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A critical comparison of Lagrangian methods for coherent structure detection
Alireza Hadjighasem1, Mohammad Farazmand1, Daniel Blazevski2
1Department of Mechanical Engineering, MIT, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, USA.
Chaos (Woodbury, N.Y.)
|June 4, 2017
Summary
Detecting coherent structures in fluid flows is challenging. This study compares twelve methods, finding significant discrepancies and recommending self-consistency checks for Lagrangian coherence detection techniques.
Area of Science:
- Fluid Dynamics
- Geophysics
- Applied Mathematics
Background:
- Accurate identification of coherent structures is crucial for understanding complex fluid flows.
- Existing methods for detecting these structures often yield inconsistent results.
- Temporally aperiodic and two-dimensional flows present unique challenges for structure detection.
Purpose of the Study:
- To systematically review and compare twelve distinct methods for detecting finite-time coherent material structures.
- To evaluate the performance of mathematical approaches and diagnostic scalar fields on benchmark flow cases.
- To identify limitations and provide recommendations for robust Lagrangian coherence detection.
Main Methods:
- Comparison of twelve detection techniques, including mathematical methods and diagnostic scalar fields.
- Application and evaluation on three benchmark datasets: Bickley jet, 2D turbulence, and Jovian wind fields.
- Passive advection analysis to assess the validity of detected coherent structures.
Main Results:
- Significant variations in coherent structure predictions among different methods were observed.
- False positives and negatives were identified, even in mathematically justified approaches.
- Method performance varied depending on the specific flow configuration and its characteristics.
Conclusions:
- No single method universally excels in detecting coherent structures across all flow types.
- Mathematical rigor alone does not guarantee accurate detection; flow-specific validation is essential.
- Establishing minimal self-consistency requirements is vital for reliable Lagrangian coherence detection.
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