Direct numerical simulations of flow in realistic mouth–throat geometries

Abstract

The flow in a set of four realistic mouth-throat geometries at a flow rate of 30 L/min is stud-

Effect of the velopharynx on intraluminal pressures in reconstructed pharynges derived from individuals with and without sleep apnea

“…However, these values were meaningful for the measurement conditions (awake subjects breathing normally via the nose) and when considering that only a portion of the pharynges was reconstructed (Fitzpatrick et al, 2003). Moreover, the values of maximum velocity magnitude U max , in the range 3.7-4.9 m.s −1 , aligned well with those reported in other computational studies on quiet breathing with both anatomically-correct (Mihaescu et al, 2008;Nicolaou and Zaki, 2013) and idealized (Cui and Gutheil, 2011) airway geometries.…”

“…where CSP VP denotes the perimeter of the cross-section of minimum area in the velopharynx and ν the kinematic viscosity of air (1.52×10 −5 m 2 .s −1 ), corresponded to that observed during quiet breathing (Van Hirtum et al, 2007;Nicolaou and Zaki, 2013). The total pharyngeal resistance: gave values in the range 0.18-0.48 cmH2O.s.l −1 , which appeared to be low compared to most values reported in the literature (Herman, 2008;White et al, 1985;Tamisier et al, 2000).…”

“…Flow simulations are thought to yield a stronger indicator of propensity to OSA than anatomical features because of the nonlinear relationship between geometric and flow characteristics within the pharynx (Nicolaou and Zaki, 2013). The main focus of the present study was therefore to determine the influence of velopharyngeal shape and size on the pressure drop across the pharynx and to evaluate the capacity of flow characteristics to identify individuals with and without OSA.…”

“…Direct numerical simulations (DNS) have revealed the very different flow patterns which can appear within the airway due to the complexity of the airway shape and the inter-subject variability (Nicolaou and Zaki, 2013). However, the use of largeeddy simulation (LES) or steady Reynolds-averaged NavierStokes (RANS) turbulence models can reduce the computational cost to simulate the flow within the airway and give accurate predictions of important flow features (Mihaescu et al, 2008;Cui and Gutheil, 2011).…”

A robust direct-forcing immersed boundary method with enhanced stability for moving body problems in curvilinear coordinates

“…Curvilinear IB methods are particularly useful in bioflow problems which often involve complex geometries, e.g. flow in a mechanical heart valve [34] or flow in the respiratory airways [35]. A curvilinear grid can improve efficiency by minimising the number of grid points outside the fluid domain, can have a more natural alignment with the streamlines which is desirable for the accuracy of the solution, and might provide a better wall-normal resolution than a Cartesian grid.…”