19% 11% 4% 49% vein PTFE artery. Experimental Characterization of Transitional Unsteady Flow Inside...

19%

11%4%

49%

vein

PTFE

artery

Experimental Characterization of Transitional Unsteady Flow Inside a Graft-to-Vein Junction

Nurullah Arslan

Mechanical Engineering DepartmentThe University of Illinois at Chicago

Argon-Ion laser750mW Downstream tank

Upstream Tank

Test section

LDA probe Radiator Heater

PumpBall valve

90%

10%

Ball valve

Graft

PVSDVS

Color Doppler Ultrasound

QMAX 2.5 l/min

QMEAN 1.5 l/min

QMIN 1 l/min

10%

AV Graft Image Taken by Color Duplex Ultrasound

Schmidt et al., Vascular Access for Hemodialysis, 1985

Arterio-Venous (A-V) GraftsHemodialysis Patients

PTFE Graft just after Implantation(Reference: Access Surgery, 1982)

Hemodynamics low and oscillating WSS

Arterial Bypass Graft Failure

Tissue growthThickening of the vessel wall

Intimal Hyperplasia

Stenosis (narrowing of the vessel)

FailureBlockage stops blood flow

Thrombosis (blood clot)

Arterial PTFE Graft Model(Loth et al.)

Similar Geometry but different flow conditions

Re=222

IH Distribution for Arterial Grafts

LDA Results for Arterial Graft

Results Under Arterial Flow ConditionsRemean=222 (Loth et al.)

Summary:

1) No Turbulence

2) No separation was observed

3) Flow was complex with strong secondary flow patterns

4) Pulsatility affected the flow field greatly (velocity profiles were more blunt)

5) WSS values were generally low in the anastomosis

Hemodynamics Turbulence & WSS

Events Leading to AV Graft Failure

Energy Transfer to the wallTissue Vibration

Enthothelial Cell Damage

Tissue growthThickening of the vessel wall

Intimal Hyperplasia

Stenosis (narrowing of the vessel)

Increased turbulencePlatelet activation

FailureBlockage stops blood flow

Thrombosis (blood clot)

DVS

Floor

PVS

A-V GraftHood

Heel(Apex)

Toe

+x/D0-x/D

Graft to Vein Junction

Fillinger et al., Hemodynamics and Intimal Hyperplasia, 1991

Canine AV Graft Study

(A) 3-D schematic representation of perianastomotic tissue vibration. (B) Schematic representations of longitudinal(C) Transverse views of perianastomotic tissue vibration

Stenosis Location inside the A-V graft

Re10-3

Thickness (mm)

Fillinger Concluded

1) Tissue vibration

2) Reynolds Number

intimal hyperplasia at the venous anastomosis

(2D) 29 Apr 1998

-6.4 -3.2 0 3.2

(2D) 29 Apr 1998

Other AV Graft Model Studies(No turbulent measurements)

Velocity measurements and WSS estimation (Shu et al.)

Velocity patterns by flow visualization (Krueger et al. )

Flow patterns using flow visualization (Bakran et al.)

Turbulence StudiesTurbulence measurements in

constricted tubes (Deshpande et al., 1980, Jones et al., 1985, Kehoe et al., 1990)

High Reynolds stresses may cause red blood cell damage and platelet activation (Sutera, S.P. and Mehrjardi, M.H., 1975)

Stenosis

Objective

To determine the distribution of turbulence and Reynolds stresses

within the an AV graft using in vitro modeling techniques

Summary of In Vivo Measurements

Patient I Patient IIGraft Diameter(mm) 6 6.7 Umax(m/s) 1.5 1.2 Umin(m/s) 1 0.8Remax 2700 2400Remin 1800 1600Qmax(ml/min) 2544 2525Qmin(ml/min) 1696 1683Womersley number() 4.8 5.3

Re = VD/, Q = VA, A = R2

= R(2 f/µ)1/2

µ=3.5 mPa/s, =1.05 g/cm3

Methods

In Vitro MeasurementsBifurcation plane and plane

Flow Division: DVS:Graft = 10:90

Steady Flow

Re = 1060, 1820, 2530, 2720

umean, vmean, urms, vrms, u´v ´

Pulsatile Flow

Repeak= 2470, Remean= 1762

uens, vens, urms, vrms, u´v´ as ƒ(t)

(2D) 23 Oct 1998

-6 -5.2 -4.4 -3.6 -2.8 -2 -1.2 -0.4 0.4 1.2 2 2.8 3.6

x x xx

xx

x

x x x x x x x x x x x x x

-6.6

x

y

z

(2D) 23 Oct 1998

Measurement Locations in A-V Graftx indicates measurements lines perpendicular to the plane of bifurcation

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-1 -0.5 0 0.5 1

Radial position (r/R)

No

nd

ime

nsi

on

al v

elo

city

(u

/Um

ax)

LDA measurements

Theoretical Parabolicprofile

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-1 -0.5 0 0.5 1

Radial Position (r/R)

Non

dim

ensi

onal

vel

ocity

(u/U

max

)

LDA measurements


GRAFT inlet DVS

Velocity Profiles at Graft Inlet and DVSRe=1060

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-1 -0.5 0 0.5 1


No

nd

ime

nsi

on

al v

elo

city

(U

/Um

ax)

LDA Measurements

Theoretical Parabolic profile

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-1 -0.5 0 0.5 1


Non

dim

ensi

onal

vel

ocity

(U/U

max

)

LDA Measurements


GRAFT inlet DVS

Velocity Profiles at Graft Inlet and DVSRe=2530

Flow rates in Graft and DVS

0

500

1000

1500

2000

0 60 120 180 240 300 360

Phase Angle (degrees)

Flo

w R

ate

(ml/m

in)

Flow rate, Graft

Flow rate, DVS

In Vitro Flow Wave Form at Graft inlet and DVS (Graft:DVS = 85:15)

Velocity Profiles at Systolic Acceleration and Peak

-1 -0.5 0 0.5 1

r/R

U/U

max

Theory

LDA measurments Phase Angle=30)

-1 -0.5 0 0.5 1

r/R

U/U

max

Theory

LDA measurements Phase Angle=60)

Velocity Profiles at Systolic Deceleration and Diastole

-1 -0.5 0 0.5 1

r/R

U/U

max

Theory


-1 -0.5 0 0.5 1

r/R

U/U

max

Theory


Results Under AV Flow Conditions

1) Separation

2) Turbulence

3) Secondary Flow

4) Pulsatility

5) WSS

Midplane Velocity Vectors Re = 1060

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

02m/s

(a)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(b)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(c)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

0500dynes/cm2

(d)

Midplane Velocity Vectors Re = 1060 and 2530

-6.6

-6.6

-6.6

-6.6 -0.40.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0500dynes/cm2

(d)

-0.40.4 1.2 2 2.8 3.6 4.4

0 5m/s

(a)

-0.40.4 1.2 2 2.8 3.6 4.4

00.5m/s

(c)

-6.6

-6.6

-6.6

-6.6

-0.40.4 1.2 2 2.8 3.6 4.4

0 5m/s

(a)

-0.40.4 1.2 2 2.8 3.6 4.4

00.5m/s

(b)

-0.40.4 1.2 2 2.8 3.6 4.4

00.5m/s

(c)

-0.40.4 1.2 2 2.8 3.6 4.4

03000dynes/cm2

(d)

Separation Bubble

~0.1 Dv

(2D) 31 Oct 1998 (2D) 31 Oct 1998

PVS

Toe <1.0 Dv

-6 .6

-6 .6 -1 .2 -0 .4 0 .4 1 .2 2 2 .8 3 .6 4.4

0 4 m/s

(a)

-1 .2 -0 .4 0 .4 1 .2 2 2 .8 3 .6 4 .4

0 0 .5 m/s

(b)

Mean Velocity in the Plane to the Bifurcation PlaneRe=1060 and 2530

-6.6

-6.6

-6.6

-6.6 -1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 4m/s

(a)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 500dynes/cm2

(d)


1) Separationsmall region near the toe creating a low WSS region

2) Turbulence (Urms, Vrms, and RS)

3) Secondary Flow

4) Pulsatility

5) WSS

Turbulent Fluctuations (Urms) Re = 1060

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

02m/s

(a)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(b)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(c)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

0500dynes/cm2

(d)

Turbulent Fluctuations (Urms)

Re = 1060 and 2530

-6.6

-6.6

-6.6

-6.6 -0.40.4 1.2 2 2.8 3.6 4.4

00.5m/s

(b)

-0.40.4 1.2 2 2.8 3.6 4.4

0500dynes/cm2

(d)

-0.40.4 1.2 2 2.8 3.64.4

0 5m/s

(a)

-0.40.41.2 2 2.83.64.4

00.5m/s

(c)

-6.6

-6.6

-6.6

-6.6

-0.40.4 1.2 2 2.8 3.6 4.4

0 5m/s

(a)

-0.4 0.4 1.2 2 2.8 3.6 4.4

00.5m/s

(b)

-0.40.4 1.2 2 2.8 3.6 4.4

00.5m/s

(c)

-0.4 0.4 1.2 2 2.8 3.6 4.4

03000dynes/cm2

(d)

-6 .6

-6 .6

-1 .2 -0 .4 0 .4 1 .2 2 2 .8 3 .6 4 .4

0 0 .5 m/s

(b)

-1 .2 -0 .4 0 .4 1.2 2 2 .8 3 .6 4 .4

0 0 .5 m/s

(c)

Urms at the Perpendicular Plane Re=1060 and 2530

-6.6

-6.6

-6.6

-6.6 -1.2-0.4 0.4 1.2 2 2.8 3.6 4.4

0 4m/s

(a)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 500dynes/cm2

(d)

Turbulent Fluctuations (Vrms)

Re = 1060 and 2530

-6.6

-6.6

-6.6

-6.6 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 500dynes/cm2

(d)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 5m/s

(a)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-6.6

-6.6

-6.6

-6.6

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 5m/s

(a)

-0.4 0.4 1.2 2 2.8 3.6 4.4

00.5m/s

(b)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 3000dynes/cm2

(d)

-6 .6

-6 .6 -1 .2 -0 .4 0 .4 1 .2 2 2.8 3 .6 4 .4

0 500 dynes/cm2

(d)

-1 .2 -0 .4 0 .4 1 .2 2 2 .8 3 .6 4 .4

0 0.5 m/s

(c)

Vrms at the Perpendicular Plane Re=1060 and 2530

-6.6

-6.6

-6.6

-6.6 -1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 4m/s

(a)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 500dynes/cm2

(d)

Reynolds Stress( ) Re = 1060 and 2530

'v'u-6.6

-6.6

-6.6

-6.6 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0500dynes/cm2

(d)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 5m/s

(a)

-0.40.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-6.6

-6.6

-6.6

-6.6

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 5m/s

(a)

-0.4 0.4 1.2 2 2.8 3.6 4.4

00.5m/s

(b)

-0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-0.4 0.4 1.2 2 2.8 3.6 4.4

03000dynes/cm2

(d)

-6 .6 -1 .2 -0 .4 0 .4 1 .2 2 2.8 3 .6 4 .4

0 500 dynes/cm2

(d)

Reynolds Stress( ) at the Perpendicular Plane

Re = 1060 and 2530

-6.6

-6.6

-6.6

-6.6 -1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 4m/s

(a)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 500dynes/cm2

(d)

'v'u



2) Turbulencehigh Urms,Vrms, RS at these Re #s and localized near the toe

3) Secondary Flow

4) Pulsatility

5) WSS

Secondary Flow Field Inside AV Graft

(2D) 05Aug1998

n66 n52 n44 n36 n28 n20

n12 n04 p04 p12 p20 p28 p36

(2D) 05Aug1998

Re=1060

V component of the Velocity, Perpendicular to Bifurcation




3) Secondary Flowstrong and complicated

4) Pulsatility

5) WSS

(2D)21Aug1998

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

05m/s

(2D)21Aug1998

Systolic Peak

Diastole

(2D)21Aug1998

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

05m/s

(2D)21Aug1998

Velocity Profiles at Systolic Peak and DiastoleFlow rates in Graft and DVS

0

500

1000

1500

2000

0 60 120 180 240 300 360


Flo

w R

ate

(ml/m

in)

Flow rate, Graft

Flow rate, DVS


0

500

1000

1500

2000

0 60 120 180 240 300 360


Flo

w R

ate

(ml/m

in)

Flow rate, Graft

Flow rate, DVS

Turbulent Fluctuations (Urms)

Phase Angles 60 and 300

(2D)21Aug1998

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.2 2 2.83.64.4

00.5m/s

(2D)21Aug1998

(2D)21Aug1998

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.2 2 2.83.64.4

00.5m/s

(2D)21Aug1998


0

500

1000

1500

2000

0 60 120 180 240 300 360


Flo

w R

ate

(ml/m

in)

Flow rate, Graft

Flow rate, DVS


0

500

1000

1500

2000

0 60 120 180 240 300 360


Flo

w R

ate

(ml/m

in)

Flow rate, Graft

Flow rate, DVS

Turbulence Intensity for Pulsatile FlowRepeak = 2470 x/D=+1.2

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 10 20 30

Location (mm)

Urm

s (

m/s

)

Systolic AccelarationSystolic PeakSystolic DecelarationDiastoleSteady, Re=1820Steady, Re=2530

Toe side Floor side

-0.5

0

0.5

1

1.5

2

0 5 10 15 20 25 30

Location (mm)

Rey

no

lds

stre

ss *

(0.0

01)

dyn

es/c

m2

Systolic AccelarationSystolic Peak

Systolic DecelarationDiastole

Steady, Re=1820Steady, Re=2530

Reynolds Stress for Pulsatile FlowRepeak = 2470 x/D=+1.2

Toe side Floor side

Animation





4) Pulsatilitysimilar to steady flow results in general with slightly lower turbulence levels

5) WSS

WSS in the Present Study and Low Re# Study (Loth 1993)

(2D)21Oct1998

50

9 247

EstimationofWSS(dynes/cm2)insidethecurrentstudy

(2D)21Oct1998

Results Under AV Flow Conditions1) Separation

small region near the toe creating a low WSS region



4) Pulsatilitysimilar to steady flow results in general with slightly lower turbulence levels

5) WSSgenerally high in graft and PVS

Discussion

-6.6 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

-6.6 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 3000dynes/cm2

-6.6 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

Separation Regions

(2D)21Aug1998

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

05m/s

(2D)21Aug1998

(2D)21Aug1998

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

05m/s

(2D)21Aug1998

Phase=300

Phase=60

Shu et al., 1987 Present Study

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-1 -0.5 0 0.5 1


No

nd

ime

nsi

on

al v

elo

city

(U

/Um

ax)

LDA measurements


Mean Velocity Profiles at Graft Inlet and Upstream of a Constricted Tube

Deshpande(1980)Present study

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

-1 -0.5 0 0.5 1

Urms/Umax

Turbulent Measurements in a Straight TubeU

rms/

Uc

Urm

s/U

c

r/Rr/R

Conclusions Reynolds stress can be high between 1000-2000

dynes/cm2

Turbulent intensity can be high 10-20% Both are focal in our model at the toe inside PVS Secondary flow are significantly altered due to Re number

(as I described before) Pulsatility does not have a dramatic effect due to large

steady component in our mode Pulsatility reduces Urms by greater amount 30% Urms and

15% RS Less turbulent under pulsatile flow Low WSS present, however focal at the toe

FUTURE STUDIES

Clinical Studies

Different models (geometry, elastic, Q)

Vibration experiments (coherent structures)

WSS calculations

Cellular studies (mechanistic approach)

VenafloVenaflo

Nomenclature-AV Loop Graft

ArterialAnastomosis

PTFE Graft(Polytetrafluoroethylene)

VenousAnastomosis

PVS(Proximal vein Segment)

DVS(Distal vein Segment)

+v’

U(y)

+v´

-v´

y

x

Reynolds Stress(u´v´)BL Theory, Schlichting,

7th Ed., page 560

Fluid particles with v´ > 0 arrive at a layer from a region where a smaller u prevails which gives rise to a u´ > 0

Hence u´v´ < 0

Main frame

Slygard model

Shaker

Schematic for the Vibration Experiments(Top view)

Function generator

Power amplifier

No Shaker

0

0.01

0.02

0.03

0 20 40 60 80 100 120

Frequency (Hz)

Power Spectrum

Power spectrum(40Hz)

0

0.01

0.02

0.03

0 20 40 60 80 100 120

Frequency (Hz)

Power Spectrum

Power spectrum(20Hz)

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 20 40 60 80 100 120

Frequency (Hz)

Power Spectrum

Velocity Power Spectra1.2 D from toe, 0.16 D from wall

(2D)31Aug1998

-6.8 -6 -5.2 -4.4 -3.6 -2.8 -2 -1.2 -0.4 0.4 1.2

0 0.7m/s

(2D)31Aug1998

Mean Velocities at the Plane Perpendicular to Midplane (0.8D from hood and 0.5D from floor

Re = 1060)

-6.6

-6.6

-6.6

-6.6 -1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 4m/s

(a)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(b)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 0.5m/s

(c)

-1.2 -0.4 0.4 1.2 2 2.8 3.6 4.4

0 500dynes/cm2

(d)

Turbulent fluctuation (Vrms)

Re = 1060

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

02m/s

(a)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(b)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(c)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

0500dynes/cm2

(d)

Reynolds Stress( ) Re = 1060'v'u

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

02m/s

(a)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(b)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

00.5m/s

(c)

-6.8-6-5.2-4.4-3.6-2.8-2-1.2-0.40.41.222.83.64.4

0500dynes/cm2

(d)

19% 11% 4% 49% vein PTFE artery. Experimental Characterization of Transitional Unsteady Flow Inside...

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Transcript of 19% 11% 4% 49% vein PTFE artery. Experimental Characterization of Transitional Unsteady Flow Inside...