Specifying wind speeds causing damage to screen-house crops and quantifying effects on tidal damage

Screen-houses used for growing crops on the islands of southwestern Japan can mitigate damage such as greenhouse collapse caused by strong winds. Wind loads on greenhouses with screens are lower than those with plastic film because the screens are porous. The lower loads lead to reduced risks of greenhouse collapse. Nevertheless, air currents passing through a screen’s mesh have frequently caused wind damage to screen-house crops. Wind damage, as used herein, refers to damage to leaves caused by wind pressure. To use screen-houses for strong wind protection more effectively, greenhouses must be designed not only for collapse prevention, but also for crop damage mitigation. Using field tests, this study measured the air flow characteristics and wind reduction rates of screen-houses. Wind tunnel experiments elucidated the wind speeds sufficient to damage all major crops grown in screen-houses in the southwestern islands: mango, hot pepper, and okra. As a result, the critical wind speed for mangoes was found at 8 m s^-1, for hot pepper leaves was set as 4 m s^-1, for okra leaves was set as 6 m s^-1. Knowledge of screen-house wind reduction rates and wind speeds sufficient to damage crops is useful to design wind damage reduction methods for crops in screen-houses. Results confirmed that wind speed reduction reduces wind damage to mangoes, and also reduces tidal damage.