AIRFLOW CHARACTERISTICS OF CROSS VENTILATION THROUGH DIFFERENT OPENING CONDITIONS

摘要

The purpose of this study was to clarify the differences in airflow characteristics outside and at three points in a cross-ventilated room under six opening conditions: window-open; insect-screen: lace-curtain; fabric-curtain;combined condition with insect-screen and lace-curtain; and combined condition with insect-screen, lace-curtain and fabric-curtain. The air velocity was measured by four ultrasonic anemometers, during the summer of 2004.The airflow fluctuation of cross ventilation was analyzed from the viewpoints of turbulence statistical parameters,power spectrum, etc. The following results were obtained: (1) The mean air velocities were the fastest at the windward point and further decelerated at the center point. The ratio of power spectrum in the frequency range of less than 0.1Hz was the lowest point at the windward point and lower at the center point where the flow section area became larger and the airflow was diffused. The air velocity and power spectrum in low frequency range were mostly decelerated and higher at the leeward point, and accelerated and highest at the path point where the flow section area became smaller and airflow was contracted. The similar trends were kept under any opening conditions; (2) The mean air velocities under the window-open condition showed higher values and were similar with ones under the insect-screen condition at any points. However, they were different from ones under the combined condition with insect-screen. lace-curtain and fabric-curtain; (3)The differences in characteristic length scale of eddies according to opening conditions proved the largest values at the windward point and the smallest values at the center point; (4) The negative slope and the power spectrum ratio in the low frequency range showed the highest values at the path point.