The Research On Resistance Property Of Natural Ventilation Induced By Wind Force

Reasonable utilizing natural ventilation has important significant in saving buildings energy and improving IAQ. Firstly the article summarizes several main fields and current situation of natural ventilation research, and points out that the fluid mechanics of cross-ventilation with open windows are completely different from those of air infiltration through cracks and pipe flow. Thus the traditionally method of evaluating natural ventilation flow rates is under suspicion. Then the author uses the method of CFD to simulate the virtual stream tube passing though large openings and around building in boundary-layer atmosphere.The turbulent models and the methods of calculation for numerical simulation are summed up. And the same time how to deal with the obstruct region and the boundary condition are summarized.Though simulating the pressure distribution on the sealed building, it can get the abundant messages about the pressure distribution on the windward wall and the leeward wall. Thus we can learn that the pressure values on the windward face are inconsistent. So we think that it was not in reason to use mean pressure in traditionally calculating the flow rates.It is the first time to detailed simulate the virtual stream tube passing though large openings of several cubic buildings with different areas and relative position of the openings in boundary-layer atmosphere.Through simulating the steam field of the building with different opening configuration. It is observed that a kind of stream tube is formed through the building. It becomes clear that a major part of dynamic energy is preserved until outside the room and how much the energy changed around the openings. And it is the foundation to analyze the resistance properties of cross-ventilation.Through simulating the pressure distribution on the facade of the building, it can be found that the much pressure change on the sealed building only happened in and around the openings when airflow pass through the building and the openings area is in some proportion to the facade area. So we think it is only the pressure in the range of opening position inducing the air passing through the building. That it is need to use the pressure on the sealed building in the opening position for calculating the natural ventilation airflow rates is proposed in the first time.The resistance properties of the natural ventilation though several cubic buildingswith large openings in different models are detailed simulated and analyzed. We can compare and analyze the difference of the resistance properties when there are different relative opening areas and positions. Thus the factors influencing the airflow rates can be found. And the same time it is explored how to calculate the natural ventilation flow rates.