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Abstract
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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.
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