A Comparative Study Of UAV-based Building Flow Measurement And Wind Tunnel Test Results

With the continuous development of my country’s economy,the number of highrise buildings in the city is increasing,and the distance between the buildings is decreasing.Accurately obtaining the changes of the wind field around the building is very necessary for the wind resistance design of the building and the improvement of the urban wind environment.The traditional method of measuring the wind field has certain limitations for obtaining the wind field information around the building.For example,due to site constraints,multiple wind measuring towers cannot be erected around the building at the same time,and lidar is expensive and susceptible to building interference.Therefore,this paper proposes a method based on a six-rotor UAV equipped with an anemometer to conduct the on-site measurement of the flow around the building.The flexibility,simplicity and accuracy of the UAV wind measurement provide an effective method for the on-site measurement of the flow around the building.means.This paper further illustrates the feasibility of UAV equipped with anemometers for wind measurement and the wind characteristics of typical buildings by comparing the field measurement with the wind tunnel test.The work done in this paper is as follows:Firstly,based on the existing domestic and foreign research results,the wind tunnel test is carried out to study the accuracy of the wind measurement of the UAV equipped with anemometers.Factors such as the self-inclined angle and the rotation of the rotor formed by the UAV resisting the wind will affect the measurement accuracy of the anemometer.Therefore,the most reasonable installation height is determined through the wind tunnel test to reduce this adverse effect.The comparison of the data collected by the anemometer on the six-rotor UAV and the data collected by the wind tower shows that the data obtained by the corrected UAV is close to the data from the wind tower,and the errors of wind speed and turbulence are within ±3% and ±5%;the gust factor,turbulence integral scale and fluctuating wind speed power spectrum law of the two are relatively close.Then,based on two sets of unmanned aerial vehicle wind measurement systems,the wind characteristics of the wind field around typical buildings in the Haikou measurement site were measured,and the inflow wind profile was fitted based on the corrected measured data.According to the inflow wind profile fitted by the measured results,the area is between the C-type landforms and the D-type landforms in the relevant Chinese norms.The measured building height is 82.45 m.The on-site measurement results show that the wind field characteristics of the 60 m and 80 m height planes are significantly affected by the building.The affected areas are mainly distributed in the areas near the two sides of the building and the wake area of the building.Compared with the incoming flow,the average wind speed decreases,the downwind and crosswind turbulence increases compared with the incoming flow,the integral scale of the downwind and crosswind turbulence decreases compared with the incoming flow,and the gust factor in the downwind and crosswind directions increases compared with the incoming flow.The peak value of the pulsating wind speed power spectrum in the downwind and crosswind directions in the area affected by the building has a tendency to move to the high frequency band;the field measurement results at the height of 100 m and 120 m show that the wind field characteristics of these two planes are less affected by the building.Finally,based on the scale ratio of 1:150,the wind tunnel test was carried out on the wind field around the typical building,and the wind tunnel test results were compared with the measured results.The wind tunnel test and the measured results show that the general trend of the plane wind characteristics is basically the same,and the distribution of the affected areas is roughly the same;both affected areas are mainly distributed in the areas on both sides of the building and the wake area of the building;The mean wind and turbulence integral scales both have a decreasing trend,while the turbulence degree and gust factor have an increasing trend.The peaks of both fluctuating wind speed spectra have a trend of moving to high frequency bands.However,due to the instability of the natural incoming wind speed and wind direction during the actual measurement,the data collected in the actual measurement has greater discreteness,and the local modeling of buildings and other factors,the actual measurement results have greater volatility than the wind tunnel results.