bottom of the measurement point increased sharply,whereas the turbulence intensity ratio decreased sharply.The measurement points of the parallel incoming wind direction show the most prominent performance.In order to study the building size effect on the wind field over rooftops,building models with height ratios of 1.5,2.5 and 3.5 and width ratios of 1,2 and 3were used.The results showed that the wind speed ratio at locations close to roof increased as the building height ratio increased.Turbulence intensity ratio increased as the building height ratio decreases.Width ratio and height ratio demonstrated the opposite effects.When the building width ratio increased,the wind speed ratio at locations close to the roof decreased,whereas the turbulence intensity ratio increased.The maximum wind speed ratio,minimum turbulence intensity ratio and the corresponding height changed with the building sizes.The results showed that the maximum inclination angle was more sensitive to the width ratio than the height ratio.This study discussed the wind flow characteristics of wind energy distributions on roofs based on the results of wind tunnel tests.The wind energy distributions on the roof of tall buildings were evaluated by defining the area-weighted average wind energy amplification factor.The effects of different roof areas,building height/width ratio and wind angle on the wind energy distributions over the roof were analyzed and summarized.It was found that the maximum area-weighted average wind energy amplification factor on the roof could reach 1.58,which corresponded to a height ratio of only 1.07.This indicated that wind turbines could capture large amounts of wind energy even in areas close to the roof.And based on the corresponding wind turbine installation specifications,the wind energy distribution of each wind turbine installation height of different building models was studied,providing some basis suggestions for the deployment of wind turbines.