| The distribution of air speed and the influence factors of it in the sunlight greenhouse were studied in this essay and a discussion on the importance of wind speed factor to the greenhouse'performance is conducted for developing improved designs with respect to ventilation efficiency. Based on the experiment, a systematic analysis of the air speed in the energy-saving sunlight greenhouse was performed with the use of computational fluid dynamics (CFD). Firstly, the validity of the model assumptions was established by comparing the numerical results with experimental data. A further study was conducted in support of the former research to find the relationship between growth and development of muskmelon and the air speed, thus determine the optimal air speed for muskmelon planted in sunlight greenhouse according to the shape and physiological index. Following conclusions were obtained based on the research:1. The research on the effects of the outdoor wind speed and the ventilated area on the indoor air speed and the distribution regularity of the wind speed in the sunlight greenhouse showed that the changing regularity of air speed demonstrated double apex curve in the fine and demonstrated sigle apex curve in the cloudy sky, which is influenced by two major aspects. The distribution regularity of air current speed in the sunlight greenhouse is: the fluctuation from the east to west direction is not obvious while the north to south direction assumes"V"shap distribution, which is determined by the distance from the vent that is the air speed increases as the distance decreases, the opposite is true.2. In the greenhouse, the wind speed-discounting rate increased as the height went up. As we found the optimal ventilation area ratio is between 18% and 25%. There exist a strong linear relationship between the indoor air current velocity and the outdoor wind speed when ventilation area ratio is 25.2%. In the energy-saving sunlight greenhouse, the air speed changes positively as the outdoor wing speed.3. The discrepancy of the indoor temperature witnessed a rapid drop at first and then decreased gradually when the ventilation area ratio increase from 12.7% to 25.2%, meanwhile the average temperature discrepancy between the indoor and outdoor dropped from 2.36℃to 1.34℃. Particularly, the discrepancy of the indoor temperature drops slowly when ventilation area ratio ranges from 18.8% to 25.2%. It indicates that when the ventilation area ratio stayed around 18%25%, the best efficiency of ventilation can be secured.4. The systematic analysis of the strength of illumination, air temperature, the indoor air speed, soil temperature and relative humidity of the air suggested that number of the principal factor is 4, which accounts for 96.77% of the total information content. Further variance enormous revolving analysis illustrated that the first principle factor was determined by X(2) (air temperature) and X(4) (soil temperature), the second ,third and forth principle factors were mainly decided by X(1) (strength of illumination),X(3)(indoor air speed) and X(5) (air relative humidity) respectively. It has proved that air speed is on of the major factors that affect the microenvironment inside the green house.5. A systematic analysis of the distribution of air speed in the sunlight greenhouses under natural ventilation process was performed with the use of computational fluid dynamics (CFD). And a predication of the distribution of the inside flow field was performed. A good agreement between the numerical data and the experimental measurements was found if a standard k-εturbulence model is applied in the CFD simulation, which proved the feasibility to select the CFD software to conduct the study on the natural ventilated sunlight greenhouse. Under the similar condition, the average air speed inside the greenhouse obtained from the CFD simulation is -0.00239m/s lower than that from the experimental measurement when the ventilate the area ratio is12.7%, and it is 0.079441m/s higher when the ventilate the area ratio is 25.2%. The average variances of the result are 1.258494% and 18.29776% of the experimental results.6. The distributional information secured through CFD simulation of the experimental sunlight greenhouse illustrated that the air current velocity is bigger around the three vents and that of the top vent is the biggest. The air speed reduced dramatically from the vents to the interior of the greenhouse like a sphere. The lower middle of the greenhouse forms a comparatively high speed zone with no fierce change and the top area is a low speed space with the air speed decreased as the height increased. The establishment and location of the vent on the back wall indicated no obvious affect on the improvement of ventilation efficiency and it formed two obvious low speed turbulent on the two sides of the vent.7. The effect of different air speed (0.0 m·s-1 (CK),0.4 m·s-1 (A-1),1.0 m·s-1 (A-2),2.2 m·s-1 (A-3)) on the growth and development of muskmelon during fruitage in the greenhouse was analyzed. The results showed that the optimal air speed was treatment A-2. Comparing with CK, 21.68% more leaf area, 63.06% more LAI, 120.32% higher Gs, 2 days earlier maturation, 24.43% more yield, 11.07% higher total sugar were obtained in this treatment. Likewise, we found that TSS and protein increase with the air speed; Compared with CK, A-3 is 13.88% more in the item of TSS, 3.6% more in the content of protein whereas the reduce sugar content decrease with the air speed, CK is 10.53% more than A-3. There exist no significant difference in the items of pulp of melon and vitamin C. It proved that the effect of different air speed in greenhouse on muskmelon was significant and the optimal air speed is 1.0 m·s-1.
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