A systematic characterisation of canopy density based on turbulent-structure penetration.
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| Title: | A systematic characterisation of canopy density based on turbulent-structure penetration. |
|---|---|
| Authors: | Chen, Zishen1 (AUTHOR), García-Mayoral, Ricardo1 (AUTHOR) r.gmayoral@eng.cam.ac.uk |
| Source: | Journal of Fluid Mechanics. 4/25/2026, Vol. 1033, p1-41. 41p. |
| Subjects: | Turbulence, Coherent structures, Flow simulations, Reynolds number, Turbulent flow |
| Abstract: | We investigate turbulent flows over canopies of rigid elements with different geometries, spacings and Reynolds numbers to identify and characterise different canopy density regimes. In the sparse regime, the overlying turbulence penetrates relatively unhindered within the canopy, whereas in the dense regime, this penetration is limited. The frontal density, $\lambda _f$ , a common a measure of canopy density, is effective for e.g. conventional vegetation with no preferential orientation, but we observe that it does not fully characterise the density regime for some less conventional topologies, suggesting it may not always capture the underlying physics. To address this, we propose to quantify turbulence penetration directly, from the position and extent of individual turbulent eddies, particularly those associated with intense Reynolds shear stress. We analyse a series of direct simulations for isotropic- and anisotropic-layout canopies with frontal densities $\lambda _f\approx 0.01$ – $2.04$ , heights $h^+\approx 44$ – $266$ , element width-to-pitch ratios $w/s\approx 0.06$ – $0.7$ and Reynolds numbers ${\textit{Re}}_{\tau} \approx 180$ – $2000$. For the same $\lambda _f$ , canopies with elements closely packed in the streamwise direction but large spanwise gaps result in deeper turbulence penetration, appearing sparser than isotropic or spanwise-packed ones. For the same spanwise gap, turbulence penetration remains similar across canopies independently of their streamwise pitch and gap. As the spanwise gap increases, eddies penetrate deeper and more vigorously into the canopy. Turbulence penetration is also Reynolds-number-dependent: the same canopy can behave as dense at low ${\textit{Re}}_{\tau}$ , but increasingly sparse as ${\textit{Re}}_{\tau}$ increases. Our results suggest that turbulence penetration depends essentially on the ability of turbulent eddies to fit within the canopy as they travel downstream, and that this can be characterised by an effective spanwise gap, and its ratio to the typical eddy size; turbulence penetration is substantial when this gap is larger than the eddy size, and negligible in the opposite case. A penetration length $d_p$ can then be defined from the effective gap or the eddy size, whichever is smaller. For small $d_p/h$ , the canopy behaves as dense; for moderate $d_p/h$ , as intermediate; and for $d_p/h\approx 1$ , turbulent eddies can penetrate all the way to the canopy bed and the canopy behaves as sparse. [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: 193952121 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: A systematic characterisation of canopy density based on turbulent-structure penetration. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Chen%2C+Zishen%22">Chen, Zishen</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22García-Mayoral%2C+Ricardo%22">García-Mayoral, Ricardo</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> r.gmayoral@eng.cam.ac.uk</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Fluid+Mechanics%22">Journal of Fluid Mechanics</searchLink>. 4/25/2026, Vol. 1033, p1-41. 41p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Turbulence%22">Turbulence</searchLink><br /><searchLink fieldCode="DE" term="%22Coherent+structures%22">Coherent structures</searchLink><br /><searchLink fieldCode="DE" term="%22Flow+simulations%22">Flow simulations</searchLink><br /><searchLink fieldCode="DE" term="%22Reynolds+number%22">Reynolds number</searchLink><br /><searchLink fieldCode="DE" term="%22Turbulent+flow%22">Turbulent flow</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: We investigate turbulent flows over canopies of rigid elements with different geometries, spacings and Reynolds numbers to identify and characterise different canopy density regimes. In the sparse regime, the overlying turbulence penetrates relatively unhindered within the canopy, whereas in the dense regime, this penetration is limited. The frontal density, $\lambda _f$ , a common a measure of canopy density, is effective for e.g. conventional vegetation with no preferential orientation, but we observe that it does not fully characterise the density regime for some less conventional topologies, suggesting it may not always capture the underlying physics. To address this, we propose to quantify turbulence penetration directly, from the position and extent of individual turbulent eddies, particularly those associated with intense Reynolds shear stress. We analyse a series of direct simulations for isotropic- and anisotropic-layout canopies with frontal densities $\lambda _f\approx 0.01$ – $2.04$ , heights $h^+\approx 44$ – $266$ , element width-to-pitch ratios $w/s\approx 0.06$ – $0.7$ and Reynolds numbers ${\textit{Re}}_{\tau} \approx 180$ – $2000$. For the same $\lambda _f$ , canopies with elements closely packed in the streamwise direction but large spanwise gaps result in deeper turbulence penetration, appearing sparser than isotropic or spanwise-packed ones. For the same spanwise gap, turbulence penetration remains similar across canopies independently of their streamwise pitch and gap. As the spanwise gap increases, eddies penetrate deeper and more vigorously into the canopy. Turbulence penetration is also Reynolds-number-dependent: the same canopy can behave as dense at low ${\textit{Re}}_{\tau}$ , but increasingly sparse as ${\textit{Re}}_{\tau}$ increases. Our results suggest that turbulence penetration depends essentially on the ability of turbulent eddies to fit within the canopy as they travel downstream, and that this can be characterised by an effective spanwise gap, and its ratio to the typical eddy size; turbulence penetration is substantial when this gap is larger than the eddy size, and negligible in the opposite case. A penetration length $d_p$ can then be defined from the effective gap or the eddy size, whichever is smaller. For small $d_p/h$ , the canopy behaves as dense; for moderate $d_p/h$ , as intermediate; and for $d_p/h\approx 1$ , turbulent eddies can penetrate all the way to the canopy bed and the canopy behaves as sparse. [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.2026.11446 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 41 StartPage: 1 Subjects: – SubjectFull: Turbulence Type: general – SubjectFull: Coherent structures Type: general – SubjectFull: Flow simulations Type: general – SubjectFull: Reynolds number Type: general – SubjectFull: Turbulent flow Type: general Titles: – TitleFull: A systematic characterisation of canopy density based on turbulent-structure penetration. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Chen, Zishen – PersonEntity: Name: NameFull: García-Mayoral, Ricardo IsPartOfRelationships: – BibEntity: Dates: – D: 25 M: 04 Text: 4/25/2026 Type: published Y: 2026 Identifiers: – Type: issn-print Value: 00221120 Numbering: – Type: volume Value: 1033 Titles: – TitleFull: Journal of Fluid Mechanics Type: main |
| ResultId | 1 |
