河口航道双丁坝影响下异重流运动特性

Effects of Double Groins on Motion Characteristics of Density Current in Estuarine Navigation Channel

摘要:

在河口地区，由密度梯度驱动而产生的异重流是影响航道内泥沙输移的重要因素之一。作为航道整治中常见的建筑物，丁坝群可以缓解航道的泥沙淤积问题、提高通航能力。为探究双丁坝对异重流运动特性的影响，运用粒子图像测速系统（PIV）开展了开闸式异重流实验，研究了在不同束窄系数情况下，航道异重流稳定阶段内的流场及湍流特性，并对比分析了异重流在两个丁坝位置特征断面处的单宽流量及总流量。结果表明，双丁坝改变了航道内的流场，异重流在经过束窄断面后会向第二个丁坝后部区域横向扩散，进而使得流速加大、高度降低；异重流在两个丁坝束窄断面的单宽流量近似相同，且与束窄系数无关；异重流在束窄断面的总流量与断面宽度成正比，在实际工程中可以通过适当调整丁坝长度来控制侵入航道的异重流总量。

关键词:异重流;双丁坝;粒子图像测速;流速场;湍流特性;流量

Abstract:

In estuaries， the density current driven by the density gradient is one of the most important factors affecting sediment transport in the channel. As the common buildings in the channel regulation， the groin group can alleviate the siltation and improve the navigation capacity. In order to explore the influence of double groins on the motion characteristics of density current， the particle image velocimetry （PIV） was used to measure the flow fields and turbulence characteristics of the lock-exchange density current in the stable stage under different narrowing coefficients. The unit flowrate and total flowrate of the density current at the two groin sections were compared. The results show that the double groins change the flow field in the channel. After passing through the narrowed sections， the density current diffuses laterally to the rear area of the second groin， resulting in the increase of velocity and the decrease of height. The unit flowrate of the density current in both sections of the two groins is approximately the same， which is independent of the narrowing coefficient. The total flowrate of the density current in the narrowed section is proportional to the width of this section. In practical engineering， the appropriate lengths of the groins can control the total amount of density current intruding channel.

Key words:density current;double groins;particle image velocimetry;velocity fields;turbulence characteristics;flowrate