Study On Calculation Method Of Ventilation Rate And Large Eddy Simulation Of Residential Buildings

Natural ventilation can create a comfortable indoor environment and greatly reduce the air conditioning time,which has significant advantages in creating a healthy indoor environment and reducing building energy consumption.Through the review of natural ventilation research at home and abroad,it is found that the measurement data of natural ventilation in real environment is insufficient,several existing ventilation calculation models are proved to have large errors,and the large eddy simulation method for indoor and outdoor flow field of buildings is not mature,which all restrict the research of residential natural ventilation.The purpose of this study is: 1)to obtain the spatial and temporal data of natural ventilation in real residential environment,2)to improve the accuracy of ventilation rate calculation model,3)to study the large eddy simulation method of indoor and outdoor flow field of real environment buildings.These provide support for the measurement of residential natural ventilation,the development of calculation model and the research of large eddy simulation method,and promotes the research of residential natural ventilation characteristics.Therefore,through the field measurement,theoretical analysis and numerical simulation methods,we obtained comprehensive experimental data,developed a more accurate model,and studied the boundary setting method of large eddy simulation for indoor and outdoor flow field of real buildings.The main conclusions are as follows:(1)single-sided natural ventilation of urban residential buildings is dominated by thermal pressure,while cross ventilation is dominated by wind pressure.Compared with the commonly used methods in laboratory,wind tunnel and numerical simulation,tracer gas attenuation method,wind speed area method,pressure difference method and reference position wind speed method,the measurement error increases in turn.(2)Compared with the experimental results,the average error of our model is 13%,and the calculation accuracy of existing calculation models is improved by 11%.Compared with the existing model,the calculation error of the improved model is decreased by 27%.(3)According to the measured three-dimensional wind speed series,the grid scale and time step of large eddy simulation were calculated,and the effects of different inlet boundary setting methods(average wind speed,discrete wind speed,average wind direction,fluctuating wind direction,turbulence generation method,etc.)were compared.The relative errors of different inlet boundary setting methods and experimental measurements are analyzed.It provides a basis for the determination of the important influencing factors and the setting method of the inlet boundary conditions in the large eddy simulation of the indoor and outdoor flow field of the environment buildings.(4)Based on the three-dimensional wind speed measurement,the unsteady and unidirectional flow characteristics of natural ventilation were analyzed.The ventilation volume between households is calculated according to the three-dimensional wind speed and the ventilation volume measured by the tracer gas attenuation method.Combined with the fluctuating flow field information obtained by large eddy simulation,the instantaneous flow field of natural ventilation and the unsteady flow characteristics of multi zones cross ventilation were analyzed,which lays a foundation for the research on the unsteady characteristics of natural ventilation of urban residential buildings.