| 1 |
Replace particle description by average. 1023 molecules in a molar volume is too many to handle numerically. So divide full system into a large number of "small" volumes dV such that:
-
Macroscopic Properties: Temperature, velocity, pressure are essentially constant in volume
|
| 2 |
In principle, use statistical physics (or Particle Dynamics averaged as "Transport Equations") to describe volume dV in terms of macroscopic (ensemble) properties for volume
|
| 3 |
Volume size = dV must be small enough so macroscopic properties are indeed constant; dV must be large enough so can average over molecular motion to define properties
-
As typical molecule is 10-8 cm in linear dimension, these constraints are not hard
-
Breaks down sometimes e.g. leading edges at shuttle reentry etc. Then you augment continuum approach (computational fluid dynamics) with explicit particle method
|
