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Title: Numerical Study of the Separation and Reattachment Points of Openchannel Flow over Backwards-Facing Step using OpenFOAM

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Title:
Numerical Study of the Separation and Reattachment Points of Openchannel Flow over Backwards-Facing Step using OpenFOAM
Author Name:
Getachew Tegegne Damtew
Abstract:
This paper presents the numerical study of the separation and reattachment points of flow over backwards-facing step openchannel. A numerical analysis is performed using OpenFOAM to investigate backward-facing step flow for Reynolds numbers in the turbulent regions. A numerical investigation is conducted on the affect of Reynolds number on the separation and attachment points for backward-facing step flow. The expansion ratio of outlet height to inlet height of 2.0 is considered for this study. This study also consider the two commonly used RANS turbulence models namely , and model. Flow over a backward-facing step produces recirculation zones where the fluid separates and forms vortices. For turbulent flow, the fluid separates at the step and reattaches downstream. Only a single recirculation zone develops for turbulent flow and the reattachment point is believed to be independent of the Reynolds number and depend only on the ratio of inlet height to outlet height. For the coarser mesh the reattachment point almost similar for the two turbulence model and the length of separation zone is about 2.7 m. For the finer mesh the reattachment point in the case of k – epsilon model is bigger than k – omega model and the length of separation zone is about 3m for k – epsilon model and 2 m for k – omega model. The maximum magnitude of velocity is about 7.2 m/s for both models and it occurs initially near the step.
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