Comparison of turbulence model and wall function couplings for simulating scour

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2022-1-19

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Şentürk, Barış Ufuk

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In this study, the scouring of bed material at the rear side of a rubble mound coastal revetment due to the overtopping of solitary-like waves is numerically studied using a coupled hydrodynamic and morphological computational fluid dynamics model. The major purpose of this thesis study is to investigate the performances of different turbulence model and wall function couplings on the hydrodynamic and morphological results. In the first part of this study, hydrodynamic simulations are performed, and the results are compared in terms of the free surface elevations, overtopping volumes, and jet thicknesses. It is concluded that the simulations that use laminar, 𝑘-𝜔, 𝑘-𝜔 𝑆𝑆𝑇, and stabilized 𝑘-𝜔 𝑆𝑆𝑇 turbulence models show the best agreement with the experimental results. In contrast, the 𝑘-𝜀 and standard 𝑘-𝜔 simulations show the poor ones. Furthermore, it is observed that the use of different wall functions does not affect the hydrodynamic results significantly. In the second part of this study, morphological simulations are carried on, and the results are compared regarding the scour profiles, depths, lengths, and the distance of the deepest point to the crown wall. In conclusion, the 𝑘-𝜔 turbulence model with Fuhrman et al. (2014) wall function simulation shows the best agreement with the experimental result to capture the scour profile and depth. Furthermore, laminar, 𝑘-𝜔 𝑆𝑆𝑇, stabilized 𝑘-𝜔 𝑆𝑆𝑇, and 𝑘-𝜔 with Fuhrman et al. (2014) wall function simulations match well with the experimental result regarding the scour length and the distance from the crown wall, while the other simulations do not show good agreements. It is also observed that suspended sediment transport is a significant contributor to the scour in the present study.

Subject Keywords

Computational fluid dynamics, Porous media modeling, Turbulence modeling, Wall functions, Scour

URI

https://hdl.handle.net/11511/96048

Collections

Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

B. U. Şentürk, “Comparison of turbulence model and wall function couplings for simulating scour,” M.S. - Master of Science, Middle East Technical University, 2022.