Wind pressure coefficient of a pipe-framed greenhouse and influence of the side gable openings using a wind tunnel

Abstract

The wind pressure coefficients Cp on a pipe-framed greenhouse(or simply ‘pipe house’), whose shape consists of two or more curvatures, have been evaluated with a 1:20 scale model in a turbulent boundary layer. The length/width ratio of the model was 8.3. The Cp distribution was evaluated at various cross-sections of the model for various wind directions θ from 0°(normal to the ridge) to 90°(parallel to the ridge). The evaluated Cp distribution for θ=0°was compared with the specifications for greenhouses with gable and circular arc roofs in the current design standard for greenhouse structures, and a significant difference was observed. The Cp distribution changed significantly with wind direction. The largest negative Cp value was about -3.5 near the ridge corner when 8=25°. The influence of side gable openings on the external pressure coefficient Cpe and internal pressure coefficient Cpi were also investigated. It is found that the Cpe distribution was not affected by the openings. On the other hand, the influence of openings on the Cpi value was significant. When 8=0°, the value of Cpi was as low as -0.9, which sifted the net wind force coefficient Cf to a positive value. The value of Cpi depended on the location of the openings as well as on the wind direction. When θ= 90°, the value of Cpi varied from -0.2 in the leeward opening case to +0.5 in the windward opening case.