Air flow, temperature and humidity patterns in a greenhouse tunnel

Air distribution and climatic heterogeneity in greenhouses interfere with plants activity and influence largely crop activity and more particularly transpiration and photosynthesis. This is particularly true for the tunnel, which is likely the most frequently used greenhouse type in the Mediterranean basin, but which generates also a high climatic heterogeneity. Up to this time, most experimental studies of ventilation on full-scale greenhouses have used tracer gas techniques that allow neither clear identification of the component of the total flux, nor predictions of the air flow pattern. This lack of experimental data and the complexity of the turbulent flows around intricate boundary conditions explain why detailed air motion inside greenhouse remain poorly known and seldom considered in greenhouse numerical simulation. It is the reason why we characterised the mean air flows together with air temperature and humidity patterns in a classical 8 m width "Filclair" tunnel situated in the region of Avignon in the south of France. Using three- dimensional sonic anemometers and krypton hygrometers, the mean air speed, temperature and humidity were investigated in two vertical cross sections of a tunnel. The spatial distribution of air flow is presented, together with the associated temperature and humidity patterns. These results reveal a strong climatic heterogeneity in the tunnel.