Improvement of Hydraulic Performance of Nonlinear Piano-key Weirs in Plan

In this research, the way for improve performance and also increase the discharge coefficient of curvilinear piano-key weir in plan was investigated. For this purpose, changes in the geometric shape of this type of weir have been created and the results of these changes have been investigated using the FLOW3D software. One of these changes is the deformation of the weir crown. Therefore three weir models with rectangular, triangular and elliptical crowns were designed. Results showed that weir with triangular crown had up to 60% higher discharge coefficient than the elliptical-crown weir and up to 65% more than the rectangular-crown weir. In the second part of this research, effect of existence or absence, as well as the geometric shape of the bundle, on the performance of these types of weirs was investigated. For this purpose, three weir models with cubic rectangular, half-cylindrical and prism bundles were designed and compared with a weir without bundle. The results showed that in low flow rates, the bundle improved the hydraulic performance of the weir and also among the bundles, half-cylindrical bundle had better performance than other bundles, but by increasing pass discharge, the effect of bundle operation decreased, and gradually the discharge coefficient of weir with bundle and weir without bundle approached. Finally, the impact of parapet wall on these types of weirs operation was investigated. For this purpose, a 1.3 cm high parapet wall was added to the weir crown. Results showed that this action increased the discharge coefficient by about 7%. Generally, in high flow heads, the improvement factors do not have a significant effect on weir performance.