长江河口北槽弯道横向次生流、混合与层化

发布时间：2017-12-27 07:22

  本文关键词：长江河口北槽弯道横向次生流、混合与层化　出处：《海洋工程》2016年03期 　论文类型：期刊论文

  更多相关文章： 长江河口 北槽弯道 次生流 混合 层化 势能差异 应变

【摘要】：2013年2月25至26日(枯季/大潮)、7月23至24日(洪季/大潮)分别在长江河口北槽弯道沿着3条横向测线CS6、CSW和CS3(每条测线上有北、中、南3个站位)测得水位、流速、盐度和含沙量的时间序列资料。通过这些资料的定量计算、分析,理解弯道横向次生流、混合与层化的时、空变化和各种物理机制及其相对重要性。3条横向测线均存在横向次生流,且横向测线CS3还出现横向次生环流。枯、洪季,仅在横向测线CS6、CS3出现环状欧拉余流。枯、洪季,沿着横向测线CS3,3个站位的横向斜压梯度比离心加速度和科氏加速度都大1~2个数量级,而后两项大小接近且数量级都是10-4,罗斯贝数在1左右。这些表明:横向次生流受横向斜压梯度、离心加速度和科氏加速度共同驱动,前一项相对于后两项更加重要。沿着3条横向测线:1)枯、洪季大潮,平均势能差异分别约为54.23、66.56 J/m3,表明洪季层化强于枯季;2)枯季涨潮,平均的势能差异普遍小于落潮,而洪季涨潮,平均的势能差异普遍大于落潮,表明枯、洪季湍流混合均存在潮汐不对称性;3)枯季,由横向、纵向水深平均应变(ΦS-y、ΦS-x)引起的势能差异变化率的范围分别是-67×10~(-3)~37×10~(-3)、-7×10~(-3)~11×10~(-3)W/m~3,而洪季,相应的范围分别是-45×10~(-3)~30×10~(-3)、-14×10~(-3)~13×10~(-3)W/m~3,表明枯、洪季差异不明显,横向水深平均应变(ΦS-y)均大于纵向水深平均应变(ΦS-x),前项对水体混合与层化的影响更大;4)枯季大潮,纵向平流(ΦA-x)、横向平流(ΦA-y)、纵向水深平均应变(ΦS-x)和横向水深平均应变(ΦS-y)的潮汐平均绝对值占四项总和之比例分别为26%、33%、18%和23%,而洪季大潮,相应的值的比例分别为13%、9%、22%和56%,表明枯季,平流项(ΦA-y最大)对混合与层化的控制可能占主导地位;洪季,应变项(ΦS-y最大)可能占主导地位。无量纲数(m)被用于判别横向平流(ΦA-y)、横向水深-平均应变(ΦS-y)的相对重要性。一个概念性模式被用于显示层化与横向次生流/环流的相互关系。
[Abstract]:From 25 to 26 February 2013 (dry season / spring tide) and 23 to 24 days in July (flood season / spring tide), the time series data of water level, velocity, salinity and sediment concentration were measured along the North Bend of the Yangtze River Estuary along the 3 horizontal lines CS6, CSW and CS3 (each station has 3 stations in North, middle and South). Through the quantitative calculation and analysis of these data, we can understand the temporal and spatial variation of the lateral stream, mixing and stratification, and the various physical mechanisms and their relative importance. The transverse secondary current exists in all 3 transverse lines, and the transverse secondary circulation is also appeared in the lateral line CS3. In the dry and flood season, the annular Eulerian residual current appeared only on the horizontal line CS6 and CS3. In the dry season and the flood season, the lateral baroclinic gradient along the transverse line CS3,3 stations is 1~2 orders of magnitude larger than the centrifugal acceleration and Coriolis acceleration. The latter two items are close to the magnitude and the order of magnitude is 10-4, and Ross Bbe Gh is around 1. These results show that the transverse secondary flow is driven by the transverse baroclinic gradient, the centrifugal acceleration and the Coriolis acceleration, and the first one is more important than the latter two. 娌跨潃3鏉℃í鍚戞祴绾，

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