| 摘要: |
| 大尺度散粒体是山区河流常见的床面粗糙元素。为探讨大尺度散粒体形态对周围水流结构的影响规律，采用高度均为Δ的正方体、球体和四面体3种散粒体进行单体水槽试验，基于声学多普勒流速仪获得的瞬时流速资料，开展大尺度散粒体周围水流结构研究。结果表明：（1）水深h较小，h/Δ=0.9，散粒体处于非淹没状态时，其周围水流呈U形向下游扩散，正方体的横流区范围最大，球体次之，四面体最小；水深增大，h/Δ=1.8，散粒体处于淹没状态时，其周围横流将明显减弱，水流越过散粒体后在下游形成波状起伏。（2）表层合流速Um/U随弗劳德数Fr和散粒体阻水面积的增大而增大，Fr较大时，高速区主要出现在散粒体平面形心附近，最大值可达试验流速的1.3倍，正方体、球体和四面体对应的表层Um/U平面分布分别呈等腰梯形、钟形和菱形；强横流区位于散粒体形心两侧1.5Δ范围内，最大横流可达试验流速的19%。（3）Fr较小时，散粒体对纵向流速u/U垂线分布的影响较小，上游断面u/U与指数分布规律吻合，下游Δ处u/U垂线分布变化明显，此后u/U垂线分布逐渐恢复为指数分布；Fr增大后，散粒体对u/U垂线分布影响的差异逐渐增强，u/U垂线分布不再服从指数分布。 |
| 关键词: 大尺度散粒体 明渠紊流 水面形态 流速分布 |
| DOI： |
| 分类号:TV131.2 |
| 基金项目:国家自然科学基金资助项目(51509026)；重庆市基础科学与前沿技术研究项目（cstc2017jcyjAX0278） |
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| Flow structures around large-scale artificial roughness elements |
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ZHONG Liang1,2, JIANG Tong2, HAN Zhengguo3
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1.National Engineering Research Center for Inland Waterway Regulation, Chongqing Jiaotong University, Chongqing;2.Key Laboratory of Hydraulic and Waterway Engineering of the Ministry of Education, Chongqing Jiaotong University, Chongqing;3.Zhejiang Yurui Engineering Consulting Co., Ltd., Hangzhou
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| Abstract: |
| Large-scale artificial roughness (LSAR) is a common element of bed roughness in mountain rivers. To investigate the influence of LSAR morphology on surrounding flow structures, three LSAR shapes (cube, sphere, and tetrahedron) with the same height (Δ) were used in a single flume experiment. Instantaneous flow velocity data were acquired using an Acoustic Doppler Velocimeter. The results show that: (1) When the water depth is small (h/Δ=0.9) and the LSAR is in a non-submerged state, the three LSAR shapes are surrounded by a downward Ushaped flow. The transverse flow area around the cube is the largest, the second largest is around the sphere, and the smallest around the tetrahedron. When the water depth increases (h/Δ=1.8) and the LSAR is in a submerged state, the transverse flow around it clearly weakens, and water flows over the LSAR and forms undulating downstream waves. (2) The resulting surface velocity Um/U increases as the Froude number (Fr) and the water hindrance area increases. When Fr is large, a high velocity zone in the surface layer appears near the plane centroid of the LSAR, and the maximum velocity in this zone can be up to 1.3 times the test velocity. The distribution shape of Um/U in the surface layer around the cube, sphere, and tetrahedron is that of an isosceles trapezium, bell-shaped, and rhombus, respectively. The high transverse velocity zone is in the 1.5Δ range on both sides of the plane centroid of the LSAR. The maximum value can be up to 0.19 times the test velocity. (3) When Fr is small, the LSAR has little influence on the vertical distribution of longitudinal velocity u/U. In the upstream section, u/U essentially follows a exponential distribution, and the distribution clearly changes at 1Δdownstream of the LSAR. Subsequently, the vertical distribution of u/U gradually returns to an exponential distribution. As Fr increases, the influence of LSAR on the vertical distribution of u/U gradually increases, and the distribution of u/U is no longer exponential. |
| Key words: Large-scale artificial roughness open-channel turbulence water surface morphology velocity distribution |
