Time resolved analysis of steady and oscillating flow in the upper human airways

Große, S.; Schröder, Wolfgang; Klaas, Michael; Klöckner, Andreas; Roggenkamp, Jan

doi:10.1007/s00348-007-0318-y

Cited by 53 publications

(66 citation statements)

References 15 publications

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“…The technique has already been successfully applied to perform measurements of the flow field evolving in a realistic, transparent-but rigid-silicone model of the upper human airways (Große et al 2007(Große et al , 2008.…”

Section: Introductionmentioning

confidence: 99%

A refractive index-matched facility for fluid–structure interaction studies of pulsatile and oscillating flow in elastic vessels of adjustable compliance

et al. 2009

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The flow field in the respiratory and vascular system is known to be influenced by the flexibility of the walls. However, up to now, most of the experimental biofluidic investigations have been performed in rigid models due to the complexity and necessity of optical access. In this paper, a facility and measurement techniques for studying oscillating and pulsatile flow in elastic vessels will be described. The investigated vessel models have been adapted such that fluid-mechanical and structure-mechanical characteristics represent realistic blood flows in medium blood vessels. That is, characteristic parameters, i.e., the Reynolds and Womersley number, as well as mechanical properties of the flexible wall, i.e., the Young's modulus and the material compliance, have been chosen to reasonably represent realistic flow conditions. First, a method to manufacture elastic models, which mimic the structure-mechanical properties of vascular vessels is described. The models possess a tunable compliance and are made of transparent polydimethylsiloxane. Second, the experimental setup of the flow facility will be elucidated. The flow facility allows to mimic pulsatile flow at physiologically relevant Reynolds and Womersley numbers. The precise form of the flow cycle can individually be controlled. Water/glycerine is used as flow medium for refractive index matching particle image velocimetry (PIV) measurements. The PIV recordings not only allow to assess the mean cross-sectional flow field but also further enable to simultaneously detect the movement of the flexible wall. Additionally, the local wall-shear stress can be obtained from the single-pixel line resolved near-wall flow field. To confirm the flow conditions of the oscillatory laminar flow inside the flow facility and to evaluate the ability to assess the flow field, measurements in a straight, uniform diameter, rigid Plexiglas pipe under identical conditions to those of the oscillating flow in the flexible vessel have been performed. The measurements of oscillating flow in the rigid pipe corroborate the experimentally obtained flow field and the wall-shear stress to well confirm Womersley's analytical solution and thereby evidence the quality of the flow facility and of the measurement techniques. To further study the detectability of the vessel deformation, oscillating flow at Reynolds numbers based on the non-dilated vessel diameter D and peak velocities Re D ranging from 1,000 to 1,750 and at Womersley numbers a ranging from 5 to 17.5 has been investigated in an elastic vessel.

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Section: Introductionmentioning

confidence: 99%

A refractive index-matched facility for fluid–structure interaction studies of pulsatile and oscillating flow in elastic vessels of adjustable compliance

et al. 2009

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“…A Dirichlet condition, i.e., the velocity distribution, has been imposed at the tracheal cross section at inspiration and expiration. To validate the numerical solutions, the results are compared with experimental data obtained by Particle Imaging Velocimetry (PIV) measurements, which have been performed using a silicon model of the same lung geometry [3]. The results are investigated at a reference plane the location of which is indicated in Fig.…”

Section: Steady Flow Fieldmentioning

confidence: 99%

“…Since the numerical method is capable of reproducing small-scale features of lung flow, the results serve to fundamentally understand respiratory mechanisms. Thus, the numerical results allow an extended analysis of the three-dimensional flow structures observed in [3].…”

Section: Introductionmentioning

confidence: 99%

“…The understanding of the flow processes in the upper human airways is of great importance in developing aerosol drug delivery systems and to improve the efficiency and usability of artificial respiration. Numerous experimental and numerical investigations of lung flow have been conducted so far [1][2][3][4][5]. However, due to the high geometric intricacy of the human lung, there is still a considerable amount of uncertainty concerning the very complex flow field and results for realistic lung models are still rare.…”

Section: Introductionmentioning

confidence: 99%

“…The geometry covers the trachea and the bronchial tree down to the sixth generation. A silicon model of the same geometry has been experimentally investigated in [3]. The flow field is simulated via the Lattice-Boltzmann method (LBM) [12].…”

Section: Introductionmentioning

confidence: 99%

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Numerical investigation of the flow field in the upper human airways

Eitel

o}der

Meinke

2009

Modelling in Medicine and Biology VIII

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The flow in a realistic model of the human lung is numerically simulated at steady and unsteady inspiration and expiration. A model of a human lung ranging from the trachea down to the sixth generation of the bronchial tree is used for the simulation. The numerical analysis is based on the Lattice-Boltzmann method, which is particularly suited for flows in extremely intricate geometries such as the upper human airways.The results for steady air flow at inspiration and expiration for a diameter based Reynolds number of Re D = 1250 evidence secondary vortex structures and air exchange mechanisms. It is shown that the asymmetric geometry of the human lung plays a significant role for the development of the flow field in the respiratory system. Secondary vortex structures observed in former studies are reproduced and described in detail.The solutions for unsteady respiration allow a detailed analysis of the temporal formation of secondary flow structures whereas the time dependence is much more pronounced at inspiration than at expiration.

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3D phase contrast MRI in models of human airways: Validation of computational fluid dynamics simulations of steady inspiratory flow

Collier

Kim

Chung

et al. 2018

Magnetic Resonance Imaging

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Time resolved analysis of steady and oscillating flow in the upper human airways

Cited by 53 publications

References 15 publications

A refractive index-matched facility for fluid–structure interaction studies of pulsatile and oscillating flow in elastic vessels of adjustable compliance

A refractive index-matched facility for fluid–structure interaction studies of pulsatile and oscillating flow in elastic vessels of adjustable compliance

Numerical investigation of the flow field in the upper human airways

3D phase contrast MRI in models of human airways: Validation of computational fluid dynamics simulations of steady inspiratory flow

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