Flow Visualization and Inflow Direction Measurement at a Cross-Ventilated Large Opening

In the case of cross ventilation through a large opening, it is well known that the inflow direction at the opening is not normal to the opening. A simplified prediction method for simultaneously predicting the inflow direction at the inlet opening and the airflow rate is presented. It is also well known that the use of general discharge coefficient values (CD) is not suitable for the calculation of cross ventilation rate. The first reason is that the simple connection of the pressure loss coefficient of an opening (? as the reciprocal of square CD) in series, under-estimates the airflow rate. Secondly, CD varies according to the wind direction and the use of normal values over-estimates the airflow rate. Therefore, the proposed method uses the total pressure loss coefficient of the room (?) instead of ? (or CD). Flow visualization was conducted under various conditions using a simple room model and showed the basic flow characteristics at the inlet opening. Wind tunnel tests using a three-storey apartment building model with a movable test room were conducted to investigate the inflow direction and the airflow rate. The combination of room positions and external wind directions results in various inflow directions at the inlet opening.