ABSTRACT
The point of how to improve the product of greenhouse is to improve greenhouse environment control. Then the key factors of greenhouse environment, such as ventilation, airflow, temperature, humidity and so on, should be clearly known to us. But wind tunnel test is difficult to conduct because of the large size of modern commercial greenhouse. Since numerical simulations offer a detailed picture of the temperature spatial distribution and the airflow field, it became a powerful tool for simulating the complex greenhouse environment. The first computational fluid dynamics (CFD) simulations for studying greenhouse ventilation were carried out by Okushima et al.(1989), who compared this numerical method with the wind-tunnel results of Sase et al.(1984). Even though their results only weakly agree with the experiments, they obtained important information on flow patterns inside the greenhouse. In recent years, CFD plays more and more significant role in the field (Mistriotis A., et al., 1997). CFD codes were used in both closed greenhouse (Boulard et al., 1997; Lamrani, 1997), ventilated greenhouses (Mistriotis et al., 1997, Boulard et al. 1999) and greenhouses equipped with insect-proof screen (Bartzanas, T. et al., 2002; Fatnassi, H., et al., 2006). Moreover, for it can offer the temperature spatial distribution and the air velocity field, the CFD numerical simulation is conducted to investigate the different influence on the environment inside the greenhouse with different equipment and controlling methods, such as natural ventilation, insect-proof screen, plastic tunnel, sawtooth-type roof with multi-span and so on. Some progress in flow modeling by computational fluid dynamics (Mistriotis et al., 1997) and in airflow measurements has been made for a closed greenhouse (Boulard et al., 1999), a two-span naturally ventilated greenhouse (Boulard et al., 1997; Wang et al., 1999), a multi-span sawtooth greenhouse (Kacira et al., 1998) and a multi-span Venlo-type greenhouse (Wang and Boulard, 2000).
