Micro/Macro mass flow near a surface
Micro/Macro mass flow near a surface
(OP)
1/ Consider - a ball bearing hitting a flat surface - it will bounce off at the angle of incidence similar to a light bean on a mirror.
2/ On a molcular scale there is no flat solid surface (because of surface roughness) so an individual atom will hit a many angled rough surface and can bounce off at any direction depending on the "angle" of the surface where the contact occurs.
3/ Assuming 1& 2 above are correct - what happens when a large mass of molecules (say 10^20)are travelling in the same direction (say out of a compressed air nozzle)and they contact the rough solid surface. Do the individual molecules bounce off at every direction - BUT - after they bounce off they are swept up by the greater mass flow whice means that all athe molecules "as a mass" bounce off at the same angle(angle of incidence = angle of reflection).
4/ Then there is the "Coanda effect" - maybe ? ?
Can anyone suggest search words or sites/papers on this topic.
Thanks
2/ On a molcular scale there is no flat solid surface (because of surface roughness) so an individual atom will hit a many angled rough surface and can bounce off at any direction depending on the "angle" of the surface where the contact occurs.
3/ Assuming 1& 2 above are correct - what happens when a large mass of molecules (say 10^20)are travelling in the same direction (say out of a compressed air nozzle)and they contact the rough solid surface. Do the individual molecules bounce off at every direction - BUT - after they bounce off they are swept up by the greater mass flow whice means that all athe molecules "as a mass" bounce off at the same angle(angle of incidence = angle of reflection).
4/ Then there is the "Coanda effect" - maybe ? ?
Can anyone suggest search words or sites/papers on this topic.
Thanks





RE: Micro/Macro mass flow near a surface
As for #3, no: molecule-to-molecule collisions become important, and the equations for fluid mechanics (Navier-Stokes) would seem to prevail (you don't state the ambient pressure/density conditions, so it is not clear if this is free molecular flow or ....)
#4, um, unless the impacted surface is moving/rotating, the Coanda effect is not applicable. But there will certainly be wall effects, and a boundary layer. CFD might help.
RE: Micro/Macro mass flow near a surface
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