Research On Wind Profile Of Building Wind Field Based On Experimental Data

With the intensification of urbanization and the increasing energy demand in the city,the utilization of wind energy in the urban building environment has become one of the effective methods to alleviate the urban energy shortage.However,for the micro-site selection of roof wind turbines in the building environment,field measurement combined with numerical simulation or wind tunnel experiments is an effective method.However,in order to simulate and experiment more accurately the complex wind field characteristics of the building environment,it is necessary to accurately describe the inflow wind profile of the building environment.Therefore,the research on the accurate expression of the vertical variation of wind speed in the building environment by the inflow profile is the first key problem to be solved in the development of wind turbine micro-siting methods based on CFD or wind tunnel experiments.In view of the above problems,this paper uses the field measurement method to study the inflow wind profile in a building group in Hohhot,and provides some theoretical and experimental support for the micro-siting of wind turbines and the evaluation of wind resources in the building environment.Firstly,in order to determine the expression of the atmospheric wind profile that fits the building environment,this paper identified three types of wind speed profile parameters based on the terrain features of the experimental site.For the power law wind speed profile parameters,three methods were used to obtain the wind shear exponent,including the selection of ground roughness category,least squares method calculation,and formula transformation calculation.For the logarithmic wind speed profile parameters,the displacement height Z_d and the roughness length Z₀ were determined through the morphological measurement method Rt and the Ma method,respectively.In addition,the effective average height of the building for the semi-log wind speed profile parameter,H_e-ff=8.18m,was calculated based on the building size.Furthermore,the accuracy of the three wind speed profile expressions was compared and analyzed based on the measured wind speed and its statistical parameters.The results showed that the logarithmic wind speed profile with Z_d=4.68m,Z₀=0.718m,and U*=0.268m/s was more consistent with the experimental wind speed profile and the established logarithmic wind speed profile was more suitable for describing the wind speed profile in the building environment.Secondly,in order to obtain the actual wind speed profile characteristics in the building environment,this paper analyzes the wind speed distribution probability at 11 m of the experimental site to divide different wind speed conditions.Then,based on the 11 m wind direction,the wind direction deviation at each height is analyzed,and the variation characteristics of the prevailing wind direction and the actual wind speed profile under high wind speed（U_b>4m/s）are determined.Based on the results obtained,the actual wind speed profile and the two established wind profiles are further compared and analyzed.The results show that it is feasible to establish the inflow wind speed profile with constant wind direction under the condition of high wind speed U_b>4m/s.When U_b>8m/s,the PL wind shear index converges to 0.22,which is more consistent with the P-LG（LOG）wind profile.However,it is found that the measured wind speed tends to be far away from the wind profile at a higher height（z>100m）.Compared with the case of U_b>8m/s,the measured wind speed deviates more from the PL and P-LG（LOG）wind profiles under the condition of U_b>4m/s.It shows that the approximation degree of wind profile and actual measured value is affected by wind speed.When the wind speed is large,the wind profile expression is more consistent with the measured value.Finally,in order to evaluate the performance of the measurement-correlation-prediction（MCP）method in the accuracy of wind speed profiles in the building environment,the accuracy of the two prediction methods at different heights and the influence of data time span on the prediction results are analyzed.In this paper,the wind speed of the experimental site is predicted by the variance ratio method and the LSTM method using the wind data of the reference site 55 km away from the experimental site.The predicted values were compared with the measured daily maximum wind speed and annual average wind speed,and the average wind speed test factor M and the statistical parameter RMSE were used to evaluate the accuracy of the prediction results.Finally,the wind speed profile expression established by the MCP method is analyzed.The results show that the prediction accuracy of the LSTM method in the building ring is better than that of the variance ratio method,but as the height increases,the accuracy of both methods will decrease,which is related to the principle of spatial correlation.In the LSTM method,the prediction results based on spring data are the most accurate.Through the analysis of the short-term wind speed prediction results,the prediction results based on the measured wind speed in three months are the most accurate,while the data based on one month and one week are difficult to accurately predict the long-term measured wind speed.In addition,it is found that the second method based on MCP method can achieve more accurate wind speed profile establishment,but the time span of short-term wind speed data should not be less than 3 months.