Recirculating Flow and Sedimentation in the Colorado River in Grand Canyon, Arizona
Recirculating Flow and Sedimentation in the Colorado River in Grand Canyon, Arizona
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亚利桑那州大峡谷科罗拉多河的循环流和沉积
DOI：
10.1086/629435
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
J. Schmidt
中科院分区：
文献类型：
--
作者：
J. Schmidt
碎片扇进入大峡谷底部，在科罗拉多河造成急流和水流分离。流动模式和由流动分离形成的回流区的行为在整个峡谷长度内是一致的。回流区沿着通道扩张的边缘出现。回流区由一个初级涡旋组成，初级涡旋上游可能存在次级涡旋和无组织低速区。最长的回流带是由低宽深比的航道收缩形成的。回流区长度随着流量的增加而增加。砂坝形成在回流带之下，特别是在分离点和再连接点附近。再附着坝从再附着点向上游突出，并位于主旋涡的下方。分离坝覆盖着碎屑扇的下游部分，并形成在次生涡流和低速区之下。形成再附着坝的泥沙主要受悬移质的大小控制，而形成分隔坝的泥沙较细。再附着杆比分离杆更常见，两者出现的频率更高，而且在较大范围内更大。这些条的形状和位置与停滞点的位置和行为是一致的；但是，这些停滞点的位置会发生变化。虽然在大流量时，主流道内的速度有所增加，但分离点和再附着点附近的速度仍然很低。基岩峡谷可以在高流量和低输移率下发生沉积，尽管高流量沙洲的位置可能不同于低流量沙洲的沉积。
Debris fans debouching into the bottom of Grand Canyon create rapids and flow separation in the Colorado River. The patterns of flow and the behavior of recirculation zones formed by flow separation are consistent throughout the Canyon's length. Zones of recirculating flow occur along the margin of channel expansions. Recirculation zones are comprised of one primary eddy; secondary eddies and areas of unorganized low velocity may exist upstream from the primary eddy. The longest recirculation zones are formed by channel constrictions of low width-to-depth ratio. Recirculation zones increase in length with increasing discharge. Sand bars form beneath recirculation zones, especially near separation and reattachment points. Reattachment bars project upstream from the reattachment point and underlie primary eddies. Separation bars mantle the downstream parts of the debris fans and form beneath secondary eddies and low-velocity areas. Sediment that forms reattachment bars is dominated by sizes characteristic of suspended load, while sediment that forms separation bars is finer. Reattachment bars are more common than separation bars, and both occur more frequently and are larger in wide reaches. The form and location of these bars is consistent with the location and behavior of stagnation points; however, the locations of these stagnation points change. Although velocity increases in the main channel at high discharges, velocities near the separation and reattachment points remain low. Sedimentation can occur in a bedrock gorge at high discharges and low transport rates, although the location of high-discharge sand bars may differ from those deposited at lower flows.