Mean and turbulent air flows and microclimatic patterns in an empty greenhouse tunnel

The turbulent air flow along with patterns of air temperature and humidity transport were studied in a classical 'Filclair' tunnel, situated near Avignon in the south of France. Measurements with three-dimensional sonic anemometers and rapid-response hygrometers revealed a strong heterogeneity in the windward side of the tunnel. For winds perpendicular to the axis of the tunnel, the air how exhibited a strong current crossing the tunnel between the windward and leeward openings and moderate air velocities in the vertical section situated between two consecutive series of openings. The temperature distribution showed a north-south gradient due to the cold air penetration through the vent opening and a vertical gradient above the soil surface due to solar energy absorption at the soil level. Air water vapour patterns were quite different from air temperature patterns, with 'humid' areas only concentrated along the soil surface close to the source of evaporating water. Analysis of the energy spectra showed that all the locations had similar spectral levels in the dissipation region. (C) 2000 Elsevier Science B.V. All rights reserved.