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Title: Numerical investigation of alternating skimming flow over a stepped spillway
Authors: Kaouachi, Anouar
Carvalho, Rita F. 
Lopes, Pedro 
Benmamar, Saâdia
Gafsi, Moustefa
Keywords: alternating skimming flow; computational fluid dynamics; numerical modelling; stepped spillway
Issue Date: 2021
Project: FCT Project UIDB/04292/2020 – MARE 
MESRS (Ministry of Higher Education and Scientific Research, Algeria) through the scholarship PNE 
Serial title, monograph or event: Water Supply
Volume: 21
Issue: 7
Abstract: This study aims to illustrate the influence of stepped spillway width on alternating skimming flow development. A computational fluid dynamics (CFD) model in Ansys Fluent® was established to simulate the flow over stepped spillways, using a volume of fluid model (VOF) and Reynolds Averaged Navier–Stokes (RANS) turbulence model (SST k-ω). The model was first validated by comparisons of velocity profiles at step niches and water depth at step edges with existing measurements acquired by the bubble image velocimetry (BIV) technique and an ultrasonic sensor, in a 0.5-m wide stepped spillway physical model. The SST k-ω model gave good results for velocity and water depth, and the numerical predictions of the vorticity in the skimming and recirculating flows were qualitatively adequate. The model was used to analyse the flow regime for six different stepped spillway widths. The careful examination of flow patterns at the different stepped spillway widths showed that the alternating skimming flow appears for the stepped spillways wider than 0.35 m due to the asymmetrical distribution of vorticity patches that are generated in the step cavity. These vorticity patches are of uniform size and shape when the spillway width is less than 0.35 m, which does not produce an alternating skimming flow. However, for wider stepped spillways, the vorticity increases, and an alternating skimming flow appears closer to the crest.
ISSN: 1606-9749
DOI: 10.2166/ws.2021.141
Rights: openAccess
Appears in Collections:I&D MARE - Artigos em Revistas Internacionais

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