Molecular dynamics studies of anomalous transport in rarefied gas flows

Nishanth Dongari, Yonghao Zhang, Jason Reese

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Abstract

We investigate the thermodynamically non-equilibrium gas dynamics by measuring molecular free path distribution functions, inter-molecular collision rates and wall dependent mean free path (MFP) profiles using the molecular dynamics (MD) method. The simulations cover a wide range of fluid densities for single-wall case, parallel walls cases and a cube with all periodic walls. The simulations are validated by deducing the theoretical unconfined MFP values at standardpressure and temperature conditions. The free path MD measurements of individual molecules convey that conventional exponential distribution function is not valid under rarefied conditions and molecules follow L´evy type flights, irrespective of the presence of a wall. MFP profile measurements for confined planar surfaces in the transition flow regime show
sharp gradients close to the wall, while theoretical models predict shallower gradients. As gas transport properties can be related to the MFP through kinetic theory, our MD data may help to modify the constitutive relationships, which may
then be fed into the Navier-Stokes equations for better effective modeling of micro gas flows in the transition flow regime.
Original languageEnglish
Number of pages10
Publication statusPublished - 8 Dec 2010
Event2nd European Conference on Microfluidics - Toulouse, , France
Duration: 8 Dec 201010 Dec 2010

Conference

Conference2nd European Conference on Microfluidics
CountryFrance
CityToulouse,
Period8/12/1010/12/10

Keywords

  • rarefied gas flows
  • free path distribution
  • L´evy flights
  • mean free path
  • molecular dynamics

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