Deleuze (2025) Nonlinear internal gravity wave modes and settling particles in stratified fluids : two pathways to mixing

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: theses.fr (ABES)
• Year: 2025
• Date: 2025-09-12
• Authors: Julie Deleuze
• DOI: None

Research Groups

[Information not provided in the paper text.]

Short Summary

This study experimentally investigates energy transfer and diapycnal mixing in stratified fluids, focusing on internal gravity waves and particle sedimentation. It reveals complex non-linear wave dynamics, including resonant triadic instability and a feedback loop between wave evolution and background stratification, alongside quantifying mixing induced by sedimenting particle clouds.

Objective

• To understand the energy cascade towards small scales in stratified fluids, crucial for parameterizing diapycnal mixing in global climate models.
• To observe and characterize resonant triadic instability in internal gravity waves, analyzing the combined constraints of non-linear and geometric resonance.
• To investigate the feedback loop between non-linear internal wave dynamics and background stratification evolution, identifying different mixing regimes and the nature of instabilities leading to wave breaking.
• To quantify irreversible energy transfer and mixing induced by the sedimentation of particle clouds in a stratified fluid.

Study Configuration

• Spatial Scale: Laboratory scale (rectangular domain).
• Temporal Scale: Transient and evolving processes, including slow evolution of background stratification and fluid return to rest after perturbation.

Methodology and Data

• Models used: No computational models were explicitly used; the study is experimental.
• Data sources: Laboratory experiments involving generation of internal waves in a rectangular domain, varying wave characteristics and domain geometry, intense forcing, and simultaneous measurements of velocity and density fields. Experiments also included observing sedimentation of particle clouds.

Main Results

• Characteristics of secondary waves generated by resonant triadic instability are strongly constrained by both non-linear resonance conditions and the geometric resonance of the experimental domain.
• The interaction of these constraints leads to complex non-linear dynamics, including the generation of internal waves that deviate from their dispersion relation.
• Under intense forcing, a slow evolution of the background stratification was observed, which modifies the spatial structure of internal waves, establishing a feedback loop between non-linear dynamics and mixing.
• Several mixing regimes associated with different efficiencies were identified, and localized mixing events were detected, with the nature of instabilities causing wave breaking being studied.
• Sedimentation of particle clouds in a stratified fluid induces mixing by entraining light fluid into the wake, with mixing occurring only in specific regimes.
• Irreversible energy transfer from the sedimenting particles to the surrounding fluid was quantified.

Contributions

• Provides novel experimental insights into the complex interplay of non-linear and geometric resonance in internal wave dynamics within stratified fluids.
• Demonstrates and characterizes a crucial feedback loop between internal wave dynamics and the evolution of background stratification, identifying distinct mixing regimes.
• Offers detailed observations of localized mixing events and the underlying instabilities responsible for wave breaking, enhancing understanding of small-scale energy dissipation.
• Quantifies irreversible energy transfer and mixing efficiency due to particle sedimentation, expanding the scope of mixing mechanisms studied beyond wave-induced processes.
• Contributes to improving the parameterization of diapycnal mixing in global climate models by elucidating fundamental energy transfer mechanisms.

Funding

[Information not provided in the paper text.]

Citation

@article{Deleuze2025Nonlinear,
  author = {Deleuze, Julie},
  title = {Nonlinear internal gravity wave modes and settling particles in stratified fluids : two pathways to mixing},
  journal = {theses.fr (ABES)},
  year = {2025},
  url = {https://openalex.org/W4416042367}
}