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

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