Effect of Suspended Anchored Spherical Energy Dissipator Blocks on Hydraulic Jump Characteristics

In an open channel, A hydraulic jump is the rapid varied flow which results water surface level increment and energy suppression. In most cases, by this phenomenon energy dissipation process is accomplished in downstream of hydraulic structures such as weirs, sluice gates and so on. The hydraulic jump is controlled by utilizing a structure called stilling basin. Building such structure can be very costly. Several approaches, such as bed roughness, chute blocks, baffle blocks and end sill, have been proposed to reduce the construction cost. For the first time, it is recommended to use the suspended anchored spherical energy dissipator blocks. From a practical point of view, this structure is very similar to baffle blocks but due to having less drag coefficient compared to the baffle blocks, they will suffer less force. Therefore, the slab thickness of basin decreases to a certain extent. Furthermore, due to fluctuations, using such dissipators leads to an increase in energy dissipation. These blocks have a relative density lower than water and are anchored by a thin resistant plastic to the floor of stilling basin. To the best of our knowledge, there are no studies on using these structures in the basin and analysis of their influences on the hydraulic jump characteristics. There are several interesting questions about the effect of such structures on the conjugate depth, jump length, and optimization of the design of the stilling basin as well. The main goal of our study is to answer these queries. In this work, 30 experiments were conducted in the range of froud numbers of 5-8 and in the form of four types of arrangement. It should be noted that, five experiments are concerned with testing the designed bed without any blocks. The Experiments were carried out in a flume with glass walls, 8 m length, 35 cm width and 40 cm heights. In order to form the hydraulic jump, the height of the walls were extended up to 80 cm in the beginning part of the flume and a chute with 30 degree angle and the height of 40 cm was set up. Next, in order to modeling such structures the obstacles diameter was set to 4 cm i.e. 1.2 times more than highest initial depth in classical hydraulic jump of present study. The size of the anchor length was chosen in such a way that the blocks do not enter into the roller environment and remain in front of impinging jet stream into the stilling basin, since no energy dissipation will occur if they enter into the roller ambient. The results showed that the arrangements decrease the jump length and conjugate depth respectively, in average to 31% and 21%. Additionally, the energy dissipation using the suspended blocks in average is around 68% that is approximately 11% greater than smooth bed. In all arrangements for experiments, conjugate depth reduction and energy dissipation increment is not impressive compared to each other, but even so the most and lowest effective arrangement respectively, was type 4 and type 3.