Hallo Stefan.
Also probiert hab ich so was noch nie.
Ob die Problematiken beliebig skalierbar sind bezweifel ich ein wenig.
Man müsste wohl auch boundaries: real wall vergeben.
Kann man bei den zu untersuchenden Luftströmungen noch von kontinuierlich reden ?
Wie sieht es mit der Knudsen-Zahl aus ?
Vergleiche hier (aus der Knowledge Base):
Discussion
Computational Fluid Dynamics (CFD), including COSMOSFloWorks, is based on continuum flow, in which the number of molecules per unit volume is assumed large enough so that in general, the fluid properties could be assumed to vary continuously from point to point throughout a region.
For example at 14.7 psi (1 atmosphere) the mean free path (mean distance between molecular collisions) is only 2.6e-6 in. The assumption of a continuum however breaks down at very low pressures where the mean free path becomes comparable or greater in length than the length of a body or other object under consideration. For example, at a pressure of 1.5e-5 psi, the mean free path increases to 2.5 inches. At this pressure, we can no longer speak of the fluid as a continuum.
The Knudsen number (Kn) relates the mean free path in a flow to the characteristic length of a body immersed in the flow.
Kn = l / L
Where:
l = mean free path (m)*
(* For particle dynamics in the atmosphere, and assuming standard temperature and pressure, i.e. 25°C, 1 atm, we have λ = 8×10-8 m. )
L = representative physical length scale (m)
For Continuum flows, Kn should be less than 0.01.
For instance, if your application is at 2e-5 psi the Kn is most likely greater than 0.01 and we can no longer speak of the fluid as a continuum.
Roland
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* Keymaster of the Masterkey *
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