Study On Ventilation Characteristics Of Pulsating Natural Wind Building

At present,effectively reducing building energy consumption has become an important task of energy saving and emission reduction.Natural ventilation technology is the most direct way to reduce energy consumption in building operations.This technology uses natural wind to improve the indoor thermal and humid environment in the transition season,while ensuring good indoor air quality,thereby reducing the application of artificial air conditioning and achieving energy saving.Natural wind has pulsating characteristics.Previous studies on natural ventilation of building wind pressure have used constant uniform wind.Many studies have shown that pulsating natural wind and constant wind has different ventilation effects,but the quantitative study on the difference has not been reported.This study focuses on the pulsatility of natural wind and quantitatively studies the possible impact of natural ventilation on building wind pressure.In this study,a three-dimensional ultrasonic anemometer was installed at a height of 10 m in an open factory in xi ’an,and natural wind speed data collection and meteorological monitoring were carried out for two years.Based on the statistical analysis of the test data,the wind speed characteristics and wind direction law of the measured natural wind were analyzed.On this basis,a numerical model of natural ventilation of wind pressure in a single room was established according to the pulsation and size rule of measured wind speed The effect of dynamic natural wind speed pulsation characteristics(pulsation period,pulsation amplitude)on the natural ventilation effect of the building was studied.Based on the analysis of natural wind frequency distribution,a two-parameter Weibull distribution model and Markov model were combined to predict the time course of natural wind speed.Based on the measured natural wind data in xi ’an area,the wind speed time path with a time step of 1 s and a time interval of 1 h could be predicted by using this method.By comparing the frequency distribution,autocorrelation,average wind speed and standard difference between the predicted natural wind speed and the measured natural wind speed,the reliability of the wind speed prediction model was verified.Compared with other natural wind speed time series construction methods.The wind speed prediction method could be constructed based on the average wind speed value to obtain the natural wind speed time series corresponding to the average wind speed value.In addition,when predicting the wind speed,the time step was smaller,and the wind speed characteristics were more comprehensively reflected.Finally,Fluent 17.0 was used to simulate and calculate the naturally ventilated buildings under the unsteady flow field,the time series of the natural wind wind speed predicted by the two-parameter Weibull distribution model and the Markov model were brought into the calculated wind field using UDF,which was used as the entrance boundary condition for large eddy simulation.At the same time,the steady-state natural ventilation under the same average wind speed was numerically simulated to explore the difference between the constant wind and pulsating natural wind ventilation effects.The results showed that the difference between the pulsating natural wind and the constant wind ventilation effect was related to the average wind speed value.When the average wind speed was less than or equal to 0.5 m/s,the pulsating natural wind ventilation effect was worse than the constant average wind.When the average wind speed value was greater than or equal to 0.8 m/s,the pulsating natural wind ventilation effect was less than the constant average.The greater the average wind speed,the greater the difference in ventilation effects.The purpose of this paper is to help the reliable prediction of the ventilation effect of natural air pressure in buildings.