Computational modelling of nasal respiratory flow

CFD has emerged as a promising diagnostic tool for clinical trials, with tremendous potential. However, for real clinical applications to be useful, overall statistical findings from large population samples (e.g., multiple cases and models) are needed. Fully resolved solutions are not a priority, but rather rapid solutions with fast turn-around times are desired. This leads to the issue of what are the minimum modelling criteria for achieving adequate accuracy in respiratory flows for large-scale clinical applications, with a view to rapid turnaround times. This study simulated a highly-resolved solution using the large eddy simulation (LES) method as a reference case for comparison with lower resolution models that included larger time steps and no turbulence modelling. Differences in solutions were quantified by pressure loss, flow resistance, unsteadiness, turbulence intensity, and hysteresis effects from multiple cycles. The results demonstrated that sufficient accuracy could be achieved with lower resolution models if the mean flow was considered. Furthermore, to achieve an established transient result unaffected by the initial start-up quiescent effects, the results need to be taken from at least the second respiration cycle. It was also found that the exhalation phase exhibited strong turbulence. The results are expected to provide guidance for future modelling efforts for clinical and engineering applications requiring large numbers of cases using simplified modelling approaches.

Automated summary

CFD has shown great potential as a diagnostic tool in clinical trials, but overall statistical findings from large population samples are necessary for real clinical applications. This study compared a highly-resolved solution with lower resolution models to determine minimum modelling criteria for accurate respiratory flows in large-scale clinical applications. Results indicated that lower resolution models could achieve sufficient accuracy if mean flow was considered, and a stable transient result required data at least from the second respiration cycle. The study's findings offer guidance for future modelling efforts in clinical and engineering applications.