Full Scale Assessment Of Performance Of Windcatcher System Using Numerical Methods

This paper employs numerical methods to study and analyse the overall performance of windcatcher system which is a new pattern of natural ventilation and main factors affecting the performance. The proper mathematical models of windcatcher system with square section and circlar section have been built and the numerical method has been chosen by comparing the simulation results of the grid number, turbulence model etc. The simulation results show a good agreement with the experiment.The windcatcher was divided internally into four segments for the purpose of air supply and extract, but determining the action of these segments was difficult for experiment. So numerical method has been applied to get the velocity of four segments and then solve this problem.The main factors affecting the performance of windcatcher system have been investigated by building great deals of models. The simulations have carried out for the wind velocity v in the range of 0.5~10m/s, the wind angle a of 0° -45°, the louver angle β of 15° -90°, the louver layer k of 2-8 and the louver length / of 0.2~1m. The results indicated: 1. the the air exchange rate ACH increase with v and a when a>15°. When v=1m/s, the minimum ACH is 7.4; 2. the performance of square windcatcher system is always better than the circlar one with the equal section area. 3. the volumetric airflow increase with either β or k or l. But the growth rate of volumetric airflow will become slower along with β and kTaking advantage of the simulation, the supply air uniformity, the air velocity distribution in the test room and the short-circuiting flow have also been investigated. The results show that the external wind angle a has a bigger influence on the square windcatcher. The supply air uniformity and indoor air velocity distribution will become better with the increase of a. But the short-circuiting flow will become worse when a raises.The regression analysis has been applied in the calculation of the supply air volume in a creative way. The factors having important influence on the performance of the windcatcher system and the supply air volume have been analysed. The relations between the air supply volume and the wind speed, wind direction and louver angle, the louver layers, the louver length is linear, cubic polynomial, quarternary quantic and parabolic respectively.