Experimental and Numerical Study of the Effect of Zigzag Crests with Various Geometries on the Performance of A-type Piano Key Weirs

In the present study, the discharge capacity and the hydrodynamic behavior of A-type piano key weirs with simple crests and non-simple crests with zigzag indentations in various geometries, including triangular, rectangular, trapezoidal, and semi-circular zigzag crests, were investigated. First, using laboratory data and results of numerical simulation with Flow-3D software, the discharge capacity and the discharge coefficient of the weirs were determined and discussed. Then flow configuration over the weirs was studied in different submersion conditions. For this purpose, the formations of the streamlines passing over the weirs were extracted from the numerical results and were analyzed after matching with the laboratory observations. Furthermore, the energy dissipations of the weirs were calculated using the numerical results, and the effect of the geometry of the crests on the energy loss of the weirs was investigated. The results demonstrate that in relative water heads less than 0.5, the zigzag indentations of the lateral crests cause substantial increases in the discharge capacity and the energy dissipation of PKWs, though in higher relative water heads the geometry of the crest has no significant effect on the hydraulic behavior of weirs. Among all modified weirs, the PKW with semi-circular indentations has the best performance in terms of both discharge capacity and energy dissipation. For instance, in a relative water load of 0.07 the discharge capacity of this weir is more than twice that of the simple weir.