The Study Of Flow Rate Model Of Single-sided,Wind-driven Natural Ventilation In Buildings

Natural ventilation is an energy-saving,environmentally friendly passive technology.The application form of natural ventilation can be mainly divided into single-sided ventilation and multi-sided ventilation(cross-ventilation).Although the cross-ventilation is widely used,due to the issue of room size,personal privacy protection and fire protection,single-sided ventilation model has also been widely used in the general office or apartment buildings.Natural ventilation system of the building can be divided into wind pressure and thermal pressure ventilation systems by driving forces.The thesis focuses on the study of single-sided natural ventilation driven by unsteady wind pressure,the average ventilation rate and fluctuating ventilation rate are analyzed.Combining with the numerical simulation method,three different types of natural ventilation buildings are studied,and a new flow model is put forward.Firstly,for the case of the opening in windward,this thesis analyzes the average flow rate and fluctuating flow rate under the wind pressure,and focuses on the study of the fluctuating ventilation rate and the broadband ventilation rate in the fluctuating flow,and the average flow model is combed by the measured data of the natural ventilation,then a total ventilation rate model is put forward.RNG model and LES model are used to calculate and analyze under different opening ratios.The simulation results show that,the natural ventilation is mainly based on the fluctuating ventilation when the opening ratio is small,and the fluctuating ventilation should be taken as the actual ventilation rate.When the opening ratio is large,the ventilation rate is mainly based on the average ventilation rate,and the opening ratio of the boundary can be 3% for reference.In addition,when the flow velocity fluctuation is larger than the average velocity,the ventilation rate is the sum of the average ventilation rate and the broadband ventilation rate.In the thesis,the RNG and LES simulation results are compared,and the applicability of the model is analyzed.The influence of the relevant influencing factors on the flow rate is simulated and analyzed.Secondly,for the case of the opening in the leeward,the thesis summarizes the exponential relationship between the ventilation rate and the open area,and the linear relationship with the wind speed,and a single-opening ventilation calculation formula is deducted for the leeward case.For parallel ventilation,this thesis mainly studies the dimensionless ventilation,it is found that the dimensionless ventilation of the shear layer is a fixed value when the opening area is constant,but the opening ratio will have some influence on it.The ventilation rate of the shear layer is exponentially related to the open area and linearly related to the wind speed.In addition,through the integration of the data,the calculation formula of the shear layer ventilation is derived.Finally,the ventilation of three cases is compared,and the results show that when the opening is located on the windward side of the building,the ventilation rate is the largest.Furthermore,it can be seen from the linearization process,regardless of the position of the opening,the influence of the opening ratio on the ventilation volume is greater than wind speed.In this thesis,the ventilation model is put forward by theoretical analysis and numerical simulation,and the flow field analysis is carried out for different forms of single-sided natural ventilation.These results have some guiding significance for natural ventilation design and evaluation.