Vortex interactions and wake transitions for flexible foil flapping in flowing soap film.
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| Title: | Vortex interactions and wake transitions for flexible foil flapping in flowing soap film. |
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| Authors: | Patel, Sarthak K.1, Shinde, Sachin Yashavant1 sachin@iitk.ac.in |
| Source: | Journal of Fluid Mechanics. 3/25/2026, Vol. 1031, p1-23. 23p. |
| Subjects: | Vortex shedding, Flexural modulus, Vortex motion, Fluid dynamics |
| Abstract: | Understanding the vortex interactions and wake transitions for flapping flexible foils is important because of their increased usage in bioinspired aquatic and aerial robotic propulsors. Although wake transitions have been studied for rigid foils, we experimentally investigate how flexibility alters the transitions and vortex interactions for flexible foils, which are closer to the natural flapping foils in fish, birds and insects. We conduct the experiments in a flowing soap film on a pitching airfoil with a flexible filament at its trailing edge (TE). We find that, apart from the Strouhal number (St), flexural rigidity (EI) is important to determine the transitions. We vary EI of the flexible filament by three orders of magnitude and also investigate an extreme case of EI→∞. Flexibility triggers the shedding of multiple small 'secondary vortices' (SVs) along with big 'primary vortices' (PVs), unlike only PVs for the rigid foil. Continuous deformations of the flexible filament play crucial roles in determining the interaction of boundary layer vortices and trailing edge vortices and, ultimately, the generation and evolution of PVs and SVs. We identify five vortex interaction mechanisms (VIMs). Depending on how SVs interact with PVs, the wake assumes different patterns. We construct the St-EI phase maps for wake transitions and newly identified VIMs. We devise a non-dimensional parameter γ, referred to as 'Yashavant number'. One order increase in γ reduces the number of VIMs by one. Instead of following the usual transition route, the flexible foil reveals counterintuitive transition trends that strongly depend on the filament EI. [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: 192858594 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Vortex interactions and wake transitions for flexible foil flapping in flowing soap film. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Patel%2C+Sarthak+K%2E%22">Patel, Sarthak K.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Shinde%2C+Sachin+Yashavant%22">Shinde, Sachin Yashavant</searchLink><relatesTo>1</relatesTo><i> sachin@iitk.ac.in</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Fluid+Mechanics%22">Journal of Fluid Mechanics</searchLink>. 3/25/2026, Vol. 1031, p1-23. 23p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Vortex+shedding%22">Vortex shedding</searchLink><br /><searchLink fieldCode="DE" term="%22Flexural+modulus%22">Flexural modulus</searchLink><br /><searchLink fieldCode="DE" term="%22Vortex+motion%22">Vortex motion</searchLink><br /><searchLink fieldCode="DE" term="%22Fluid+dynamics%22">Fluid dynamics</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Understanding the vortex interactions and wake transitions for flapping flexible foils is important because of their increased usage in bioinspired aquatic and aerial robotic propulsors. Although wake transitions have been studied for rigid foils, we experimentally investigate how flexibility alters the transitions and vortex interactions for flexible foils, which are closer to the natural flapping foils in fish, birds and insects. We conduct the experiments in a flowing soap film on a pitching airfoil with a flexible filament at its trailing edge (TE). We find that, apart from the Strouhal number (St), flexural rigidity (EI) is important to determine the transitions. We vary EI of the flexible filament by three orders of magnitude and also investigate an extreme case of EI→∞. Flexibility triggers the shedding of multiple small 'secondary vortices' (SVs) along with big 'primary vortices' (PVs), unlike only PVs for the rigid foil. Continuous deformations of the flexible filament play crucial roles in determining the interaction of boundary layer vortices and trailing edge vortices and, ultimately, the generation and evolution of PVs and SVs. We identify five vortex interaction mechanisms (VIMs). Depending on how SVs interact with PVs, the wake assumes different patterns. We construct the St-EI phase maps for wake transitions and newly identified VIMs. We devise a non-dimensional parameter γ, referred to as 'Yashavant number'. One order increase in γ reduces the number of VIMs by one. Instead of following the usual transition route, the flexible foil reveals counterintuitive transition trends that strongly depend on the filament EI. [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.2026.11290 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 23 StartPage: 1 Subjects: – SubjectFull: Vortex shedding Type: general – SubjectFull: Flexural modulus Type: general – SubjectFull: Vortex motion Type: general – SubjectFull: Fluid dynamics Type: general Titles: – TitleFull: Vortex interactions and wake transitions for flexible foil flapping in flowing soap film. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Patel, Sarthak K. – PersonEntity: Name: NameFull: Shinde, Sachin Yashavant IsPartOfRelationships: – BibEntity: Dates: – D: 25 M: 03 Text: 3/25/2026 Type: published Y: 2026 Identifiers: – Type: issn-print Value: 00221120 Numbering: – Type: volume Value: 1031 Titles: – TitleFull: Journal of Fluid Mechanics Type: main |
| ResultId | 1 |
