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Unformatted text preview: 0.4 nm Displacement distance 1 pm Molecular Velocity 10 3 m/s 8/22/2006 ME509: Fluid Mechanics 4 The Smallest Length Scale of a Continuum (Deen, Analysis of Transport Phenomena, 1998) Average over sufficient number of molecules – Point quantities, , u , T – Random process theory • N ~ 10 4 molecules – L ~ 70 nm (gases at STP) – L ~ 8 nm (liquids) Point Value Macroscopic Value Averaging Volume ~ L 3 2 / 1 N x 8/22/2006 ME509: Fluid Mechanics 5 The Smallest Length Scale of a Continuum (Deen, Analysis of Transport Phenomena, 1998) Length scale of molecular interactions (transport properties, , , D ) – Gases: mean free path ~ 100 nm – Liquids: molecular diameter ~ 0.3 nm Average over ~ 10 3 interaction length scales – L ~ 1 m (gases) – L ~ 3 nm (liquids) Taking the max of these two types of quantities – L ~ 1 m (gases) – L ~ 10 nm (liquids) 8/22/2006 ME509: Fluid Mechanics 6 GadelHak, 1999...
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This note was uploaded on 10/09/2011 for the course ME 509 taught by Professor Wereley during the Fall '11 term at Purdue.
 Fall '11
 Wereley
 Shear, Stress

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