Application of VOF and k-epsilon turbulence model in simulation of flow over a bottom aerated ramp and step structure

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Tokyay T., Kurt C.

WATER SA, vol.45, no.2, pp.278-290, 2019 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 45 Issue: 2
  • Publication Date: 2019
  • Doi Number: 10.4314/wsa.v45i2.15
  • Journal Name: WATER SA
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.278-290
  • Keywords: jet-length, aerator, VOF, air-entrainment, ramp, computational fluid dynamic, AIR ENTRAINMENT, CAVITATION
  • Middle East Technical University Affiliated: Yes


A three-dimensional numerical model of ANSYS, Fluent (2011) was employed for studying mid to high discharge supercritical two-phase flow over a single slope spillway with a single step for aeration of the flow. In this study 18 simulations were conducted using the Volume of Fluid (VOF) method for air-water interface tracking and simple k-epsilon model for turbulence closure. Submerged circular shaped pipes located at the bottom of the step were utilized as aerators. Analyses concentrate on the air-entrainment phenomenon and jet-length of the flow from the step to the re-attachment point. The variables considered in the study are discharge, aerator size, different aerator arrangements, Froude number of the flow, presence of a ramp before the step and its angle. Observed jet-length values in this study were compared with two sets of empirical formulae from literature for code validation. Cross-sectional average of air concentration due to bottom aeration was determined in the streamwise direction downstream of the re-attachment of the jet. The air concentration is observed to follow a logarithmic decay in the flow direction within the de-aeration zone.