experimental simulation trial for human lung's flow...

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 1

Hiroyuki HIRAHARA 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’?

2016/5/09 2

Conventional Way

EFD CFD

V & V

Promoting Way

EFD CFD

Check and Review

For Inovation

3

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.

2016/5/09 4

223 bifurcations makes intricate structure

Fig.2 Delivery of Oxygen and Carbon Dioxide

In the Respiratory System

Oxygen-rich

air from

environment

Nasal

cavitiesPharynx Trachea Bronchi

BronchiolesAlveoli

Oxygen and

carbon dioxide

exchange at

alveoli

BronchiolesBronchi

Trachea PharynxNasal

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 oscillation.

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

observed efficiency in animal or patient studies.

General

2016/5/09 7

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 FlowTaylor

Dispersion

Flow

3. GAS FLOW IN BRONCHIOLES INDUCED BY HFOV

3.1 Introduction of HFOV

2016/5/09 8

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)

9

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

𝑅𝑒 =𝑈𝐿

𝜈=

𝑈

𝜈/𝐿=

Convective speed

Momentum Diffusion speed

𝑃𝑒 =𝑈𝐿

𝛼=

𝑈

𝛼/𝐿=

Convective speed

Molecular Diffusion speed

Peclet number is also important,

𝜈: viscousity

𝛼:𝑚olacular diffusion coefficient

2016/5/09 10Fig.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 ?

2016/5/09 11

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?

only by molecular diffusion? Or by some progressive

delivery?

Fig.6 Illustration of main research region and reachable

area of single tidal volume of HFOV

2016/5/09 12

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 × TVVT (constant) =Basic principle:

Normal HVOV Super-HFOV

2016/5/09 13

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

2016/5/09 15

Fig.9 Setting for VOF

calculation by 2 fluids

(Molecular diffusion neglected)


calculation with 4 fluids


Fig.8 Lagrangian particles setting

at different locations

Gas exchange in ‘Normal Breath’

at different position

2016/5/09 16

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



2016/5/09 17



VOF calculation for Normal Breath

(sinusoidal, 0.2Hz, 500mL) in 5 seconds

2016/5/09 18

5 seconds later


Gas redistribution due to large TV

2016/5/09 19







Fig.22 Lagrangian particles at the same locations of

VOF interfaces in Fig.12

2016/5/09 20Fig.25 Particle fluctuations in G18-G20 by HFOV (sinusoidal, 10Hz, 50mL) in 5 seconds

GAS FLOW IN BRONCHIOLES INDUCED BY HFOV

2016/5/09 21

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

2016/5/09 22

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


2016/5/09 23

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

0 second 0.3 seconds 1 second 5 seconds


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

2016/5/09 25

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

2016/5/09 26

PIV experiment in Real Scale !

Micro-PIV(Particle Image velocimetry) Measurement

2016/5/09 27

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

43

2

Phase locked ensemble averaged profiles

2016/5/09 28

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’

2016/5/09 29

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 ?

2016/5/09 31

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 ?

2016/5/09 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)

2016/5/09 33

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)

2016/5/09 34

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

35

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

36

Flow

Molecular force

Why Coanda effect is problem ?

Continume Viscous

SeparationBending

Continuous

derivative

Boundary layer

Separation

Momentum

transfer

Continuity N-S equations

37

Usual No-slip

38

Slip

39

What happens at

the starting ?

Usual No-slip

40

Slip

41

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.

experimental simulation trial for human lung's flow...

Documents