Experimental simulation trial for human lung's flow mechanism ARA - - PowerPoint PPT Presentation

ヒトの肺の流れの力学解明に向けた実験的シミュレーション

Experimental simulation trial for human lung's flow mechanism

2016/6/10

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Hi Hiroyu

• yuki

ki HI HIRAH AHAR ARA 平原裕行 Division of Human Support and Production Science 人間支援・生産科学部門 Saitama University 埼玉大学

Get ‘REAL SOLUTION’ ? Or Get ‘ESSENCE’?

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Conventional Way

EFD CFD V & V

Promoting Way

EFD CFD Check and Review For Inovation

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Today’s presentation 1) Irreversible Laminar Flow in Peripheral Lungs 2) Coanda effect simulation

What we should remove from complex factor ?

Potential ? or Viscous ? Complete viscous (laminar) ! But, something happen.

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223 bifurcations makes intricate structure

Fig.2 Delivery of Oxygen and Carbon Dioxide In the Respiratory System

Oxygen-rich air from environment Nasal cavities Pharynx Trachea Bronchi Bronchioles Alveoli Oxygen and carbon dioxide exchange at alveoli Bronchioles Bronchi Trachea Pharynx Nasal cavities Carbon dioxide-rich air to the environment

Fig.1 Macroscopic view of a plastic cast of the airways (yellow) the pulmonary arteries (red) and veins (blue) of a human lung. (Anatomy Institute of Anatomy, University of Berne, Switzerland)

High-frequency oscillatory ventilation: Mechanisms of gas exchange and lung mechanics

• J. Jane Pillow, MBBS, FRACP, PhD

Crit Care Med 2005 Vol. 33, No. 3 (Suppl.)

CHANG, H. K. Mechanisms of gas transport during ventilation by high frequency

• scillation.
• J. Appl. Physiol.: Respirat. Environ. Exercise Physiol.

56( 3): 553-563, 1984.- 5 flow modes by Chang(1984) Ventilation by high-frequency oscillation (HFO) presents some difficulties in understanding exactly how gas is transported in the lung. However, at a qualitative level, five modes of transport may be identified: 1 ) direct alveolar ventilation in the lung units situated near the airway opening; 2) bulk result of recirculation of convective mixing air among units of in the conducting airways as a inhomogeneousti me constants; 3) convective transport of gases-as a result of the asymmetry between inspiratory and expiratory velocity profiles; 4) longitudinal dispersion caused by the interaction between axial velocities and radial transports due to turbulent eddies and/or secondary swirling motions 5) molecular diffusion near the alveolocapillary membrane. These modes of transport are not mutually exclusive and certainly

• interact. It is therefore difficult to

make quantitative predictions about the overall rate of transport. Qualitatively, it may now be stated with confidence that convective transport in the tracheobronchial tree is very important during HFO as in normal breathing and . that increasing tidal volu .me is more effective than increa sing frequency in improving gas exchange during HFO. To optimi .ze the gas transport efficiency of HFO, future research should focus on identifying the rate-li .miting mode of transport for a given set of geometric and dynamic conditions.

• FIG. 9. Modes of gas transport during

high-frequency oscillation (HFO) and tentative sketch of their zones of dominance. These modes of transport are not mutually exclusive and may interact to achieve

• bserved efficiency in animal or

patient studies.

General

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Fig.20 Velocity distribution in the bifurcation plane and two cross sections at 7th generation: (A) end inspiration, (B) end expiration. Blue, negative axial velocity to the left; Red, positive axial velocity to the right. (Choi et al. 2010) Fig.19 Illustration of Pendelluft mechanism (H. Hirahara)

Pendelluft Flow Coaxial Flow Taylor Dispersion Flow

• 3. GAS FLOW IN BRONCHIOLES INDUCED BY

HFOV

3.1 Introduction of HFOV

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What parameters should be considered ?

Fig.3 Flow regimes of the conducting airway categorized on the basis of a dimensionless frequency α2 (where α is the Womersley number) and a dimensionless stroke length L/a. Jan et al. Fig.4 Re, Pe, and Wo numbers for TV=150mL at each generation. (Hirahara, 2010, J of Fluid and Science Technology)

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Reynolds number is not only similarity parameter, But also momentum diffusion speed !

𝑆𝑓 = 𝑉𝑀 𝜉 = 𝑉 𝜉/𝑀 = Convective speed Momentum Diffusion speed 𝑄𝑓 = 𝑉𝑀 𝛽 = 𝑉 𝛽/𝑀 = Convective speed Molecular Diffusion speed

Peclet number is also important,

𝜉: viscousity 𝛽: 𝑛olacular diffusion coefficient

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Fig.5 Bifurcating structure of human lung based on Weibel’s model

• 1. The Weibel’s lung model is symmetric and relatively

simple, it helps to diminish the disturbance of over-complex structure, to get more general and representative gas flow phenomena.

• 2. The weibel’s lung model facilitates not only numerical

simulation but also PIV experiment.

Why we will not use CT data ?

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Why the bronchioles is target ? (below G18)

• 1. Almost all researchers focus on upper-airway flow

above G10. What happens at the distal region?

• 2. HFOV adopts fast and shallow oscillatory ventilation,

the small tidal volume cannot reach the respiratory zone at each oscillation. How can HFOV be effective in ventilation? How can fresh gas reach the distal region?

• nly by molecular diffusion? Or by some progressive

delivery?

Fig.6 Illustration of main research region and reachable area of single tidal volume of HFOV

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What happens in High frequency respiration ?

Conventional Ventilation Or Normal Breathing High Frequency Oscillatory Ventilation Super-High Frequency Oscillatory Ventilation About 0.2Hz About 10Hz 100Hz… f About 500ml About 50ml 5ml 10ml… TV

f × TV VT (constant) =

Basic principle:

Normal  HVOV  Super-HFOV

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Numerical modeling

Dimensions of mother to grand-daughter tubes from G18 to G20 (left) and volume mesh (right) Inlet Outlets

Governing Equations Boundary conditions for inlet Boundary conditions for outlets Boundary conditions for peripheral wall Rigid wall with non-slip condition

Fundamental condition of CFD without molecular diffusion without turbulent model

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Fig.9 Setting for VOF calculation by 2 fluids (Molecular diffusion neglected) Fig.10 Setting for VOF calculation with 4 fluids (Molecular diffusion neglected) Fig.8 Lagrangian particles setting at different locations

Gas exchange in ‘Normal Breath’ at different position

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Fig.11 Particle fluctuations in G18-G20 by CV (sinusoidal, 0.2Hz, 500mL) in 5 seconds

Gas exchange in ‘Normal Breath’ at different position

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Gas exchange in ‘Normal Breath’ at different position

VOF calculation for Normal Breath (sinusoidal, 0.2Hz, 500mL) in 5 seconds

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5 seconds later

Gas exchange in ‘Normal Breath’

Gas redistribution due to large TV

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Fig.23 Setting for VOF calculation with 2 fluids (Molecular diffusion neglected) Fig.24 Setting for VOF calculation with 4 fluids (Molecular diffusion neglected) Fig.22 Lagrangian particles at the same locations of VOF interfaces in Fig.12

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Fig.25 Particle fluctuations in G18-G20 by HFOV (sinusoidal, 10Hz, 50mL) in 5 seconds

GAS FLOW IN BRONCHIOLES INDUCED BY HFOV

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Redistribution of massless particles caused by raking effect in G18 with HFOV(Sinusoidal, 10Hz, 50ml) in 3 cycles (0.3seconds)

3-D View of Lagrangian tracking

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Fig.26 VOF calculation for HFOV (10Hz, 50mL, sinusoidal) in 5 seconds

GAS FLOW IN BRONCHIOLES INDUCED BY HFOV

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Fig.27 VOF calculation for HFOV (10Hz, 50mL, sinusoidal) in 5 seconds 0 second 0.3 seconds 1 second 5 seconds

GAS FLOW IN BRONCHIOLES INDUCED BY HFOV

Fig.28 Comparison of gas rearrangement in G18-G20 with CV (sinusoidal, 0.2Hz, 500mL) and HFOV (sinusoidal, 10Hz, 50mL) in 5 seconds

VS VS

Normal HFOV

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HFOV rakes the gas near the central-axis downwards and the peripheral gas upwards much more than CV does, which is named raking effect here, it features similar effect of the coaxial counter-flow. A significant difference between raking effect and counter-flow is that raking effect doesn’t apparently involve flows in two opposite directions

• simultaneously. Raking effect can be seen due to irreversibility as a time-

average effect in laminar flow within a tiny space where viscous force is dominant.

Conclusion 1 Conclusion 2

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PIV experiment in Real Scale !

Micro-PIV(Particle Image velocimetry) Measurement

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No obvious coaxial counter-flow as same as CFD

Fig.48 Experiment result of velocity vectors in one cycle with small lung model and HFOV (Sinusoidal, 10Hz, 50ml) 1.When inhaling velocity maximizes. 2.When exhaling velocity maximizes. 3.End of inhalation. 4.End of exhalation.

1 4 3 2

Phase locked ensemble averaged profiles

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Fig.49 Experiment result of particle tracks in one cycle with small lung model and HFOV (Sinusoidal, 50ml, 10Hz(1) /20Hz (2))

(1) (2)

Lagrangian tracking shows the ‘raking effect’

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6 modes of transport in HFOV

• 1. Direct ventilation
• 2. Mixing by Pendelluft or out-of-phase oscillation
• 3. Convective dispersion due asymmetry between

inspiratory and expiratory velocity profile

• 4. Longitudinal dispersion due to turbulent eddies

and/or secondary swirling motions

• 5. Molecular diffusion
• 6. Raking effect (distal region)

6th mode is important in distal region

5 modes of transport in HFOV

• 1. Direct ventilation
• 2. Mixing by Pendelluft or out-of-phase oscillation
• 3. Convective dispersion due asymmetry between

inspiratory and expiratory velocity profile

• 4. Longitudinal dispersion due to turbulent eddies

and/or secondary swirling motions

• 5. Molecular diffusion

Fig.52 Comparison of raking effect with different gas viscosity (1.983×10-5 Pa·S for the left, 1.983×10-3 Pa·S for the right) by HFOV (sinusoidal, 10Hz, 50ml) at the end of 1 second

Geometric shape of airways ? Viscosity ?

1 second comparison HFOV with normal air HFOV with much more viscous air f (Frequency) 10Hz 10Hz TV (Tidal Volume) 50ml 50ml Local TV 50ml/218 50ml/218 Gas viscosity 1.983E-5Pa·S 1.983E-3Pa·S Replaced Volume 3.12E-5ml 3.56E-5ml Fresh gas movement deep deep

6th mode depends on VISCOUSITY ?

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For the case of 150ml tidal volume oscillated with 10Hz

• frequency. Within the area between G18 and G20:

Fig.51 Re, Pe, and Wo numbers for TV=150mL at each generation. (Yamamoto, 2010) Re<10, Wo<1, Pe≈1 indicates that viscous laminar flow and parabolic quasi-steady flow are dominant in this region, advective transport rate and diffusive transport rate are in the same order of magnitude.

Viscosity ? Geometric shape of airways ?

6th mode, Raking Effect’ is effective at more high frequency ?

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32 4.2 Numerical calculation (effect of super-high-frequency)

• 4. PRELIMINARY INVESTIGATION OF SUPER-

HFOV

Fig.66 Particle oscillation at G18 by HFOV (sin, 20Hz, 25ml, left) (sin, 50Hz, 10ml, middle) (sin, 75Hz, 6.7ml, right)

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• 4. PRELIMINARY INVESTIGATION OF SUPER-

HFOV

Sinusoidal, 100Hz, 5ml Sinusoidal, 100Hz, 10ml Sinusoidal, 100Hz, 20ml

Fig.67 Lagrangian and VOF calculation at G18 by HFOV (sin, 100Hz, 5ml, left) (sin, 100Hz, 10ml, middle) (sin, 100Hz, 20ml, right)

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Raking effect is effective with frequency increasing (Super-HFOV) An local region exists where the raking effect is excited. However, we did not identify it yet.

Conclusion 3 Conclusion 4

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2nd Problem Coanda effect simulation

Drag reduction of motor vehicles by active flow control using the Coanda effect, D. Geropp, H.J. Odenthal, Exp. In Fluids, 28(2000) 74-85. Design methods of Coanda effect nozzle with two streams Michele TRANCOSSI*,1, Antonio DUMAS1, Shiam Sumantha DAS2, Jose PASCOA2 , INCAS BULLETIN, Volume 6, Issue 1/ 2014, pp. 83 – 95

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Flow

Molecular force

Why Coanda effect is problem ?

Continume Viscous Separation Bending Continuous derivative Boundary layer Separation Momentum transfer

Continuity N-S equations

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Usual No-slip

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Slip

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What happens at the starting ?

Usual No-slip

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Slip

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Conclusion 5

Experimental simulation trial including the potential flow analysis is fruitful like a discussion on Coanda effect. Also, criteria of continuity condition should be examined within CFD.