An axisymmetric model for draft tube flow at partial load

Hosein Foroutan, Savas Yavuzkurt

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

A new Reynolds-averaged Navier-Stokes (RANS) turbulence model is developed in order to correctly predict the mean flow field in a draft tube operating under partial load using 2-D axisymmetric simulations. It is shown that although 2-D axisymme- tric simulations cannot model the 3-D unsteady features of the vortex rope, they can give the average location of the vortex rope in the draft tube. Nevertheless, RANS simulations underpredict the turbulent kinetic energy (TKE) production and diffusion near the center of the draft tube where the vortex rope forms, resulting in incorrect calculation of TKE profiles and, hence, poor prediction of the axial velocity. Based on this observation, a new k-ϵ turbulence RANS model taking into account the extra production and diffusion of TKE due to coherent structures associated with the vortex rope formation is developed. The new model can successfully predict the mean flow velocity with significant improvements in comparison with the realizable k-ϵ model. This is attributed to better prediction of TKE production and diffusion by the new model in the draft tube under partial load. Specifically, the new model calculates 31% more production and 46% more diffusion right at the shear layer when compared to the k-ϵ model.

Original languageEnglish (US)
Pages (from-to)195-205
Number of pages11
JournalJournal of Hydrodynamics
Volume28
Issue number2
DOIs
StatePublished - Apr 1 2016

Fingerprint

draft
Pipe flow
Tube
tubes
Partial
Kinetic energy
Vortex
Vortex flow
kinetic energy
Navier-Stokes
vortices
Model
Predict
Simulation
Coherent Structures
simulation
Prediction
turbulence models
shear layers
Turbulence Model

All Science Journal Classification (ASJC) codes

  • Modeling and Simulation
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Foroutan, Hosein ; Yavuzkurt, Savas. / An axisymmetric model for draft tube flow at partial load. In: Journal of Hydrodynamics. 2016 ; Vol. 28, No. 2. pp. 195-205.
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abstract = "A new Reynolds-averaged Navier-Stokes (RANS) turbulence model is developed in order to correctly predict the mean flow field in a draft tube operating under partial load using 2-D axisymmetric simulations. It is shown that although 2-D axisymme- tric simulations cannot model the 3-D unsteady features of the vortex rope, they can give the average location of the vortex rope in the draft tube. Nevertheless, RANS simulations underpredict the turbulent kinetic energy (TKE) production and diffusion near the center of the draft tube where the vortex rope forms, resulting in incorrect calculation of TKE profiles and, hence, poor prediction of the axial velocity. Based on this observation, a new k-ϵ turbulence RANS model taking into account the extra production and diffusion of TKE due to coherent structures associated with the vortex rope formation is developed. The new model can successfully predict the mean flow velocity with significant improvements in comparison with the realizable k-ϵ model. This is attributed to better prediction of TKE production and diffusion by the new model in the draft tube under partial load. Specifically, the new model calculates 31{\%} more production and 46{\%} more diffusion right at the shear layer when compared to the k-ϵ model.",
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An axisymmetric model for draft tube flow at partial load. / Foroutan, Hosein; Yavuzkurt, Savas.

In: Journal of Hydrodynamics, Vol. 28, No. 2, 01.04.2016, p. 195-205.

Research output: Contribution to journalArticle

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