Accuracy and comparison of standard k-ϵ with two variants of k-ω turbulence models in fluvial applications

Abstract

Racetrack flumes are established experimental settings in ecohydraulics and sediment studies. Their experimental results are often coupled with numerical simulations. The two-equation turbulence closures of the Reynolds-Averaged Navier-Stokes equations are applied widely in such engineering applications. They are preferred for their ease of use and low computational costs compared with more sophisticated turbulence models involving large-scale fluvial simulations. Here, three variants of two-equation models, i.e. the standard k-ε model and two variants of k-ω models, were applied to tackle mean flow and turbulence in a racetrack flume and a river reach. Regarding model performances, we found an overall reasonable agreement between simulated and measured mean velocity values. Nonetheless, the simulated turbulent kinetic energy exhibited discrepancies to the measured values. The computational costs of all investigated model variants are comparable. Therefore, there is no significant preference among models. The findings confirm the application of these model approaches for mean flow-related investigations (e.g. habitat modeling) but suggest exercising caution for applications sensitive to turbulent processes. ARTICLE HISTORY

Experiments on turbulence and near bank vorticities in an open channel sharp bend

“…This is particularly evident for outer bank zones (dark shadow squares in the Figures 4-6). The applicability of the simplified equation of streamwise vorticity was already questioned with regard to the main cell of secondary flows for strongly curved channels [5,7]. The comparison presented in this work, therefore, reaffirms the inadequacy of this equation in order to estimate outer bank zone vorticities.…”

“…We already presented the simplified downstream vorticity equation (equation 1), which is widely applied in linear models [7]. Linear models do not consider nonlinear feedback between downstream velocity profiles and cells of secondary flow; this often leads to misestimation of vorticty and three-dimensionality in bends [5].…”

“…This equation is widely applied in classical hydraulic and engineering practices. Despite the wide usage and good results out of this equation in case of mild bends, there are important concerns about their applicability to the sharp bends [5,6,7]. Here, based on a term-by-term approach, the range of discrepancies between the simplified equation (i.e.…”

Numerical simulation of thermal pollution zones’ formations in the water environment from the activities of the power plant

“…(1) the k-turbulence model. This is a two-parameter model that gives a general description of turbulence using two transport equations (Farhadi, Mayrhofer, Tritthart, Glas, & Habersack, 2018;Issakhov, Bulgakov, & Zhandaulet, 2019a, 2019b; (2) the k-ω turbulence model is a two-parameter general turbulence model, which is used as the closure for the Reynolds-averaged Navier-Stokes equations (Issakhov & Mashenkova, 2019); (3) The idea of the large eddy simulation method is that the velocity components are divided into the resolved and sub-grid parts. The resolved velocity is simulated by 'large' eddies, and the sub-grid part of the velocity is modeled by 'small scales'.…”

Flow-induced vibration of a radial gate at various opening heights

“…Zhang, Jiang, & Ye, 2007), complex flows in irregular domains (Fadlun, Verzicco, Orlandi, & Mohd-Yusof, 2000;Udaykumar, Mittal, Rampunggoon, & Khanna, 2001), and turbulence (Kaligzin & Iaccarino, 2003;Yang & Balaras, 2006). Furthermore, hydraulic modeling case studies such as the diffusion prediction of pollutants (Chau & Jiang, 2002, asymmetric orifice design in a surge tank (Gabl & Righetti, 2018), turbulence simulation in fluvial applications (Farhadi, Mayrhofer, Tritthart, Glas, & Habersack, 2018), and the mathematical modeling of water quality rehabilitation (Wu & Chau, 2006) have all been conducted using advanced CFD methods.…”