Simplified Transition and Turbulence Modeling for Oscillatory Pipe Flows

Alexander Shapiro, Gershon Grossman and David Greenblatt
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Alexander Shapiro: Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, Technion City, Haifa 320003, Israel
Gershon Grossman: Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, Technion City, Haifa 320003, Israel
David Greenblatt: Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, Technion City, Haifa 320003, Israel

Energies, 2021, vol. 14, issue 5, 1-19

Abstract: One-dimensional unsteady Reynolds-averaged Navier–Stokes computations were performed for oscillatory transitional and turbulent pipe flows and the results were validated against existing experimental data for a wide variety of oscillatory Reynolds and Womersley numbers. An unsteady version of the Johnson–King model was implemented with optional near-wall modification to account for temporal pressure gradient variations, and the predictions were compared with those of the Spalart–Allmaras and k – ε turbulence models. Transition and relaminarization were based on empirical Womersley number correlations and assumed to occur instantaneously: in the former case, this assumption was valid, but in the latter case, deviations between data and predictions were observed. In flows where the oscillatory Reynolds numbers are substantially higher than the commonly accepted steady critical value (~2000), fully or continuously turbulent models produced the best correspondence with experimental data. Critically and conditionally turbulent models produced slightly inferior correspondence, and no significant benefit was observed when near-wall pressure gradient effects were implemented or when common one- and two-equation turbulence models were employed. The turbulent velocity profiles were mainly unaffected by the oscillations and this was explained by noting that the turbulent viscosity is significantly higher than its laminar counterpart. Thus, a turbulent Womersley number was proposed for the analysis and categorization of oscillatory pipe flows.

Keywords: pulse-tube cryogenic coolers; unsteady turbulent flow; pipe flow; turbulence modeling; Womersley number (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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