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Stenosis Presenation by Dr. Pitchumani and Jie Chen
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Sampling of Research at the Advanced
Materials and Technologies Laboratory
Presented at the VBI Faculty Meeting • November 10, 2009
Ranga PitchumaniAdvanced Materials and Technologies Laboratory
Department of Mechanical Engineering
Virginia Tech
Blacksburg, Virginia 24061-0238
[email protected] • http://www.me.vt.edu/amtl • (540) 231-1776
Advanced Materials and Technologies LaboratoryProf. Ranga Pitchumani • [email protected] • http://www.me.vt.edu/amtl
Research focuses on the fundamentals of multiscale, multiphysics phenomena in
the fabrication of composite materials via liquid molding and other methods. The
emphasis is on filling gaps in understanding of the phenomena, bridging them
across a cascade of scales, and using computational physics-based models for real-
time sensing and control, design, optimization, and analysis under uncertainty.
Use of carbon nanotubes in structural fiber-reinforced composites is studied for
their damping characteristics for applications in vibrating and rotating structures
(such as rotorcraft and wind turbine blades). Related issues on characterizing the
complex rheology and cure kinetics of resin systems with carbon nanotubes are also
addressed.
Composite Materials and Nanocomposites
100%
A/W=1709 m2/g
Blood flows through stenosed carotid and coronary arteries with a
complete bypass graft are investigated by using computational fluid dynamics
tools. Different anastomotic angles, bypass graft length and locations of the
stenosis are analyzed as function of the extent of plaque occlusion in the artery.
The effects of type-II diabetes mellitus is also investigated. The results show that
the flow features, including pressure drop cross the stenosis and the shear stress on
artery walls, are all influenced by these parameters; a systematic analysis is
conducted to derive information on graft design so as to minimize the possibility of
the restenosis in the host artery with bypass graft implantation.
Bio Transport
Phenomena A novel process for replication of
electroforming micromolds for use
in high aspect ratio micropart
fabrication is being studied in
collaboration with Sandia National
Laboratories. A combined
computational and experimental study
on the fundamental phenomena
governing the fabrication process is
used to systematically elucidate the
effects of the various process, material,
and geometric parameters, including
the interactive effects of uncertainty
inherent in the materials and the
process toward predicting the resulting
process variability and the micropart
quality. Optimum processing conditions
are derived for robust and reliable
processing.
Microfabrication
Programs in the area of energy focus on fuel cells, hybrid systems,
photovoltaics and thermal energy storage. The projects on fuel cells are
aimed at designing the cell and the systems for uniformity of current density
through optimal design of the operating conditions as well as through novel
material designs such as graded material microarchitectures. Passive air-
breathing fuel cell designs are developed for reduced system complexity and
novel microfuel cells that combine microfabrication and fuel cell technologies
are investigated for micropower generation at high power density. Transient
operation of fuel cells and fuel cell/battery and fuel cell/gasoline hybrid
systems are also being investigated to design systems for tracking varying
power requirements in different applications. Research on photovoltaics is
on understanding the fundamentals of dye-sensitized solar cells (DSSC) or
Grätzel cells with a view to develop design maps for applications in different
terrestrial locations. Thermal energy storage technologies based on phase
change materials are being developed for concentrating solar power systems.
The novel approach involves embedding thermosyphons or heat pipes to reduce
the resistance to heat transfer between the location where phase change occurs
and the working fluid of the power cycle.
Energy
As microsystem technologies and
application prospects continue to grow,
it is of interest to fabricate high aspect
ratio microstructures from a broad
range of metals and ceramics. The
objective of the work is to investigate a
new technique based on capillary-
driven microcasting and curing of
an epoxy-based metallic or ceramic
nanoparticulate slurry into a sacrificial
plastic mold, and subsequent sintering
of the nanoparticulate ceramic or
metallic phase to form the micropart.
Fundamentals of microchannel filling,
nanoparticle settling during flow, and
nanoparticulate preform sintering are
investigated to arrive at operating
windows on slurry formulations, mold
design, mold filling parameters, and
sintering conditions so as to maximize
feature fidelity.
Advanced Materials and Technologies Laboratory
Blood Flow Through Stenosed Arteries with Complete Bypass
Atherosclerosis—the constriction of an artery
through plaque buildup—is a leading cause of
human mortality in developed countries. Bypass
surgery is used to improve blood flow around a
diseased artery.
The goal is to study blood flow in a stenosed
artery with bypass with the objective of
developing bypass design guidelines.
Bypass parameters were varied in a
computational simulation study to assess their
influence on the pressure drop and wall shear
stress
Anastomosis Angle: α, Anastomosis Length: L
Occlusion: 1Astenosis
Ahost
1d
D
2
r v 0
r v
r v p Ý
r v
r v T
Artery Carotid (D = 6 mm; 370
ml/min flux)
Coronary (D = 3 mm; 35
ml/min flux)
20%, 50%, 75% and 100%
15o, 30o, 45o, and 60o
L/D 4, 6 and 8
Carreau model:
Blood Rheology
Advanced Materials and Technologies Laboratory
L = 8D
Axial Velocity Profiles
45o = 75%
L = 4D
L = 6D
Carotid Artery
Coronary Artery
45o = 75% L 4D
Carotid Artery
Bypass Ratio
1.77
Bypass Ratio
1.61
Bypass Ratio
1.48
Advanced Materials and Technologies Laboratory
Axial Velocity Profiles in the Carotid Artery
= 20%
45o L = 4D
= 50%
= 75%
= 100%
= 15o
= 30o
= 45o
= 60o
75% L = 4D
Advanced Materials and Technologies Laboratory
Pressure Drop in the Carotid Artery
Advanced Materials and Technologies Laboratory
Minimum Wall Shear Stress in the Carotid ArteryM
inim
um
Wa
ll S
he
ar
Str
ess,
min
[Pa
]
Min
imum
Wall
Shea
r S
tress,
min
[Pa]
min
Advanced Materials and Technologies Laboratory
Bypass Design Plots
Carotid Artery
Coronary Artery
p po
p po
po 129.3Pa
p po
po 101.5Pa
p po
Carotid Artery
Coronary Artery
po is the pressure drop in a
healthy non-stenosed artery
without bypass
Advanced Materials and Technologies Laboratory
Bypass in Patients with Type 2 Diabetes Mellitus