Research on the optimization of agricultural greenhouse aerodynamic shape considering the characteristics of flow field distribution

The aerodynamic profile is a paramount factor governing the wind resistance performance of agricultural greenhouse structures. To optimize these profiles, this research conducted a systematic investigation into three representative cross-sectional types: arched, M-shaped, and gable-roof greenhouses. A robust, multi-method approach was employed in the study. Initially, Particle image velocity (PIV) experiments were performed to acquire detailed data on the external flow fields around scale models, revealing distinct spatial distribution characteristics and key differences among the three shapes. Subsequently, Large eddy simulation (LES) technology was utilized to conduct an in-depth analysis of the instantaneous distributions of both fluctuating vorticity and surface wind pressure coefficients in the external flow fields. By integrating empirical results from PIV with high-fidelity numerical data from LES, a comprehensive comparative analysis was performed on the surface wind pressure coefficients, overall wind loads, and fundamental flow mechanisms associated with each cross-section. Finally, leveraging the specific flow separation characteristics identified for the gable-roof type, a parametric method was applied to optimize its aerodynamic shape. The findings revealed several critical insights. Regardless of the roof shape, a pronounced vorticity peak was consistently observed near the roof region, with the magnitude of this peak slightly lower for the gable-roof greenhouse than for the arched and M-shaped types. In the wake region, both the M-shaped and gable-roof greenhouses exhibited a smaller zone of negative (reverse) flow velocity compared to the arched design. However, their sharp geometric edges induced more abrupt flow separation, leading to the generation of stronger vertical velocity components. A significant distinction was noted in the near-surface flow topology: while extensive attached vortex systems were present on the windward sides of the arched and M-shaped roofs, the gable-roof profile demonstrated markedly cleaner flow attachment with minimal attached vortices. This fundamental difference in flow interaction directly resulted in substantial variances in aerodynamic forces. The lift force on the gable-roof greenhouse was calculated to be approximately 49% and 28% lower than that on the arched and M-shaped greenhouses, respectively, endowing it with superior inherent resistance to wind uplift—a critical performance metric under strong wind conditions. The parametric shape optimization, involving a downstream shift of the ridge line for the gable-roof type, yielded further performance improvements. Under a 0° wind direction, this modification attenuated surface vortices. The wind pressure on the windward surface transitioned from positive to negative with a decreasing magnitude, and its contour distribution became more dispersed. Concurrently, the leeward suction pressure also decreased, exhibiting a more gradual spatial gradient. Consequently, the overall wind load on the structure was significantly reduced. Specifically, in the optimized configuration (Case P8) compared to the baseline with the most forward ridge (Case P1), the total lift and drag forces on the greenhouse surface decreased by 29% and 45%, respectively—demonstrating a clear enhancement in the wind resistance performance of the optimized structure. In conclusion, this integrated experimental and numerical study elucidates the profound influence of cross-sectional geometry on the complex flow-structure interaction and the resulting wind loads on agricultural greenhouses. The results, particularly the quantified performance benefits of the optimized gable-roof design, provide valuable, physics-based guidance for the wind-resistant design of such structures, contributing to their safety and durability in wind-prone environments.