عنوان مقاله [English]
The design of stilling basin always corresponds to the fact that the length of the jump should be restricted to the length of stilling basin. Baffle blocks are hydraulic structures, installed in the basin in order to stabilize the jump and reduce the length of the jump. Flow under the condition of submerged hydraulic jumps with baffle blocks could be observed as two regimes: The deflected surface jet (DSJ) and reattaching wall jet (RWJ). The formation of each regime relates to different factors, such as block shape and location, submergence factor, block size, and Froude number of entrance flow.In this article, a numerical study was conducted to investigate the influence of some parameters, including blocks height and shape, the distance of blocks from a gate and the distance between the blocks, on the length of submerged hydraulic jump with baffle blocks. The FLUENT software has been used for 3D RANS simulation. Twenty models with different geometrical conditions according to the mentioned parameters were created.
It was observed that for DSJ regime, the length of the submerged hydraulic jump is reduced more than 40% based on the distance of baffle blocks from sluice gate. It means that, it can be expected to see more reduction in length of the jump as the blocks are installed closer to the gate. However, for RWJ regime, the decrease of the length is limited to less than 14%. So, due to this considerable difference between the operations of these two regimes, the noticeable point is that all the conditions should be in the way so that the flow occurs as a DSJ regime. In addition, it can be concluded from the results that increasing the height of blocks more than the thickness of entrance jet cannot make any effective change in the length of the jump. Furthermore, it was observed that using baffle wall (i.e., a continual wall which spreads along the whole width of a channel), instead of baffle blocks in the same condition, increases the length of the submerged hydraulic jump. The reason is that the vortices that are formed due to submerged jump's conditions become more intense as the baffle wall deflects the whole jet into the surface. Thus, in this situation vortices have more impact on the flow.