Wind effect and optimization of multi-span greenhouses with different roof

• Influence of greenhouse roofs on the ventilation and wind-resistance are compared. • Collaborative optimization method on the multi-span greenhouse roof are proposed. • The sawtooth multi-span greenhouse with a protective span is better. Multi-span greenhouses are popular for rain-protected and summer cultivation, but they face challenges in cooling and wind-resistance. This study develops a three-dimensional unsteady wind-temperature coupling model to optimize greenhouse roof structures. Effects of the three roof geometries, namely arched greenhouse (ARC), standard sawtooth greenhouse (SAW), and sawtooth greenhouse with a protected span (SAWs), on the collaborative performance of greenhouse ventilation and wind-resistance were systematically revealed. Results revealed that the SAW roof enhanced airflow through a vertical vent deflector, significantly boosting ventilation efficiency (from 2.60 to 4.91 in the unsteady period) and improving wind and temperature conditions (0.35 to 0.49 m/s wind speed and 0.46 °C temperature reduction in the steady period) compared to the ARC design. However, the abrupt geometry changes increased localized wind pressure coefficients. The innovative SAWs roof design with a reverse protection span effectively mitigated performance trade-offs, reducing the maximum wind pressure coefficient from 3.61 to 1.60 while maintaining high ventilation efficiency (4.04) and balanced wind pressure distribution across different wind directions. Overall, the SAWs greenhouse has the advantages of wind safety, ventilation and cooling, providing a theoretical basis and design paradigm for collaborative optimization of the greenhouses.