Numerical investigation on the suitability of a fourth-order nonlinear k-ω model for secondary current of second type in open-channels

Mahdad Talebpour, Xiaofeng Liu

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

This study evaluated a typical nonlinear fourth-order k-ω model and the associated roughness boundary condition for their suitability for simulating secondary current of the second kind in open-channels induced by roughness non-uniformity. Three test cases were simulated: square duct flow, open-channel flow with uniformly roughened bed and smooth side walls, and open-channel flow over roughness patches. The nonlinear model and the roughness boundary condition performed relatively well for the first two cases where the corner effect was dominant. For the third case, with alternate roughness patches, strong pressure gradient was generated at the edge between adjacent patches and the secondary current was greatly over-predicted. Two remedial options were tested: increasing the roughness height for smooth walls to a reasonable value and smoothing the roughness transition with a hyperbolic tangent function. We found the first option works better and the second only marginally improves the results.

Original languageEnglish (US)
Pages (from-to)1-12
Number of pages12
JournalJournal of Hydraulic Research
Volume57
Issue number1
DOIs
StatePublished - Jan 2 2019

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roughness
Surface roughness
Open channel flow
open channel flow
boundary condition
Boundary conditions
Hyperbolic functions
Pressure gradient
smoothing
pressure gradient
Ducts

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Water Science and Technology

Cite this

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abstract = "This study evaluated a typical nonlinear fourth-order k-ω model and the associated roughness boundary condition for their suitability for simulating secondary current of the second kind in open-channels induced by roughness non-uniformity. Three test cases were simulated: square duct flow, open-channel flow with uniformly roughened bed and smooth side walls, and open-channel flow over roughness patches. The nonlinear model and the roughness boundary condition performed relatively well for the first two cases where the corner effect was dominant. For the third case, with alternate roughness patches, strong pressure gradient was generated at the edge between adjacent patches and the secondary current was greatly over-predicted. Two remedial options were tested: increasing the roughness height for smooth walls to a reasonable value and smoothing the roughness transition with a hyperbolic tangent function. We found the first option works better and the second only marginally improves the results.",
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