Interaction between a simplified soft palate and compressible viscous flow

Abstract

Fluid-structure interaction in a simplified 2D model of the upper airways is simulated to study flow-induced oscillation of the soft palate in the pharynx. The goal of our research has been a better understanding of the mechanisms of the Obstructive Sleep Apnea Syndrome and snoring by taking into account compressible viscous flow. The inspiratory airflow is described by the 2D compressible Navier-Stokes equations, and the soft palate is modeled as a flexible plate by the linearized EulerBernoulli thin beam theory. Fluid-structure interaction is handled by the arbitrary LagrangianEulerian formulation. The fluid flow is computed by utilizing 4 th order accurate summation by parts difference operators and the 4 th order accurate classical Runge-Kutta method which lead to very accurate simulation results. The motion of the cantilevered plate is solved numerically by employing the Newmark time integration method. The numerical schemes for the structure are verified by comparing the computed frequencies of plate oscillation with the associated second mode eigenfrequency in vacuum. Vortex dynamics is assessed for the coupled fluid-structure system when both airways are open and when one airway is closed. The effect of mass ratio, rigidity and damping coefficient of the plate on the oscillatory behaviour is investigated. An acoustic analysis is carried out to characterize the acoustic wave propagation induced by the plate oscillation. It is observed that the acoustic wave corresponding to the quarter wave mode along the length of the duct is the dominant frequency. However, the frequency of the plate oscillation is recognizable in the acoustic pressure when reducing the amplitude of the quarter wave mode.

High‐order ghost‐point immersed boundary method for viscous compressible flows based on summation‐by‐parts operators

“…Among those, obstructive sleep apnea (OSA) and snoring are closely related to the flow conditions in the upper airways. Obstructive sleep apnea syndrome (OSAS) is one of the most prevalent types of sleep disorders caused by repetitive collapse of the soft tissues in the upper airways …”

“…The present method is now applied to the real geometry of the human upper airway to demonstrate its capability for dealing with complex geometries in practical applications. Disorders of the upper airways are often associated with 56 In this study, a medical image (cf Figure 18A) was provided by the Department of Radiology and Nuclear Medicine at St. Olavs Hospital, the university hospital in Trondheim, Norway. The computed tomography (CT) image is for patient number 12 in the study by Moxness and Nordgård, 57 a 67-year-old man who showed great improvement in apnea hypopnea index after a septum plastic surgery in the nasal cavity such that he is no longer diagnosed with OSAS.…”

Computational fluid dynamics modelling of human upper airway: A review

“…7 [64] . The soft palate was assumed to be a flexible plate in the computational model, which separated the nasal and oral inlets.…”

“…7. Simplification of model on the possibility of preventing complicated meshing or grid generation process through a 2D-computational domain of a human upper airway [64] . try (in rectangular) of the upper airways ( Fig.…”

“…try (in rectangular) of the upper airways ( Fig. 11 ) [64] . The curved region in Sections 3 and 4 represent the soft tissue or palate.…”