Teitel, M., Institute of Agricultural Engineering, Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan, 50250, Israel
Dvorkin, D., Institute of Agricultural Engineering, Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan, 50250, Israel
Haim, Y., Institute of Agricultural Engineering, Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan, 50250, Israel
Tanny, J., Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan, 50250, Israel
Seginer, I., Faculty of Civil and Environmental Engineering, Technion, Haifa, 32000, Israel

The use of screens to reduce insect entry into greenhouses has become a common practice. Screens act as mechanical barriers that prevent migratory insects from reaching the plants. However, they impede ventilation thereby increasing air temperature and humidity within the enclosures. In an attempt to explore ways by which ventilation can be improved, the effect of screen inclination on flow parameters downstream the screen was investigated experimentally and by computational fluid dynamics (CFD) simulations. Experiments were done in a wind tunnel and CFD simulations were conducted by using the ANSYS-CFX 11 software package. The CFD code was first validated by comparing between the numerical and experimental velocity profiles downstream inclined screens with different porosities. In the validation stage the screens were inclined at 45°, 90° and 135°, (angle measured between the floor upstream and the screen plane). The validated code was used to determine the effect of screen inclination on mass flow rate through the screen and on airflow-induced forces that act on the screen. The effect of screen porosity was examined by using screens of different porosities (0.4, 0.52 and 0.62). The experimental and CFD results were in good agreement with respect to the velocity magnitude for a screen placed at 90°. Fair agreement was observed with an inclined screen that is placed at either 45° or 135°. However, at both 45° and 135° the agreement with respect to trends in air velocity vertical distribution downstream the screen was good. When the screen was placed at 90° to the floor, the air velocity downstream the screen was almost constant with height. With inclined screens the velocity increased with height for 45° and decreased with height for 135° inclination. A wider range of inclinations (30-150°) was used in the simulations to systematically study the effect of inclination on the mass flow rate through the screens and on the forces on the screens. The CFD results show that for all porosities the mass flow rate through screens that are inclined 45° was higher than through screens inclined at 135°. The higher mass flow rate at 45° was associated with larger force acting on the screen. The force acting at 45° was always greater than at 135°. © 2009 IAgrE.