Inertia Dominated: Explaining Physically What It Means

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High values of non-dimensional numbers like Reynolds and Weber indicate that inertial forces significantly outweigh viscous or surface tension forces in fluid dynamics. In inertia-dominated scenarios, the kinetic energy of the fluid is so substantial that other effects, such as surface tension, become negligible. This leads to behaviors where the fluid's motion is primarily driven by its inertia rather than resistance from viscosity or surface tension. There is some debate about the terminology, with concerns that "inertia dominated" may not accurately reflect the role of kinetic energy in these situations. Understanding these concepts is crucial for accurately describing fluid behavior in high-energy conditions.
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So if we have ratios like Reynolds number or Weber number, i,e ratio of inertial to viscous forces and ratio of inertial to surface tension forces respectively, I've seen many texts say that when these non-dimensional numbers are very high, the physics is "inertia dominated".

I don't really understand what this means. Can anyone explain?

As an example, for Reynolds number, we say in high Re flows, inertia dominates at the large scales and in high velocity collisions, inertia dominates the surface tension, but what, physically, does that mean?

Thanks
 
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The kinetic energy is so large that surface tension or other effects are negligible.
 
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mfb said:
The kinetic energy is so large that surface tension or other effects are negligible.

I agree, I guess my concerns are that historically we've used "inertia dominated" to describe this when in my mind it is kinetic energy, and using the word "inertia" implies something else :s
 
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