Capturing the wall turbulence in CFD simulation of human respiratory tract

Abstract

The present study is concentrated on simulating the turbulent airflow in human respiratory tract using computational fluid dynamics (CFD). Attention is emphasized on local Reynolds number in terms of y+ (y-plus) value for the near wall mesh refinement using a finite volume method (FVM) based CFD solver to capture wall turbulence parameters. Turbulence in human respiratory tract is formed at high breathing conditions, typically during the running or exercise. The turbulence formation in human respiratory tract also occurs due to its irregular cross-sections and curved surfaces of the respiratory walls. CT scan based realistic respiratory model is considered for the study. Two turbulence models, namely realizable k–ε and low Reynolds number k –ω models are used in the study to capture turbulent flow phenomena for inspiratory flow condition at 60 liter/minute. During turbulent flow, large velocity gradient occurs near the respiratory wall and hence correct y+ value is essential for accurate prediction of wall bounded flow using these turbulence models. The outcome of the paper is based on the judicious selection of y+ value and the turbulence models, which are found vital to correctly simulate airflow in respiratory tract at heavy-breathing conditions.