Investigating the use of submerged vanesin reducing scouring in downstream of stilling basin (Case study: Ziarat Masonary check dam)

Abstract
Background and objectives
In my outflow from the stilling basin a significant part of the energy remains,. Therefore, in downstream of stilling basin Local Scour It usually happens. One of the recommended methods to reduce scouring is to use submerged vanes. The review of sources showed that so far no research has been done regarding the use of submerged vanes technique to control scouring in the downstream of stilling basin . On the other hand, according to the research done, physical model has not been used to know masonary check dam and its effects. Therefore, the mentioned items are among the innovations of this research.
Materials and methods
Masonary check dam Tul bene On the Tul Bene River and in 24 kilometers south of city Gorgan with a length of 20 and a elevation of 6 meters and the length of the stilling basin is 10/5 meters. In order to identify the conditions of scour downstream of this structure, the physical model of this structure in the hydraulic laboratory , Gorgan University of Agricultural Sciences and Natural Resources – Pardis. To do this, a concrete channel with a length of 9 meters, a width and a height of one meter has been built. To perform this test, the Masonary check dam of Ziarat madel of metal was modeled according to the facilities of the laboratory on a scale of 1/20. A digital depth gauge with an accuracy of 0.1 millimeters was used to measure the water level, and a bed profile measuring device with an accuracy of 1 millimeters was used to measure the newly created bed topography.experiments at first for Recognizing the tests Conditions downstream scouring masonary check dam ziarat has been carried out during 8 hours with a flow rate of 25 L/S. These tests were performed in three stages to identify the scour volume. In the first stage, the water passes through the overflow and all the pipes, in the next stage, the water enters the pond through the overflow and through the upper pipes. In the last stage, the tests were carried out if the water only passes through the overflow
In order to investigate the effect of submerged vanes on the reduction of scouring of downstream of stilling basin experiments have been conducted with the combination of plates at different angles and distances. In the first stage, plates with an angle of 20 degrees have been used by combining the plates in a converging manner and then in a zigzag manner. In the second step, the angle of the plates was changed to 45 degrees. In this method, firstly, the combination of convergent plates and then the combination of divergent plates have bee used. In the third stage, composite plates are used

Results
The results showed that the best way to reduce scouring is to use divergent submerged vanes with an angle of 45 degrees and use zigzag plates with an angle of 20 degrees, which shows a scouring depth of 25 mm. Since diverging submerged vanes with an angle of 45 will actually wash the walls, the best way to reduce scour is a zigzag angle of 20 degrees.Also, the most scouring occurs in the case of using converging sunken plates with an angle of 20 degrees with a scouring depth of 95 mm.
Conclusion
Submerged vanes change the flow direction. Although these methods have caused less scouring than the base test, in general, in order for the scouring to be close to zero in the downstream of the stilling basin, more tests and different plate placement techniques are needed.