جستجوی مقالات مرتبط با کلیدواژه "آبشکن های سری" در نشریات گروه "آب و خاک"

Among the approaches to reduce flood damage is to reduce the flow rate near the shore by spur dikes. The study first simulated the transfer of sediment and scour around series spur dikes in an experimental model using Flow 3d software. According to the comparison results, one can observe a good match between the results of the numerical and experimental models that the error rates of MAPE around the first spur dike, for U/Ucr ratios were, 0.75, 0.85 and 0.95 and were 9%, 13.79% and 14.10%, respectively. Then two protective spur dikes with various lengths (10 and 20 cm) were used in canal upstream and the effects of the presence of these two protective spur dikes simultaneously on the scour around the main spur dike were examined. In modeling done, increase in U/Ucr depth increases the maximum spur dike depth, so that with increase in U/Ucr by 26% (from 0.75 to 0.95), the increase in the maximum depth of the first spur was 51%, in the second spur dike 4 times, and in the third spur dike 116%. When the protective spur dike couple with various lengths is used simultaneously, and then these two protective spur dikes simultaneously drastically reduce the effect of the flow intensity to the wall and nose of the main spur dike. Moreover, the maximum depth of scour around the

Generally, due to the presence secondary flows in the curvature of the river, the outer wall in the bend is always subjected to degradation and erosion. These streams divert the surface flow lines towards the outer wall and the flow lines close to the substrate to the inner wall. Therefore, studying the flow in the meandering channels in order to prevent erosion is of particular importance. One of the simplest, yet most economic methods to cope with outer wall erosion is the use of spur dike. For this purpose, in this laboratory study, the effect of the presence and absence of series spur dikes on longitudinal velocity components in a channel meandering with sloped erodible wall is investigated. The results showed that the presence of simple series spur dikes cause reduced the flow velocity in the outer wall of the bend. Therefore, the average highest velocity reduction between the second and third spur dikes and the lowest velocity reduction between the third and fourth spur dikes was performed. Also, the studies showed that with the increase of 33% of the discharge, about 5% were added to the performance of the spur dikes in reducing the flow velocity in the outer wall of bend.

The river is an active natural phenomenon, which continuously changes its sides and its bed. This has caused the river course to undergo major changes over time. There are different ways to reduce erosion, one of the ways is using spur dike in sides. In this experimental study, the effect of simple L and T shapes series spur dike on time variation of scour depth around spur dike was analyzed and compared under straight channel condition. The results showed that T shape spur dike within 10% of elapsed time reaches to more than 90% of equilibrium scouring, whereas for simple and L shape spur dike within 15% of elapsed time reaches to more than 80% of equilibrium scouring or erosion. Simple and L shape spur dike had the maximum scouring depth which was found to be equivalent to 3times of the flow depth, which was created a bit behind the spur dike's nose. The scouring of T shaped spur dike was 0.3y (y is flow depth) less than other shapes in first position. The results of scour depth comparison in different section around the spur dikes showed that the average of scouring value for T-shaped spur dike was 0.4y and 0.25y less than simple and L-shaped spur dike, respectively. Finally, an equation for calculation of time variation of scour depth due to the shape of the spur dike is proposed. Further, the experimental results of scouring depth as a result of present study was compared with results obtained by other researchers. Also maximum side erosion on the opposite shore was found to belong to L-shaped spur dike.