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首页> 外文期刊>Acta Horticulturae >Aerodynamic characterisation of two large screenhouse roofs
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Aerodynamic characterisation of two large screenhouse roofs

机译：两个大型屏幕屋顶的空气动力学特征

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Large screenhouses are popular in Mediterranean horticulture, individual houses having often horizontal dimensions of over 100 m. As the size of these structures increases, the effect of ventilation through the side-walls diminishes and most of the momentum, mass and energy exchange with the atmosphere takes then place through the roof. In the limiting case of an 'infinite screenhouse', the transfer becomes one dimensional in the vertical direction. The traditional 'mixing length' analysis of vertical flux profiles over 'infinite' fields has been adapted here to flat-roof, 'infinite' screenhouses. The analysis of this configuration indicates that the aerodynamic effect of the screen is determined by just two parameters. One quantifying the horizontal shear force on the roof, and another - the effective mixing through the screen. The shear parameter can be determined from momentum flux measurements above and below the roof, and the mixing parameter can be determined from the velocity profile above the roof. Data collected in two large screenhouses, one covered with a coarse 'shade' screen and another with a fine insect-proof screen, were used to compare their aerodynamic characteristics. The shade screen absorbed 80% of the atmospheric momentum flux, while the insect-proof screen absorbed 95%. The shade screen's mixing length is estimated at 0.40 m, while that of the insect-proof screen is only 0.14 m.
机译：大型屏蔽在地中海园艺中很受欢迎，个别房屋经常卧式超过100米。随着这些结构的尺寸增加，通气通过侧壁的效果会减小，并且大部分动量，质量和能量交换随着大气层通过屋顶进行。在“无限屏幕”的限制情况下，转移在垂直方向上变为一维。传统的“混合长度”对“无限”字段的垂直通量剖面的分析已经适用于平顶，“无限”屏蔽。对该配置的分析表明屏幕的空气动力学效果仅由两个参数确定。一种量化屋顶上的水平剪切力，另一个 - 通过筛网的有效混合。剪切参数可以根据顶部和下方的动量磁通测量确定，并且可以从屋顶上方的速度轮廓确定混合参数。在两个大型屏蔽中收集的数据，一个用粗糙的“阴影”屏幕覆盖，另一个具有精细防虫屏幕，用于比较它们的空气动力学特性。阴影屏幕吸收了80％的大气动量助焊剂，而防虫屏幕吸收了95％。遮阳屏的混合长度估计为0.40米，而防虫屏幕仅为0.14米。

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