FLOW PATTERNS DOWNSTREAM SCREENS OF DIFFERENT POROSITIES

The use of screens to reduce insect entry into greenhouses has become a common practice in many countries.
The exclusion of very small insects such as thrips requires the use of fine mesh screens which impede ventilation and thus may increase air temperature and humidity within the enclosures (greenhouses or screenhouses). CFD simulations were done to explore ways in which the resistance of screens to airflow can be reduced by altering screen inclination relative to the prevailing wind.
Three inclination angles were tested: 45, 90 and 135°, where zero degree angle points towards the upstream mean wind direction.
Screens with different porosities (0.4, 0.52 and 0.62) were examined in each angle of inclination.
The CFD simulations were done with the ANSYS-CFX software package.
Flow patterns downstream screens with the lowest and highest porosities (0.4 and 0.62) are presented and discussed.
The simulation results show that the mass flow rates were higher through screens that are inclined 45° than through screens that are inclined 135°. The mass flow rates were higher by 28, 12 and 6% with the 0.4, 0.52 and 0.62 porosities respectively.

International Symposium on High Technology for Greenhouse Systems: GreenSys2009

M. Teitel, D. Dvorkin, J. Tanny

CFD, greenhouse, resistance, ventilation

https://doi.org/10.17660/ActaHortic.2011.893.61