INFLUENCE OF RIDGE HEIGHT OF PIPE-FRAMED GREENHOUSES ON WIND PRESSURE COEFFICIENTS.

Taller pipe-framed greenhouses (pipe houses hereafter) are required to maintain a buffer zone for an improved thermal environment or to install devices for controlling the thermal environment, such as movable curtains. This study investigates the effect of ridge height on the distributions of the wind pressure coefficient (Cp) on pipe houses based on a wind tunnel experiment using 1:20 scale models. The width and length of a standard pipe house in full scale were 6 and 50 m, respectively, while the ridge height was varied from 3.16 to 5.16 m. The results indicate that the Cp distribution on the windward roof was strongly affected by the ridge height when the wind direction was normal to the ridge line. The windward roof was generally subjected to negative wind pressure (suction). The suction had a maximum value behind the windward eave, which increased in magnitude with an increase in ridge height. This effect may be related to the flow separation at the windward eave and reattachment on the windward roof. As a result, the drag and lift coefficients (CD and CL) obtained from the Cp distribution were also affected by the ridge height. High suctions were induced locally at the ridge corner of the leeward roof with an oblique wind. [ABSTRACT FROM AUTHOR]