Author(s): Sui Liang Huang; Chiu-On Ng
Linked Author(s): Suiliang Huang
Keywords: Navigational channel; Submerged weir; CCHE3D; Numerical modeling
Abstract: In the second part of this work, the effect of a single submerged weir of different sizes with different approaching flow conditions on the flow in the physical model channel is numerically investigated using the CCHE3D hydrodynamic model. The applicability of a single weir in the channel is evaluated based on the difference in transverse velocities and flow deviation angles with and without the weir. The secondary flows for differently sized submerged weirs and the flow conditions in the channel are quite similar, and all of the flows break up upstream of the weir and then develop, decay, and recover downstream of the weir, except in the case of a long weir with 0 degrees. For such a long weir, the single secondary flow still breaks up upstream in the vicinity of the weir, but no obvious development of three secondary flow zones downstream of the weir is numerically observed. This strongly implies that the flow in the river bend with a submerged weir results from the interaction between the channel shape (gravity) and the weir, and that the influence of the weir significantly depends on its size. There are two effects of the weir on navigational conditions. Generally speaking, the effect of the weir far upstream and far downstream on navigational conditions can be ignored. In the vicinity of the weir upstream (where the breaking up of the secondary flow occurs) and along the inner bank downstream of the weir, the transverse velocities and flow deviation angles increase compared with the situation without the weir, and the navigational conditions worsen. The main improvement in navigational conditions as a result of the weir generally occurs at the center of the channel and near the outer bank downstream of the weir, which are more important zones for navigation and are where the secondary flows develop, decay, and recover. To obtain a greater improvement in navigational conditions, a long weir with a large angle is generally recommended.
Year: 2007