The discussion revolves around the concept of a "fluid particle" as an abstraction in fluid dynamics, exploring its meaning and implications in the context of fluid behavior at both macroscopic and microscopic levels. Participants examine the distinction between real particles (molecules) and the abstract representation used in fluid dynamics.
Participants express differing views on the interpretation of "abstract" and its relationship to concepts like "imaginary" and "hypothetical." There is no consensus on the implications of these terms in the context of fluid particles.
The discussion highlights the nuances in terminology related to abstract concepts in fluid dynamics, with participants navigating the definitions and implications of terms like "abstract," "imaginary," and "hypothetical." There are unresolved distinctions regarding these terms.
DrClaude said:A real fluid is a collection of molecules. At the macroscopic level, you describe the fluid as a continuous substance, emerging from the collective behavior of the molecules, but without treating it as made up of molecules. In other words, you zoom out and don't see individual molecules, just a continuous fluid.
When you do fluid dynamics, you need to consider an infinitesimally small volume of that fluid. But as you zoom back in, you don't come back to a molecule (you never consider the behavior of individual molecules). You simply take smaller and smaller amounts of the fluid, keeping the same properties as the bulk of the fluid.
In that sense, the fluid particle is not a real particle (i.e., a molecule), but an abstract particle that has the properties of the fluid.
If you mean "imaginary" in the sense "doesn't really exist," then yeah, sort of.mech-eng said:Then, does abstract mean here imaginary?
Merriam-Webster said:2 : expressing a quality apart from an object
DrClaude said:If you mean "imaginary" in the sense "doesn't really exist," then yeah, sort of.
But "abstract" is really the correct word:
Not at all. "Hypothetical" means that someone made a hypothesis that it might exist. Nobody is postulating that the fluid particle really exists, we know it doesn't. But we still use the concept of a fluid particle.mech-eng said:For years ago, I encountered with "hypothetical planet". Does abstract here also mean "hypothetical"?