Calculating Particle-to-wall Distances in Unstructured Computational ¯uid Dynamic Models

Knowledge of particle deposition is relevant in biomedical engineering situations such as computational modeling of aerosols in the lungs and blood particles in diseased arteries. To determine particle deposition distributions, one must track particles through the ¯ow ®eld, and compute each particle's distance to the wall as it approaches the geometric surface. For complex geometries, unstructured tetrahedral grids are a powerful tool for discretizing the model, but they complicate the particle-to-wall distance calculation, especially when non-linear mesh elements are used. In this paper, a general algorithm for ®nding minimum particle-to-wall distances in complex geometries constructed from unstructured tetrahedral grids will be presented. The algorithm is validated with a three-dimensional 90° bend geometry, and a comparison in accuracy is made between the use of linear and quadratic tetrahedral elements to calculate the minimum particle-to-wall distance.