Molecular Basis of Fluid Dynamics

[Tat]

I'm curious if anyone has a reading recommendation on the foundations of phenomena such as diffusion of gas, boyancy etc.. What about the molecular interactions causes these? Can rates of diffusion be derived from mass and temp (under ideal gas circumstances, for instance)? My background is in math, so a math intensive explanation is ok, but any suggestions are appreciated. Thanks.

[OdysseusTheInnkeeper]

Back when I was studying physics, one of the professors explained that the causes of friction at the microscale were not explainable, much less described by mathematics.

Besides some of the macro-scale variables you mentioned, I think diffusion at the molecular level might have to do with the geometry, or even the textures of the molecules involved, as well as their sizes. Molecular bond interactions with the permeable membrane also play a part, too.

[jaycwru]

The stuff you describe is described pretty well with the kinetic theory of gases, (mean free path and such). I have a graduate level physical chemistry book that described a bit of that fairly well (and then went into quantum level descriptions of thermodynamics) I don't have it with me at the moment, so I can't give you a title.

Buoyancy is really a force balance by which weight is balanced with pressure forces. Pressure itself is described by the kinetic theory (again), but for a more practicle description of buoyancy you'd want to look into fluid statics.

Your best bet is to google for terms like fluid statics, mean free path, diffusion and buoyancy, and you'll run into all sorts of class notes for engineering classes.

[Yeshi]

if we speak of fluid dynamics, i think there is no explanation for turbulence at all.

But as stated by posters above, much of the molecular-level behaviour modelling is actually representation of the statistics of the observation.

Do we, and to what level, describe the electromagnetic interactions of the assymetric dipoles the likes of H20 (water)? When and what quantum-level effects come into being and in what order of magnitude are they relevant?

[Schneibster]

Back when I was studying physics, one of the professors explained that the causes of friction at the microscale were not explainable, much less described by mathematics.The professor was wrong.

Friction is the result of a combination of van der Waals forces:

Uneven surfaces' "bumps" meet up with one another as the two surfaces interact, and the van der Waals forces between them resist the motion, while the van der Waals forces between the molecules of each object resist those "bumps" being removed or deformed.
Very smooth surfaces exert attractive van der Waals forces between them.

Between them, these explanations describe all the effects of static and dynamic friction. They are in principle measurable, and individually describable both conceptually and mathematically, and their collective behavior is also statistically describable.

Besides some of the macro-scale variables you mentioned, I think diffusion at the molecular level might have to do with the geometry, or even the textures of the molecules involved, as well as their sizes. Your intuition seems good to me here.

Molecular bond interactions with the permeable membrane also play a part, too.I'm not sure how you meant this, so I can't comment.

[epepke]

if we speak of fluid dynamics, i think there is no explanation for turbulence at all.

Either I don't understand what you're trying to say here, or it's wrong. Turbulence falls straight out of the Navier-Stokes equations.

Predicting exactly what happens in turbulence is difficult because it's chaotic.