Comprehensive validation of experimental and numerical natural ventilation predictions based on field measurement with experimental house

Abstract

In this study, field measurements of the natural ventilation rate of an experimental house with a symmetrical plan and two openings in the east-west direction were conducted under various external wind direction conditions. A constant injection tracer gas flow technique was used to evaluate the ventilation rate. The 10-min average indoor concentrations and velocities at the centres of the openings were measured and analysed according to each wind direction. Following this measurement, wind tunnel experiments (WTEs) and computational fluid dynamics (CFD) simulations with a steady Reynolds-averaged turbulence model were also performed to compare their prediction accuracies against that of the field measurement data. The results show that the mean values for the velocity and concentration obtained from the WTE and CFD generally agreed with the field measurements for many wind directions. However, the WTEs and CFD simulations overestimate the concentrations (underestimate the ventilation rates), especially in the south and north wind directions perpendicular to the opening direction, and the extent of this overestimation is particularly pronounced for the CFD simulations. The prediction accuracy of the CFD simulations may be improved by using a turbulence model that considers the large-scale fluctuations of airflow around the building. However, the main reason for the overestimations by both CFD and WTEs in these wind directions was that the unsteadiness of the external wind direction during the averaging time was not well considered in these methods. This might be the next issue to be solved for more accurately reproducing the actual ventilation rate.