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Soft transition between subcritical and supercritical currents through intermittent cascading interfacial
Jorge Salinas1, S Balachandar2, Mrugesh Shringarpure3
1Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611; josalinas@ufl.edu.
Summary
Highly resolved simulations reveal how bed slope affects gravity currents. A new transcritical regime with intermittent instabilities was identified, driven by departures from equilibrium.
Area of Science:
- Fluid dynamics
- Geophysics
- Turbulence modeling
Background:
- Gravity currents are density-driven flows crucial in geophysical and industrial settings.
- Understanding their long-range propagation and interfacial dynamics is key.
Purpose of the Study:
- To investigate the impact of bed slope on gravity current statistics.
- To explore interfacial turbulence dynamics in subcritical, supercritical, and a newly identified transcritical regime.
- To elucidate the mechanisms behind the cyclic evolution of interfacial instabilities.
Main Methods:
- Direct numerical simulations (DNS) with high resolution (nearly 1 billion degrees of freedom).
- Analysis of flow statistics and turbulence dynamics across varying bed slopes.
- Identification and characterization of interfacial instabilities.
Main Results:
- Bed slope significantly influences gravity current flow statistics.
- Distinct subcritical and supercritical turbulence regimes were observed.
- A transcritical regime characterized by intermittent cascading interfacial instabilities was identified.
- Instability cycles are linked to departures from a self-sustaining equilibrium state.
Conclusions:
- Bed slope is a critical parameter controlling gravity current behavior.
- The newly identified transcritical regime offers new insights into flow dynamics.
- Non-equilibrium dynamics drive cyclic interfacial instabilities in gravity currents.
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