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arXiv · 2609.23273

Cascade-driven fragmentation-aggregation transitions in decaying turbulence

Vivek Kumar·Prasoon Suchandra·Shivam Prajapati·Suhas Jain·Cyrus Aidun
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Abstract

In decaying turbulence, the turbulent cascade is not merely a passive background for breakup but an evolving stability boundary that dynamically selects the fragmentation-aggregation pathway. As turbulence decays, the Hinze scale sweeps through the bubble-size distribution, progressively eliminating the breakable population and driving a transition from a mixed breakup-coalescence regime to a self-sustaining pure-coalescence state. Our model predicts a critical turbulence decay exponent $m=5/3$, a transient mixed breakup-coalescence regime, and a late-stage pure-coalescence state with a universal coalescence hazard. Interestingly, the transient breakup acts as a catalyst that amplifies mixed-regime bubble growth relative to pure coalescence. Results from our direct numerical simulations of decaying homogeneous isotropic turbulence as well as high-Reynolds-number duct-flow experiments collapse onto the model predictions when expressed in terms of the measured decay rate. These results replace the conventional instantaneous Hinze criterion with a non-equilibrium, cascade-controlled framework for turbulent fragmentation and aggregation.

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Vivek Kumar, Prasoon Suchandra, Shivam Prajapati, Suhas Jain, Cyrus Aidun. 2026-09-20. Cascade-driven fragmentation-aggregation transitions in decaying turbulence. https://arxiv.org/abs/2609.23273

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