FLOW REDUCTION OF SYNTHETIC SCREENS OBTAINED WITH BOTH A WATER AND AIR-FLOW APPARATUS

Wind breaking cloths, ventilation screens and insect nettings reduce w ind velocity and indoor ventilation because of their flow resistance w hich causes flow reduction. Knowledge of the flow reduction is importa nt to compare materials and to predict their behaviour for specific ap plications. Flow reduction is defined as the difference in flow veloci ty with and without agrotextile, the other circumstances remaining the same. The flow reduction coefficient of an agrotextile is the flow re duction expressed as a percentage of the flow velocity without agrotex tile. Some commercial agrotextiles were tested in both a water and air flow apparatus to determine their flow reduction coefficient. Since th e flow of water and the flow of uncompressed air obey the same laws, s imilar results were obtained. Moreover, a relation was found between t he open area of the fabrics and the flow reduction coefficient. (C) 19 98 Silsoe Research Institute.