This study presents the use of wall y+ approach as guidance for reliable mesh and turbulence model selection in bent pipe flow investigations.&nbsp; The research builds on previous studies recommendation by Salim et al.[1]–[3] for using wall y+ approach to balance between the computational cost and time, especially where the experimental data are difficult to obtain. In those previous studies, it is observed that, generating a higher mesh resolution (fine mesh) does not necessarily always mean that it will provide a high accurate numerical solution. In some cases, resolving into the log-law region (y+ &gt; 30) produces better results than resolving all the way into the viscous sublayer (y+ &lt; 5).The main purpose of the wall y+ approach implementation in this current study, is to use it as guidance for reliable mesh and turbulence model selection in bent pipe flow studies. This approach is proposed to reduce the time spent on the grid independence test which involves time-consuming procedures. This method is proposed as an effective tool for selecting an appropriate near wall treatment and corresponding turbulence model and remove the necessity of physical validation when experimental data is unavailable or difficult to obtain.Flow in a 90-degree pipe elbow is modelled using the ANSYS FLUENT CFD solver to evaluate the performance of different Reynolds-Averaged Naiver-Stokes (RANS) turbulence models. The RANS models tested are the standard k-ε, the Reynolds Stress Model (RSM), the k–ω Shear Stress Transport (SST) and the Spalart–Allmaras. A range of near wall spatial resolutions is used to determine the effectiveness of near wall modelling techniques when used in conjunction with each of the turbulence models. The near-wall treatments are investigated by solving the y+ values for the first layer of cells are in the viscous sublayer (y+≈3), buffer region (y+ ≈19) and log law region (y+≈39).The achieved results in this current study using the wall y+ approach are compared against published experimental data by Sudo et al.[4] &nbsp;and numerical simulations by Kim et al.[5]. Qualitative analysis and quantitative assessment are carried out to investigate which turbulence model agrees best with the published data. It is observed that the near wall models provide better results when the y+ values for the first layer of near wall cells are within viscous sublayer in comparison to simulations where it is in the buffer and log-low regions. The RSM predicts the flow field most accurately when compared against the reference data, particularly in the secondary flow region where the flow is affected by the elbow.&nbsp; The wall y+ approach is useful tool in selecting a reliable mesh and corresponding turbulence model for predicting flow field in bent pipe with balance between the computational cost and time. This in turn will allow pipeline designers to assess the effectiveness of their design, and any potential problems with it, before the manufacturing stage.ReferencesS. M. Salim and S. Cheah, “Wall Y strategy for dealing with wall-bounded turbulent flows,”J. Kim, M. Yadav, and S. Kim, “Characteristics of Secondary Flow Induced by 90-Degree Elbow in Turbulent Pipe Flow,”K. Sudo,&nbsp;“Experimental investigation on turbulent flow in a circular-sectioned 90-degree bend,”

Numerical Simulation of Turbulent Pipe Flow With 90-Degree Elbow Using Wall y+ Approach Simulation of Turbulent Pipe Flow With 90-Degree Elbow Using Wall y+ Approach

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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