Optimisation of Greenhouse Insect Screening with Computational Fluid Dynamics

The effect on airflow and climate of greenhouse insect screening of a 1000 m2 multi-span rose greenhouse was numerically investigated by means of a computational fluid dynamics (CFD) model, which included the dynamics, thermal and water vapour transfer between the crop cover and the greenhouse air. The numerical results were at first validated against air exchange rate data using a tracer gas (N2O) technique collected in an experimental greenhouse. Using CFD facilities, these measurements were compared with simulated decay data issued from the numerical model of the greenhouse. Good agreement was found between experimental and numerical results for different wind speeds and directions. In a second stage, this numerical model was used to investigate the effects of greenhouse insect screening (anti-Bemisia) on natural ventilation and inside climate. The consequences of windward and leeward openings were studied together with the use of two insect screen types (anti-Thrips and anti-Bemisia). The main results are then discussed with respect to crop protection and climate control procedures, and it is shown that temperature and humidity rise due to insect screening can be balanced by simple arrangements of the system, such as wiser orientations of the roof vents and the use of additional side openings.