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Updated: Jun 14, 2026
10:53
Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques
Published on: March 12, 2019
Sensitivity of Lagrangian coherent structure identification to flow field resolution and random errors
Ali B Olcay1, Tait S Pottebaum, Paul S Krueger
1Department of General Engineering, University of Wisconsin, Platteville, 1 University Plaza, Platteville, Wisconsin 53818, USA.
Chaos (Woodbury, N.Y.)
|April 8, 2010
Summary
Random errors and reduced resolution significantly impact Lagrangian coherent structures (LCSs) identification. Even low noise levels can distort LCSs, affecting flow analysis accuracy.
Area of Science:
- Fluid dynamics
- Computational fluid dynamics
- Flow visualization
Background:
- Lagrangian coherent structures (LCSs) are crucial for understanding fluid transport.
- Eulerian velocity fields are commonly used to identify LCSs.
- Flow measurement techniques can introduce spatial, temporal, and random errors.
Purpose of the Study:
- To evaluate the impact of spatial/temporal resolution and random errors on LCS identification.
- To assess the accuracy of LCSs derived from degraded Eulerian velocity fields.
- To understand how common flow measurement errors affect LCS analysis.
Main Methods:
- Canonical flows (2D vortex pair, vortex ring) were used.
- Flow fields were degraded by smoothing, coarser grids, random noise, and time subsampling.
- Degradation methods mimicked digital particle image velocimetry (DPIV) errors.
- Identified LCSs were compared to true LCSs from analytical or high-fidelity simulations.
Main Results:
- Noise levels of 5%-10% caused significant random deviations in LCS (separatrix) location.
- Mean LCS location remained relatively accurate despite noise.
- Spatial and temporal resolution degradations primarily affected transient flow regions with strong gradients.
- Deviations were observed even with high spatial resolution (2% of jet diameter).
Conclusions:
- Flow measurement errors significantly impact LCS accuracy.
- Careful consideration of resolution and noise is vital for reliable LCS identification.
- The study provides insights into the robustness of LCS analysis under realistic measurement conditions.
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