EFFECT OF NET-COVERED WINDBREAK ON LEAKAGE RATE OF A GREENHOUSE

The effect of a windbreak on the leakage rate of a greenhouse was investigated through tracer-gas measurements and a computational fluid dynamics (CFD) simulation. A net-covered windbreak with a porosity of 0.604 and a greenhouse with a floor area 6 m x 14 m were used. The windbreak had a height of 3.5 m and a length of 30 m, and it was built 7.0 m apart from the west side of the greenhouse. The windbreak reduced the wind velocities around the greenhouse to 70.9%-90.3% of those without the net of the windbreak. The leakage rate of the greenhouse with and without the net correlated significantly with the wind velocity windward of the wind break. The leakage rate of the greenhouse was reduced to 61.1% of that without the net, as evaluated using the ratio of the slopes of the regression equations. The CFD model was validated using six datasets for steady wind conditions with and without the net. The simulation results of the normalized wind velocity around the greenhouse agreed well with the measurements with and without the net. The mechanism which the windbreak reduced the leakage rate of the greenhouse was presented through a comparison of the simulated wind pressure coefficients on the greenhouse surfaces with and without the windbreak net.