Lagrangian Coherent Structures in Coastal Waters: Sensitivities to Interpolation Schemes, and Mesh Resolution

Ghosh, Anusmriti; Suara, Kabir Adewale; Brown, Richard J.

doi:10.3850/38wc092019-0729

Cited by 2 publications

(2 citation statements)

References 11 publications

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“…Linear interpolation is used for the spatial and temporal interpolation of velocity to the location of the particles in the advection scheme. There is no qualitative difference in the output for the different interpolation scheme as shown in [11].…”

Section: Discussionmentioning

confidence: 98%

Identifying material repelling areas in coastal water systems through Lagrangian coherent structures

Ghosh¹,

Suara²,

Brown³

2020

Australasian Fluid Mechanics Conference (AFMC)

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Lagrangian coherent Structures (LCS) are useful to investigate material transport and have only recently been applied to coastal waters. Identification of material lines by LCS in a chaotic flow can assist in highlighting areas of strong spreading of floating materials in waterways. Here we investigate the persistent areas of potential strong spreading of floating materials in a semi-enclosed tidal embayment using LCS. The analysis is performed on the output of a hydrodynamic model of Moreton Bay, a semi-enclosed subtropical embayment on the east coast of Australia. The forward finite time Lyapunov exponent (FTLE) is used as diagnostic for repelling material lines which signals areas of strong spreading. The work presents the tidal asymmetry results for the investigation of strong repelling of floating pollution and contaminants. The results indicate that in the spring and ebb tides, persistence of repelling material is more prominent than neap and flood tides.

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Section: Discussionmentioning

confidence: 98%

Identifying material repelling areas in coastal water systems through Lagrangian coherent structures

Ghosh¹,

Suara²,

Brown³

2020

Australasian Fluid Mechanics Conference (AFMC)

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“…The optimum interpolation technique is identified from the four interpolation schemes (linear, cubic, biharmonic and natural). The linear interpolation method works by interpolating in each respective dimension [51,52]. This interpolation method depends on the specific triangulation of the data points [53].…”

Section: Interpolation Schemementioning

confidence: 99%

Sensitivity and robustness of Lagrangian coherent structures in coastal water systems

et al. 2021

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In coastal water systems, horizontal chaotic dispersion plays a significant role in the distribution and fate of pollutants. Lagrangian Coherent Structures (LCSs) provide useful tools to approach the problem of the transport of pollutants and have only recently been applied to coastal waters. While the fundamentals of the LCS approach using idealised analytical flow fields are well established in the literature, there are limited studies on their practical implementations in coastal waters where effects of boundaries and bathymetry frequently become significant. Due to their complex bathymetry and boundaries, unstructured grid systems are commonly used in modelling of coastal waters. For convenient derivation of LCS diagnostics, structured grids are commonly used.Here we examine the effect of mesh resolution, interpolation schemes and additive random noise on the LCS diagnostics in relation to coastal waters. Two kinematic model flows, the double gyre and the meandering jet, as well as validated outputs of a hydrodynamic model of Moreton Bay, Australia, on unstructured grids are used.The results show that LCSs are quite robust to the errors from interpolation schemes used in the data conversion from unstructured to structured grid. Attributed to the divergence in the underlying flow field, the results show that random errors in the order of 1-10 % cause a break down in the continuity of ridges of maximum finite time Lyapunov exponents and closed orbit elliptic LCSs. The result has significant implications on the suitability of applying LCS formulations based on a deterministic flow field to diffusive coastal waters. Highlights• The work examines the sensitivities of applying Lagrangian coherent structures (LCSs) diagnostics for coastal waters with complex boundaries. • LCSs are robust to the errors from interpolation schemes used for unstructured to structured grid velocity data conversion. • Additive random errors in the order of 1-10 % cause a break down in the continuity of ridges of maximum finite time Lyapunov exponents and closed orbit elliptic LCSs.

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Lagrangian Coherent Structures in Coastal Waters: Sensitivities to Interpolation Schemes, and Mesh Resolution

Cited by 2 publications

References 11 publications

Identifying material repelling areas in coastal water systems through Lagrangian coherent structures

Identifying material repelling areas in coastal water systems through Lagrangian coherent structures

Sensitivity and robustness of Lagrangian coherent structures in coastal water systems

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