Spectral analysis of attached and separated turbulent flows over a Gaussian-shaped bump.
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| Title: | Spectral analysis of attached and separated turbulent flows over a Gaussian-shaped bump. |
|---|---|
| Authors: | Klopsch, Roman1,2 roman.klopsch24@imperial.ac.uk, Fuchst, Lukas M.2, Rigas, Georgios1, Oberleithner, Kilian2, von Saldern, Jakob G. R.2 |
| Source: | Journal of Fluid Mechanics. 6/10/2026, Vol. 1036, p1-34. 34p. |
| Subjects: | Flow separation, Coherent structures, Frequency response, Turbulent flow, Frequency-domain analysis |
| Abstract: | We investigate the broadband turbulent dynamics of attached and separated flows over a Gaussian bump, focusing on the origin of low-frequency coherent structures. The analysis combines time-resolved experimental measurements with physics-based linear models, using mean fields previously assimilated from the same dataset as base flows. Spectral proper orthogonal decomposition reveals a coherent dynamics in low- and medium-frequency regimes for both flows, with the low-frequency dynamics being substantially stronger in the separated case. In the separated flow, this dynamics is linked to a three-dimensional zero-frequency modal instability that generates large-scale streamwise-elongated structures downstream of the bump. A standing-wave model based on resolvent modes, incorporating finite-span effects, reproduces the experimentally observed spanwise structure of the dynamics and highlights the limitations of simulations with small spanwise extent and periodic boundary conditions. In the attached flow, similar low-frequency structures are identified. These are weaker, do not form a prominent standing-wave pattern and cannot be definitively classified as either modal or non-modal. The three-dimensional zero-frequency instability and finite-span standing-wave dynamics are identified as the main drivers of low-frequency coherent structures in the separated flow. They offer an explanation for persistent discrepancies between simulations and experiments on the Gaussian bump, and provide guidance on spanwise domain size and boundary conditions for future simulations. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Fluid Mechanics is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 194752287 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Spectral analysis of attached and separated turbulent flows over a Gaussian-shaped bump. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Klopsch%2C+Roman%22">Klopsch, Roman</searchLink><relatesTo>1,2</relatesTo><i> roman.klopsch24@imperial.ac.uk</i><br /><searchLink fieldCode="AR" term="%22Fuchst%2C+Lukas+M%2E%22">Fuchst, Lukas M.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Rigas%2C+Georgios%22">Rigas, Georgios</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Oberleithner%2C+Kilian%22">Oberleithner, Kilian</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22von+Saldern%2C+Jakob+G%2E+R%2E%22">von Saldern, Jakob G. R.</searchLink><relatesTo>2</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Fluid+Mechanics%22">Journal of Fluid Mechanics</searchLink>. 6/10/2026, Vol. 1036, p1-34. 34p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Flow+separation%22">Flow separation</searchLink><br /><searchLink fieldCode="DE" term="%22Coherent+structures%22">Coherent structures</searchLink><br /><searchLink fieldCode="DE" term="%22Frequency+response%22">Frequency response</searchLink><br /><searchLink fieldCode="DE" term="%22Turbulent+flow%22">Turbulent flow</searchLink><br /><searchLink fieldCode="DE" term="%22Frequency-domain+analysis%22">Frequency-domain analysis</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: We investigate the broadband turbulent dynamics of attached and separated flows over a Gaussian bump, focusing on the origin of low-frequency coherent structures. The analysis combines time-resolved experimental measurements with physics-based linear models, using mean fields previously assimilated from the same dataset as base flows. Spectral proper orthogonal decomposition reveals a coherent dynamics in low- and medium-frequency regimes for both flows, with the low-frequency dynamics being substantially stronger in the separated case. In the separated flow, this dynamics is linked to a three-dimensional zero-frequency modal instability that generates large-scale streamwise-elongated structures downstream of the bump. A standing-wave model based on resolvent modes, incorporating finite-span effects, reproduces the experimentally observed spanwise structure of the dynamics and highlights the limitations of simulations with small spanwise extent and periodic boundary conditions. In the attached flow, similar low-frequency structures are identified. These are weaker, do not form a prominent standing-wave pattern and cannot be definitively classified as either modal or non-modal. The three-dimensional zero-frequency instability and finite-span standing-wave dynamics are identified as the main drivers of low-frequency coherent structures in the separated flow. They offer an explanation for persistent discrepancies between simulations and experiments on the Gaussian bump, and provide guidance on spanwise domain size and boundary conditions for future simulations. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of Fluid Mechanics is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1017/jfm.2026.11629 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 34 StartPage: 1 Subjects: – SubjectFull: Flow separation Type: general – SubjectFull: Coherent structures Type: general – SubjectFull: Frequency response Type: general – SubjectFull: Turbulent flow Type: general – SubjectFull: Frequency-domain analysis Type: general Titles: – TitleFull: Spectral analysis of attached and separated turbulent flows over a Gaussian-shaped bump. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Klopsch, Roman – PersonEntity: Name: NameFull: Fuchst, Lukas M. – PersonEntity: Name: NameFull: Rigas, Georgios – PersonEntity: Name: NameFull: Oberleithner, Kilian – PersonEntity: Name: NameFull: von Saldern, Jakob G. R. IsPartOfRelationships: – BibEntity: Dates: – D: 10 M: 06 Text: 6/10/2026 Type: published Y: 2026 Identifiers: – Type: issn-print Value: 00221120 Numbering: – Type: volume Value: 1036 Titles: – TitleFull: Journal of Fluid Mechanics Type: main |
| ResultId | 1 |
