Fluid Mechanics for Microand Nano Technologies

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Fluid Mechanics for Micro-and Nano- Technologies

• By
• Dr. Alex Povitsky
• Department of Mechanical Engineering
• University of Akron
• E-mail povitsky_at_uakron.edu, Room 108-C

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Micro- and Nano-flows

• Knudsen number is 0.1-5.0 No-No-Slip/slip
  boundary conditions
• Navier-Stokes/Burnett equations

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Carbon nanotube-polymer of pure carbon

• Stiffness-to-weight ratio forty times higher than
  that of aluminum
• Strength-to-weight ratio five hundred times
  higher than that of aluminum
• Thermal conductivity as high as diamond
• Electrical conductivity six orders-of-magnitude
  higher than copper

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Nanotubes Properties Uses

• Conductive plastics
• Energy storage
• Molecular electronics
• Thermal materials
• Fibers and fabrics
• Catalyst supports

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ExampleChemical Vapor Deposition method (CVD)
for synthesis of nanotubes
Base growth model
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Computational framework for CVD process
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Micro-fluids aspects of feedstock gas flow at
the nanotubes base
Slip boundary conditions
No-slip boundary conditions
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Various mixing scenario
90O
30O
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Improved Showerhead of the HiPco Reactor
60O
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Typical trajectories of catalyst particles for
high-incidence jet mixing
1-trajectory bends inwards 2-trajectory bends
outwards 3-particle rotates upstream of the jet
intersection point
Can we design a mixing device to achieve as much
trajectories (2) as possible?
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Laser-Ablation SWNT Process at NASA Johnson Space
Center

• Dual concentric quartz tubes
• Pulse laser at 532 nm wavelength and 5mm beam
  diameter
• Target graphite and catalyst (Ni and Co)
• Non-reacting surrounding argon flow at T1473 K

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Plume formation in laser ablation
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Ablation
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Propagation of plume
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Evolution of plume and formation of nanotubes
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Influence of injection velocity on multi-pulse
plume
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Conclusions and Future Research

• CFD modeling of nanotubes synthesis requires
  multi-scale approach
• continuous mechanics of feedstock gas or plume
• micro-fluidic flow about isolated nanotubes,
• molecular dynamics of formation of plume in laser
  ablation.

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References
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Other research topic Aeroacoustics

• High-order spectral-type schemes are used
• Landing gear noise and its reduction (with
  Bombardier Aerospace and NASA)
• Amplification of sound due to upstream
  propagation of waves
• Effect of vortex profile on directivity of sound
• in blade-vortex interaction (BVI)

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Sources of airframe noise
The flap side-edge vortex is a major source of
sound
Blade-vortex interaction
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The RMS of Acoustic Pressure for Taylor and
Vatistas models