Numerical Investigation of Transitional Oscillatory Boundary Layers: Turbulence Quantities

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dc.authorid0000-0002-5917-3542
dc.contributor.authorBaysal, Selman
dc.contributor.authorKirca, V. S. Ozgur
dc.date.accessioned2026-02-03T12:00:00Z
dc.date.available2026-02-03T12:00:00Z
dc.date.issued2025
dc.departmentÇanakkale Onsekiz Mart Üniversitesi
dc.description.abstractThis study investigates the organized flow structures and turbulence quantities in a transitional oscillatory boundary-layer flow over a smooth bed using a DNS model set up by the open-source framework Nektar++ (v5.2.0). The present model was validated against the results of a previous study involving a bypass transition mechanism in the intermittently turbulent regime. To trigger the initial perturbations, a roughness element was placed on the bed and removed at the very moment a two-dimensional vortex tube, caused by an inflectional-point shear-layer instability, was observed on it. Then, the turbulent spots where the flow experienced intense fluctuations in an otherwise laminar boundary layer were identified from the bed shear-stress distribution on the bed, which served as a reliable indicator of turbulence. These flow features emerged as the first sign of the initiation of turbulence. Several measurement points were selected to follow the bed shear-stress variations and to observe the spatial and temporal development of turbulent spots at a low-wave Reynolds number, Re=1.8x105. Along with these observations, phase-resolved turbulence quantities were also investigated over successive half-cycles for the first time in the literature to understand how turbulence develops and spreads over the flow domain. The results show that the turbulence generated in the near-bed region becomes stronger in the deceleration stage due to the adverse pressure gradient and diffuses away from the bed during the subsequent phases of the developing oscillatory boundary-layer flow. The findings related to the turbulence quantities also indicate that the turbulence gradually evolves and spreads into the fluid domain in successive half-cycles.
dc.description.sponsorshipScientific and Technological Research Council of Turkiye (TUBITAK)
dc.description.sponsorship[122M024]
dc.description.sponsorshipThis work was funded by the Scientific and Technological Research Council of Turkiye (TUBITAK) through the project titled Qualitative and Quantitative Investigation of Laminar-to-Turbulent Transition in Steady and Unsteady Boundary Layers under grant No. 122M024.
dc.identifier.doi10.3390/fluids10060143
dc.identifier.issn2311-5521
dc.identifier.issue6
dc.identifier.scopus2-s2.0-105009291206
dc.identifier.scopusqualityQ2
dc.identifier.urihttps://doi.org/10.3390/fluids10060143
dc.identifier.urihttps://hdl.handle.net/20.500.12428/34472
dc.identifier.volume10
dc.identifier.wosWOS:001515649700001
dc.identifier.wosqualityQ3
dc.indekslendigikaynakWeb of Science
dc.indekslendigikaynakScopus
dc.language.isoen
dc.publisherMdpi
dc.relation.ispartofFluids
dc.relation.publicationcategoryMakale - Uluslararası Hakemli Dergi - Kurum Öğretim Elemanı
dc.rightsinfo:eu-repo/semantics/openAccess
dc.snmzKA_WOS_20260130
dc.subjectlaminar-to-turbulent transition
dc.subjectoscillatory boundary layers
dc.subjectdirect numerical simulation
dc.subjectnumerical modeling
dc.subjectturbulent spots
dc.subjectvortex tubes
dc.titleNumerical Investigation of Transitional Oscillatory Boundary Layers: Turbulence Quantities
dc.typeArticle

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