Graphics for "Fluids
and Friction in the Nanoworld"
Uzi Landman, Georgia Institute of Technology
Nanotechnology Seminar: AAAS Annual Meeting
For Immediate Release
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| Uzi Landman portrait in his lab at Georgia Tech. Image on computer is an early molecular dynamics simulation of a gold tip forming a junction when placed into contact with a nickel plate. |
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| Molecular dynamics simulations show how oscillating the gap between two sliding surfaces reduces the order of thin-film lubricant molecules. In the lower image, molecules that had been confined within the surface have moved out into the bulk lubricant not confined, and molecules from the bulk areas have moved into the gap. |
Nano-elastohydrodynamics: stucture, dynamics and flow in non-uniform lubricated junctions. |
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Copyright: Science |
Copyright: Science |
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| (A) Molecular
dynamics simulations of a propane nanojet formed through injection
into vacuum through a convergent 3-D gold nozzle. (The upper solid
gold walls were removed to expose the interior of the nozzle). The
sequence of configurations depicts the initial exit of the propane
fluid (10 ps) and wetting of the outside surface of the nozzle to
form a thin adsorbed propane film, accompanied by swelling of the
exiting fluid propane jet near the nozzle exit. The jet achieves a
flow velocity of 200 meters/sec and is accompanied by evaporative
cooling, with steady state achieved at about 1 ns. The propane molecules
are depicted in blue; the gold atoms are in yellow.
(B) Evolution of the propane nanojet along the direction of propagation after exit from the nozzle. Formation of fast moving droplets and molecular clusters is observed at the initial (transient) state, achieving steady-state flow conditions. Molecular evaporation and formation of necking instabilities are observed, leading to breakup events and formation of drops. At pinch-off, the droplets are of elongated ellipsoidal shape and they round-up shortly after. In the inset, the time evolution of the intact length of the jet is shown. Each saw-tooth discontinuity corresponds to a pinch off of a drop. |
(A-C) Selected atomistic configurations obtained via molecular dynamics simulations with a wetting 6 nm diamater nozzle, illustrating various breakup scenarios. In each frame, two consecutive times are shown. The most frequently observed breakup process, exhibiting close to pinch-off formation of an axis-symmetric double-cone shape of the neck, is displayed in (B). Also shown is (A) occasional formation of a non-axisymmetric neck-configuration or (C) generation of a somewhat elongated neck resulting in split-off of a small cluster. (D) Results pertaining to breakup events of the propane jet for the above non-wetting nozzle obtained via an atomistic molecular dynamics simulation (top); a simulation using the deterministic lubrication equations LE; a simulation of the stochastic LE, SLE. Note the double-cone neck shapes exhibited in the MD and SLE simulation, on contrast to the long thread obtained with the LE. (E) shows the time evolution of the intact jet length L (upper curve) and for the minimal jet radius (bottom curve). |
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(Photo by Gary Meek, Georgia Tech Research Corporation) |
(Photo by Gary Meek, Georgia Tech Research Corporation) |
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| Uzi Landman (l) and Michael Moseler display a sequence of simulations showing the exit of propane from a nozzle just six nanometers in diameter. | Uzi Landman (l) and Michael Moseler display a sequence of simulations showing the exit of propane from a nozzle just six nanometers in diameter. |
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(Photo by Gary Meek, Georgia Tech Research Corporation) |
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| Uzi Landman (l) and Michael Moseler display a sequence of simulations showing the exit of propane from a nozzle just six nanometers in diameter. |
For More Information:
John Toon (404-894-6986); E-mail: (john.toon@edi.gatech.edu);
Fax (404-894-4545)
or Jane Sanders (404-894-2214); E-mail: (jane.sanders@edi.gatech.edu);
Fax: (404-894-6983)
| Send questions and comments regarding this page to rnpo@edi.gatech.edu Last updated: February 7, 2001 |
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