Time-Symmetry of Lagrangian Coherent Structures in Active Turbulence
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866917529186729984 |
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| author | Bellaganti, Suvarchalanjan Manoharan, Amal Kashyap, Kirti Mukherjee, Siddhartha |
| author_facet | Bellaganti, Suvarchalanjan Manoharan, Amal Kashyap, Kirti Mukherjee, Siddhartha |
| contents | Active flows are central to mixing and transport across living systems. While Newtonian fluids remain laminar, diffusive and predictable at the microscale, living fluids like dense bacterial suspensions can exhibit highly chaotic flows like active turbulence, with anomalous transport capabilities. The underlying spatiotemporally persistent structures that drive mixing in active flows, however, remain uncharted. Using Lagrangian Coherent Structures, we now uncover networks of attracting and repelling hyperbolic surfaces. We study changes in the distribution and spectra of Finite-Time Lyapunov Exponent fields in response to increasing activity. Despite the dominance of vorticity in the flow, extreme forward and backward time chaotic mixing is found to originate from straining regions, emphasizing the role of saddles. Fractal dimensions of ridges reveal a morphological simplification of LCS networks with increasing activity, while retaining isotropic crossing. Throughout our work, we also probe a hitherto unasked question-Are signatures of Lagrangian irreversibility manifest in attracting and repelling LCS? To the contrary, we find there is a striking time-symmetry. Our work takes the first steps towards linking flow structures in active turbulence to invariant mixing surfaces. These findings will crucially help in designing activity modulation protocols to seed or inhibit flow structures, and thence mixing, in a bid to tame active turbulence for varied applications. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_25056 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Time-Symmetry of Lagrangian Coherent Structures in Active Turbulence Bellaganti, Suvarchalanjan Manoharan, Amal Kashyap, Kirti Mukherjee, Siddhartha Fluid Dynamics Soft Condensed Matter Chaotic Dynamics Biological Physics Computational Physics Active flows are central to mixing and transport across living systems. While Newtonian fluids remain laminar, diffusive and predictable at the microscale, living fluids like dense bacterial suspensions can exhibit highly chaotic flows like active turbulence, with anomalous transport capabilities. The underlying spatiotemporally persistent structures that drive mixing in active flows, however, remain uncharted. Using Lagrangian Coherent Structures, we now uncover networks of attracting and repelling hyperbolic surfaces. We study changes in the distribution and spectra of Finite-Time Lyapunov Exponent fields in response to increasing activity. Despite the dominance of vorticity in the flow, extreme forward and backward time chaotic mixing is found to originate from straining regions, emphasizing the role of saddles. Fractal dimensions of ridges reveal a morphological simplification of LCS networks with increasing activity, while retaining isotropic crossing. Throughout our work, we also probe a hitherto unasked question-Are signatures of Lagrangian irreversibility manifest in attracting and repelling LCS? To the contrary, we find there is a striking time-symmetry. Our work takes the first steps towards linking flow structures in active turbulence to invariant mixing surfaces. These findings will crucially help in designing activity modulation protocols to seed or inhibit flow structures, and thence mixing, in a bid to tame active turbulence for varied applications. |
| title | Time-Symmetry of Lagrangian Coherent Structures in Active Turbulence |
| topic | Fluid Dynamics Soft Condensed Matter Chaotic Dynamics Biological Physics Computational Physics |
| url | https://arxiv.org/abs/2605.25056 |