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首页> 外文学位 >CHARACTERISTICS OF AIR FLOW WITHIN AND ABOVE GRAIN SORGHUM CANOPIES (AIR FLOW, MEASUREMENTS, ABOVE-CANOPY, WITHIN CANOPY, WIND SPEED).
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CHARACTERISTICS OF AIR FLOW WITHIN AND ABOVE GRAIN SORGHUM CANOPIES (AIR FLOW, MEASUREMENTS, ABOVE-CANOPY, WITHIN CANOPY, WIND SPEED).

机译：谷物高粱冠层内部和上方的气流特征（气流，测量，冠层上方，冠层内部，风速）。

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摘要

Wind speeds were measured within and above grain sorghum canopies planted in north-south oriented rows at Mead, Nebraska in 1982 and 1983. In both years, a 0.76m row spacing was used in the main field. The plant population ha('-1) was about 276,000 in 1982 and 118,500 in 1983. A secondary field was used in 1983 with double row spacing and 95,000 plants ha('-1). Data were analyzed for periods when wind direction (measured at 3m) ranged from southeast to southwest.;Wind speeds decreased monotonically with depth in the upper and middle portions of the canopies. Reversal in wind speed gradient and presence of a secondary wind speed maximum was observed in the lower portion of the canopy. This secondary maximum was quite pronounced in the wide-row canopy under windy conditions. The penetration of flow into the canopies was increased with change from stable to unstable conditions.;Several models of within-canopy air flow were evaluated against the observations made in this study. Only in the upper portion of the denser canopy did the empirical models (Inoue, 1963; Cionco, 1965; Cowan, 1968; Landsberg and James, 1971; Thom, 1971) predict wind speeds reasonably well. The second order closure model (Wilson and Shaw, 1977) predicted wind speeds midway between two rows within the denser canopy fairly well. The secondary maximum observed in the lower portion of the canopy was accurately predicted by the model. The prediction capability of both empirical and second order closure models was poor for the sparser canopy (1983).;The roughness parameter (z(,o)) and zero-plane displacement (d) increased with increasing crop height (h). Information on z(,o)/h and d/h was developed for various stages of crop growth. Mean values of z(,o)/h and d/h for full crop development (under moderate wind speed) were 0.096 and 0.61 in 1982. Corresponding values in 1983 were 0.074 and 0.54. In both years, z(,o)/h and d/h decreased with increasing wind speed. Mean values of the crop drag coefficient (C(,d)) for the fully developed canopies under moderate wind speed were 0.055 in 1982 and 0.035 in 1983.
机译：分别于1982年和1983年在内布拉斯加州米德（Mead）以南北定向的行种植的高粱谷冠内和上方测量了风速。在这两年中，主田使用0.76m的行距。 1982年的植物种群ha（'-1）大约为276,000，1983年的植物种群为118,500。1983年使用了一个具有双行间距和95,000株ha（'-1）的次田。分析了风向（在3m处测得）从东南向西南变化的时期的数据；风速随冠层上部和中部深度的增加而单调降低。在冠层的下部观察到风速梯度的逆转和次级风速最大值的存在。在有风的条件下，该第二最大值在宽行雨棚中非常明显。从稳定状态到不稳定状态的变化，增加了对冠层的渗透率。根据本研究的观察结果，评估了几种冠层内部空气流模型。经验模型仅在较密的树冠上部（Inoue，1963; Cionco，1965; Cowan，1968; Landsberg and James，1971; Thom，1971）才能很好地预测风速。二阶封闭模型（Wilson和Shaw，1977）对较密集的树冠内两行中间的风速进行了很好的预测。该模型准确预测了在冠层下部观察到的次要最大值。稀疏冠层（1983）的经验模型和二阶闭合模型的预测能力均较差。粗糙度参数（z（，o））和零平面位移（d）随着作物高度（h）的增加而增加。有关z（，o）/ h和d / h的信息是针对作物生长的各个阶段开发的。整个作物生长（在中等风速下）的z（，o）/ h和d / h的平均值在1982年为0.096和0.61。1983年的平均值为0.074和0.54。在这两年中，z（，o）/ h和d / h随风速增加而降低。中等风速下完全发达的冠层的作物阻力系数（C（，d））的平均值在1982年为0.055，在1983年为0.035。

著录项

  • 作者

    AZEVEDO, PEDRO VIEIRA.;

  • 作者单位

    The University of Nebraska - Lincoln.;

  • 授予单位 The University of Nebraska - Lincoln.;
  • 学科 Engineering Agricultural.
  • 学位 Ph.D.
  • 年度 1984
  • 页码 157 p.
  • 总页数 157
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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