Experiments And Numerical Simulation Of Outdoor Wind Environment And Natural Ventilation

Wind environment includes two interrelated part, outdoor's and indoor's. With the growing number of high rise buildings and the increasing building density, the wind environment becomes an imporatant factor in deciding the quality of life. On one hand, the quality of wind environment around buildings has significant effects on pedestrian comfort even safety. Consequently, it is important for wind-environment optimization by arranging the buildings reasonably.On the other hand, wind-environment assessment has been a critical issue in the design of green building and research on it will contribute to the wind environment analysis systematization and theorization. Sorts of means were developed but not well compared, and it leads to the arbitrariness during the process of selecting method. Therefore, the study on the comparison of three prevailing methods was conducted herein, for the purpose of providing theoretical support as well as practical experience in determination of a relatively reasonable means with corresponding criterion. Compared to mechanical ventilation, natural ventilation could save energy, reduce pollution and meet demands of human comfort. In order to explore its potential, it was practically valuable to study the single room ventilation affected by multiple factors and suggest the empirical formula.On the study of the pedestrian level wind environment, the dimensionless layout parameters of residential quarters with parallel layout were firstly designated in order to facilitate the application of the research findings. Then, a series of wind tunnel tests on the flow fields so as to access to the overall status of the wind environment were designed and conducted. By studying the relationship between wind-velocity-ratios, layout parameters and wind direction angles, various wind-velocity-ratio contours which are easy to be applied in actual cases were achieved. Based on these studies, two optimization design ideas and given examples on how to apply the contours in wind-environmental optimization are addressed. Those contours based on the two optimization design ideas facilitate the optimization and pre-evaluation on wind environment for proposed buildings. Meanwhile, in order to obtaining the pressure distribution on the buildings for analysis, numerical simulation for the buildings mentioned above was carried out by using the Reynolds averaged equations and the RNG k-εturbulence model. By changing the distance between adjacent buildings and the orientation of these buildings, we can get the influence to the pressure distribution of the two elements stated above. On the study of wind environment assessment methods and citeria, firstly, the general expressions of those methods were formulated respectively, and correspondingly theoretical comparisons and analyses were conducted. Then, in terms of an actual building with corresponding wind records, the comparison of the results those obtained by applying various assessing methods was also achieved. Finally, a novel index for assessment via threshold-of-probability-of-exceedance method was developed to indicate the strictness of the criteria developed in the recent years, and this work provides a theoretical tool to homogenize the wind environment criteria in the future.On the sudy of indoor ventilation, This paper analyzed the impact of wall porosity, the pressure difference between windward and leeward, inlet and outlet area ratio and the relative position of windows on windward and leeward through a series of wind tunnel experiments in association with numerical simulation. The influence regime of these factors to natural ventilation was thus concluded. Whereby, the empirical formula that described the relationship among the flow rate, wall porosity, and wind pressure difference was achieved. Furthermore, the influence of inlet and outlet area ratio and the relative position of indoors on windward and leeward were reflected in the improved formula. The empirical equation proposed herein provides a quantitative method on indoor ventilation design for buildings. Finally, the analysis revealed that it was inappropriate to regard the discharged coefficient as constant and the reasonable value was suggested by the author.The results calculated by the suggested discharged coefficients was equivalant to the value calculated by the empirical formula.