On assessing the quality of particle tracking through computational fluid dynamic models

Area of Science:

• Computational fluid dynamics (CFD)
• Biomedical engineering
• Fluid mechanics

Background:

• Accurate quantification of particle deposition, transit times, and shear exposure is vital for CFD studies of respiratory and arterial systems.
• Lagrangian approaches are necessary for tracking particles but require sufficiently resolved velocity fields, which are difficult to ascertain beforehand.

Purpose of the Study:

• To introduce and validate Volumetric Residence Time (VRT) as a metric for quantifying mesh resolution in 3D CFD models.
• To assess Lagrangian mass conservation and guide mesh refinement for accurate path-dependent quantity extraction.

Main Methods:

• Extended Volumetric Residence Time (VRT) from 2D to 3D models for assessing Lagrangian fluid element (LFE) uniformity.
• Computed VRT and particle deposition in 3D steady flow models of a stenosed carotid bifurcation using varying finite element meshes.
• Analyzed LFE distribution to evaluate mesh adequacy for Lagrangian particle tracking.

Main Results:

• Uniform VRT, indicative of Lagrangian mass conservation, was not achieved even with highly resolved meshes and dense LFE seeding.
• VRT maps effectively identified under-resolved regions within the computational mesh.
• The study demonstrated the utility of VRT for guiding mesh refinement in CFD models.

Conclusions:

• Care must be taken when extracting path-dependent quantitative information from CFD simulations due to potential under-resolution.
• VRT serves as a valuable tool for evaluating and improving mesh quality for Lagrangian particle tracking in complex physiological flows.