The structure of vortical flow over a rounded broad-crested weir


Kızılaslan M. A., Atlas E. D., Yaban H., Demirel E.

arxiv, pp.1-19, 2023 (Peer-Reviewed Journal) identifier

  • Publication Type: Article / Article
  • Publication Date: 2023
  • Journal Name: arxiv
  • Page Numbers: pp.1-19
  • Çanakkale Onsekiz Mart University Affiliated: Yes

Abstract

Turbulent flow over a rounded broad-crested weir is investigated by means of detached eddy simulation (DES) with special emphasis on the interaction of coherent vortex structures with free-surface. In order to set up and validate the computational model, experimental studies were conducted in a laboratory flume using a moderately rounded broad-crested weir with a rounding ratio of R/P=0.15, where R is the radius of the upstream nose and P is the height of the weir. The simulated mean velocity and free-surface profiles show good agreement with the experimental measurements. Numerical results are evaluated for identifying boundary layer development, vortex structures and wave propagation over the crest of the weir for different discharges. Spatial variation of the boundary layer on the crest is well captured using a dimensionless form of the Lamb vector divergence. A horseshoe vortex system emanating from the bottom of the channel interacts with the free-surface at the entrance of the crest causing undulation on the free-surface. Unsteady characteristics of the flow are examined in terms of the PSD of vortex-induced forces acting on the weir. It is found that a free-surface boundary layer develops from the undulation to the wall boundary layer on the crest. It was revealed the hat installation of an artificial pool upstream of the weir significantly modified vortex structures and reduced undulation effects by 79.1% according to a proposed undulation index.