Examining mesh independence for flow dynamics in the human nasal cavity

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Scripts used in the paper with the velocity profile data on planes.

Increased computational resources provide new opportunities to explore sophisticated respiratory modelling. A survey of recent publications showed a steady increase in the number of mesh elements used in computational models, with time. Complex geometries such as the nasal cavity exhibit sharp gradients, and irregular curvatures, leading to abnormal flow development occurring across its surface. This requires a robust method for examining the near wall mesh resolution. The non-dimensional wall unit y^+ (often used in turbulent flows) was used as a parameter to evaluate the near wall mesh in laminar flows.

Mesh independence analysis from line profiles showed that the line location had a significant influence on the result. Furthermore, using a single line profile as a measure for mesh convergence was unsuitable for representing the entire flow field. To improve this, we proposed a 2D cross-sectional plane subtraction method where scalar values (such as the velocity magnitude) on a cross-sectional plane were interpolated onto a regularly spaced grid. The new interpolated grid values, from any two meshed models, could then be compared for changes caused by the different meshed models. Its application to 3D volume subtraction was also demonstrated.
The results showed that if the near wall mesh was sufficiently refined, then narrowed passages were less reliant on the overall mesh size. However, in wider passages velocity magnitudes were sensitive to mesh size and this required a more refined mesh.

Keywords: mesh independence, nasal cavity, y^+, y-plus, laminar flow


2D plane subtraction results

3D subtraction results


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