Flow of Fluids and Solids at the Nanoscale Thomas Prevenslik QED Radiations Discovery Bay, Hong...
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Transcript of Flow of Fluids and Solids at the Nanoscale Thomas Prevenslik QED Radiations Discovery Bay, Hong...
Flow of Fluids and Solids at the Nanoscale
Thomas Prevenslik
QED Radiations
Discovery Bay, Hong Kong, China
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
1
The Hagen-Poiseuille equation of classical fluid flow that assumes a no-slip condition at the wall cannot explain the
dramatic increase in flow found in nanochannels.
Even if slip is assumed at the wall, the calculated slip-lengths are found exceed the slip on non-wetting surfaces by 2 to 3
orders of magnitude.
Similarly, MD simulations of nanochannel flow cannot explain the flow enhancement.
MD = molecular dynamics.
Introduction(Fluids)
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
2
Introduction(Solids)
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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In solids, classical kMC cannot explain how crystals in a nanotube under the influence of an electric current flow through a constriction that is smaller than the crystal
kMC = kinetic Monte Carlo.
However, QM and not classical physics governs the nanoscale.
QM = quantum mechanics.
At the nanocale, fluid and solid atoms are placed under EM confinement that by QM requires their heat capacity
to vanish.
EM = electromagnetic.
QM v. Classical Physics
Unlike classical physics, QM precludes the conservation of viscous and frictional heat in fluid and solid atoms by the
usual increase in temperature.
MD and kMC based in classical physics therefore require modification for QM at the nanoscale.
Conservation of viscous and frictional heat proceeds by QED inducing creation of EM radiation that ionizes the atoms to cause atomic separation under
Coulomb charge repulsion.
QED = quantum electrodynamics.
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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Approach
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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MD simulations of liquid argon flow in a nanochannel show the viscosity to vanish suggesting the flow is upper bound by the
frictionless Bernoulli equation
Simplified extension of Bernoulli equation to the flow of a solid crystal through a nanotube suggests cohesion to vanish,
Fluid and solid at the nanoscale flow as a loosely bound collection of atoms under Coulomb repulsion
Heat capacity of the atom
TIR Confinement of Nanostructures
Conservation of energy and momentum
Theory
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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Heat Capacity of the Atom
7
kT 0.0258 eV
0.00001
0.0001
0.001
0.01
0.1
1 10 100 1000
Pla
nck
Ene
rgy
-E
-eV
Thermal Wavelength - l - microns
Classical Physics (MD, Comsol)
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
l
l1
kT
hcexp
hc
E
Classical Physics (MD, Comsol)
QM(kT = 0)
At the nanoscale, the atom has no heat capacity by QM
Nanostructures have high surface to volume ratio
Absorbed EM energy temporarily confines itself to the surface to form the TIR confinement
QED converts absorbed EM energy to standing waves that ionize the nanostructure or escape to surroundings
f = ( c/n) / / 2 = d E = h f
TIR Confinement
8Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
Heat
dIonization
QED
Radiation
QED
Radiation
Surface Absorption / 2
Standing Wave
Conservation of Energy
Lack of heat capacity by QM precludes EM energy conservation in discrete molecules and nanostructures
by an increase in temperature, but how does conservation proceed?
ProposalAbsorbed EM energy is conserved by creating QED induced excitons (holon and electron pairs) at the TIR
resonance
Upon recombination, the excitons emit EM radiation that charges the molecule and nanostructure or is lost to the
surroundings.
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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Conservation of Momentum
Absorption of EM energy photon velocities vanish
Excitons are created at zero velocity
Momentum of photons = Momentum of excitons = 0
Momentum is conserved because EM energy is absorbed
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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Frictionless Fluids / Solids
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
Pot
enti
als
Atom
QEDCharge
Zero
Atom + QED Charge
QED charge makes atomic attraction vanish = 0
11
MD v. QM
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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MD assumes the atoms have thermal kT energy or the heat capacity to conserve EM energy by an increase in
temperature, but QM does not
QM requires the Nose-Hoover thermostat to maintain the model at constant absolute zero temperature.
Classically, temperature creates pressure. QM requires the temperature to create excitons and charge that
produces repulsive Coulomb forces between atoms.
MD Simulation
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
Usually, MD solutions of nanochannel flow are performed with Lees and Edwards periodic boundary conditions.
But charging the atoms requires long range corrections that may be avoided by using a discrete MD model and
considering all atoms without a cut-off in force computations
13
Lennard-Jones Potential
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
The L-J simulation of the atomic potential
s = repulsive = attractive
The L-J potential minimum occurs at R = 21/6
ULJ = - .
14
Electrostatic Force
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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The electrostatic energy UES from the QED induced charge
𝑈 𝐸𝑆=𝑒2
4𝑜𝑅
𝑐=𝑈𝐿𝐽
𝑈 𝐸𝑆
=421 /6𝑜
𝑒2
The fraction c of UES to counter the attractive potential
F= , < c The electrostatic repulsion force F between atoms
Temperature
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona 16
MD simulations valid by QM require the viscous heat is not conserved by an increase in temperature
MD solutions are therefore made near absolute zero temperature, say 0.001 K to avoid temperature dependent
atom velocities.
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
The BCC configuration assumed a discrete 2D model of 100 atoms of liquid argon in a 32.6 A configuration.
17
Model
Loading
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
The MD loading was a velocity gradient normal to the flow of 100 m/s over the height of the MD box.
Unlike Lees-Edwards, the MD computation box is distorted after 25000 iterations
(Solution 150000 iterations)
18
The fraction c of the available electrostatic energy UES to counter the attractive potential is,
Taking = 120 k for argon, the fraction c = 0.0027.
MD Solution
19Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
MD Results
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
20
-10000 10000 30000 50000 70000 90000 110000 130000 150000-1.2E-03
-1.0E-03
-8.0E-04
-6.0E-04
-4.0E-04
-2.0E-04
0.0E+00
2.0E-04
4.0E-04
Iteration
Vis
cosi
ty [
Pa-
s]
MD solutions were obtained for various to determine the optimum at which the viscosity vanished
h = 0.0006 < c = 0.0027
Collectively, 4 pairs of atoms participated
in reducing 2 atom friction
Experimental Data
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona 21
= QM / QM, 0
QM is the actual flow QM,0 is the Bernoulli equation
Conclusions
22Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
High flow in nanochannels is the consequence of QM that requires the heat capacity of the atom under EM confinement to vanish and negate the conservation of viscous heat by an
increase in temperature.
Instead, the viscous heat is conserved by QED inducing the creation of EM radiation that ionizes the fluid molecules to produce a state of Coulomb repulsion that overcomes the
attractive potential between atoms.
Nanochannels produce frictionless Bernoulli flow as the fluid viscosity vanishes and reasonably supports experiments.
Flow of Solids
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
Iron crystals under an electric current fit through a constriction in the nanochannel that is smaller than the crystal itself ?
23
Classical kMC atom has kT energy invalid by QM
But as kT 0, V 0, the crystal does not move.
kMC Solutions
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
Flow of metal crystals through smooth uniform nanochannels is generally thought caused by electromigration based on kMC
24
Analysis
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
Instead of temperature changes, QED conserves the Joule heat to charge all atoms in crystal
For a voltage difference V* acting across nanotube length L, the force F across a crystal atom of cubical dimension b
having charge q = unit electron charge,
F=q V∗
Lb
25
Bernoulli Equation
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
V=√ 2 P
=√2qV ∗
b L
The pressure P across the atom is, P = F / b2
giving the atom velocity V
Experiment V = 1.4 micron/s , L=2 micron, V* = 0.2 Volts
For iron, b =0.22 nm, = 7880 kg/m3 V = 135 microns/s 2 orders of magnitude higher !!!
Only 1% of crystal atoms are charged ? Fe (n=1.25) < CNT graphite (n=2.5) Rerun tests with Si (n=3.2) crystal ?
26
Questions & Papers
Email: [email protected]
http://www.nanoqed.org
Proc. 2nd Conference on Heat Transfer Fluid Flow, HTTF'2015, 20-21 July, Barcelona
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