Evaluation of structural characteristics of naturally ventilated multi-span greenhouses using computer simulation

Natural ventilation system modifications were evaluated using a computation al fluid dynamics (CFD) numerical model (code: Fluent version 4.5). Wind sp eed and direction, side vent opening size and location, roof vent opening t ype, and number of spans were examined in terms of ventilation rates and ai rflow distribution. For the side vent located at 2.5 m above the floor with a west wind of 2.5 m/s, 59 % of the incoming air through the side vent was predicted to move out through the first roof vent opening without leaching distant areas in the greenhouse, resulting in high inside air temperatures . The air mainly moved in through the side vent and fourth roof vent openin gs for an east wind of 0.5 m/s while the third and fourth roof openings wer e the only predicted inlets of airflow for an east wind of 2.5 m/s. The hin ged open roof multi-span greenhouses were predicted to have significantly h igher natural ventilation rates than the double polyethylene-covered multi- span greenhouses for all the spans in the absence or side vent.