Knowledge Resource Center for Ecological Environment in Arid Area
| 不同外形粗糙元覆盖沙床面防风蚀效益的风洞模拟实验 | |
| 其他题名 | The Wind tunnel experiment of Anti-erosion efficience on the sand beds coverd by different shapes of roughness-elementes |
| 樊瑞静 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 李生宇 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 在塔克拉玛干沙漠腹地，发现存在有沙粒胶结体，前人实验证明，沙粒胶结体具有与砾石类似的防风蚀效益,且胶结体外形及其不规则。为了探究覆盖沙面的粗糙元的几何外形对其防风蚀效果的影响，本实验选取了：球形，三棱锥形，圆柱形，正方体形，饼形和半球形6种形状的粗糙元，（实验所用粗糙元模型自制，并保持单个颗粒的质量相等），用盖度为10%的粗糙元覆盖流沙面，分别在无沙源供给的净风和有沙源供给的挟沙风条件下，进行风洞模拟实验。实验结果表明：（1）无沙源供给的净风时，饼形粗糙元、半球形粗糙元覆盖床面的风蚀量最大，且明显高于球形粗糙元、三棱锥形粗糙元、圆柱形粗糙元和正方体形粗糙元覆盖床面。饼形粗糙元、半球形粗糙元的抗风蚀作用也差于其他四者。风沙流结构值也表现出一定的差异，1cm高度范围内（粗糙元高度范围内），输沙量由大到小依次为：CK＞饼形、半球形粗糙元＞球形、圆柱形、三棱椎形、正方体形粗糙元。风速＜10m/s时，0~3cm含90%的输沙，风速＞10m/s时，在0~5cm以内含90%的输沙。随着风速的增大，风沙流结构特征值λ随风速的增大而逐渐增大，表示床面随着风速的增加呈易被风蚀状态。（2）有沙源供给的挟沙风条件下，床面的蚀积状态随着风速的增加有着不同的变化，其中球形、三棱柱形、圆柱形粗糙元覆盖的沙面由风积向风蚀转化，且风蚀量随风速的增加而增大。当风速＞10m/s时，床面出现强烈侵蚀的现象，实验表明饼形粗糙元、半球形粗糙元的阻沙功差于其他四者，其覆盖沙面的风蚀率也最大。1cm（粗糙元平均高度）高度范围以内，输沙率由大到小依次为：CK＞饼形、半球形粗糙元＞球形、圆柱形粗糙元、正方体形和三棱锥形粗糙元。各个风速条件下，0~7cm高度含有90%的输沙。风沙流结构特征值表示，当风速为8m/s时，6种外形粗糙元覆盖沙面接近蚀积平衡的状况，随着风速的增大，床面逐渐呈现为易吹蚀的状态。（3）各个外形粗糙元床面的风速廓线也有一定的区别。1cm(粗糙元平均高度)处，风速随着粗糙元方向比率的增大呈减小趋势。对方向比率相同的的球形和正方体形粗糙元来说，正方体形粗糙元的阻风作用略优于球形。大于床面高度7cm处，床面风速基本处于稳定状态。（4）无论有无沙源供给的风速时，床面风蚀状况均易受到风速、粗糙元的外形（方向比率AR、粗糙元的高度h）和间距等因素的影响，在相同的覆盖度条件下，细高、边界明显（三棱椎形、圆柱形）的粗糙元对其覆盖床面的防护效益好于粗矮（饼形）的粗糙元。 |
| 英文摘要 | In the hinterland of the Taklimakan Desert, it was found that there were Gravel-size Sand Cemented Bodies(SCB), and that the SCB had similar wind erosion benefits to the gravel-stone. The shapes of Gravel-size Sand Cemented Bodies were irregular. In order to study the inhibitory effect of the geometric shape of the sand surface roughness covering on the surface sand movement, this paper uses the spherical, triangular pyramid, cylindrical, square, pie and hemispherical six kinds of roughness（keep the single grain quality is equal), and choosethe coverage is 10% on the sand surface which is a emprical value that the influence each other is weak. Respectively, in the non-sand wind and sand wind conditions were carried out wind tunnel simulation experiments. Experimental results show:(1) Under the non-sand wind conditions,The wind erosion of the spherical, triangular pyramid, cylindrical and square roughness covering the bed surface is obviously smaller than that of the cake and hemispherical cover, square, and the anti-erosion efficiency of cylindrical, triangular and spherical is also better than pie and hemisphere. In the range of 1cm height (roughness height), the sediment transport capacity is in the order of CK> cake, hemispherical> spherical, cylindrical, triangular, square shapes. When the wind speed<10m 0="" the="" 3cm="" height="" capcity="" of="" sediment="" transport="" when="" wind="" speed="">10m/s, 0 ~ 5cm height capcity 90% of the sediment transport sand. With the increase of wind speed, the characteristic value of sand flow structure is easy to be eroded.(2) Under the conditions of sandstorm, the spherical, triangular prismatic and cylindrical covered sand surface is transformed from wind erosion to wind erosion with the increase of wind speed. The wind erosion increases with the increase of wind speed. When the wind speed is more than 10m/s, the sand bed surface showed a strong erosion, which cake shape and hemispherical ‘s sand barrier function is weak, which the wind erosion rate of the largest. On the 1cm height range, the sediment transport rate from large to small in order: CK> pie, hemispherical> spherical, cylindrical, square and triangular pyramid. Under each wind speed, 0 ~ 7cm height contains 90% of the sediment transport. When the wind speed is 8m / s, the surface roughness covering the bed surface exhibits an eutectic equilibrium state. With the increase of the wind speed, the bed surface is easy to be eroded.(3) There are also differences in the wind profiles of the bed with the different shpes element roughness. Within the height of the roughness, the wind speed decreases as the ratio of the roughness direction increases. In the case of spherical and square shapes with the same directional ratio, the chimeric effect of the square-shaped roughness is better than that of the spherical shape. When the height is greater than 7cm, the wind profiles is tend to be stable.(4) Whether it is non-sand wind, or sand wind conditions, the wind erosion are affected by the roughness’s direction of the ratio, height and spacing and other factors, on the conditions of the same coverage, fine high, with a clear boundary roughness’s protection benefits better than lower round roughness. |
| 中文关键词 | 粗糙元 ; 几何外形 ; 风蚀率 ; 风洞实验 |
| 英文关键词 | Geometric shape Roughness elements Wind erosion Wind tunnel experiment |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 环境工程 |
| 来源机构 | 中国科学院新疆生态与地理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288015 |
| 推荐引用方式 GB/T 7714 | 樊瑞静. 不同外形粗糙元覆盖沙床面防风蚀效益的风洞模拟实验[D]. 中国科学院大学,2017. |
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