Rate of flow, or velocity of fluid?

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SUMMARY

The discussion centers on the distinction between "rate of flow" and "velocity of fluid" in the context of fluid dynamics. Participants clarify that "rate of flow" typically refers to the total volume passing a point per unit time, while "velocity" pertains to the speed of the fluid. The continuity equation, expressed as cross-sectional area multiplied by velocity equals a constant, is emphasized as a fundamental principle that governs these relationships. The ambiguity of terms used by authors in fluid mechanics can lead to confusion regarding these concepts.

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Doug1943
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I was looking at a site which described the classic demonstration to illustrate how water pressure increases with depth (shown by punching three holes, one above the other separated by a few centimeters, in a container of water): "The smaller the holes, the greater the rate of flow from the holes."

Is this right? Does not the author mean, "The smaller the holes, the greater the velocity of the water"? (I think of "rate of flow" as being total volume passing a point per unit time, which must remain constant. And presumably these relationships only hold when the flow is laminar and frictional forces are neglected?)
 
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I believe you are correct, the author meant velocity. Otherwise the continuity equation would be violated.

cross sectional area x velocity = constant
 
It depends on what the author said. If he/she just said "flow rate" or "rate of flow", those are ambiguous terms and so they may have simply meant velocity rather than volumetric flow rate or mass flow rate. In other words, they may have been right or wrong but you can't really tell because the terminology as you describe it is ambiguous.
 
If the holes are equal in size, then different flow velocity necessarily means different mass/volumetric flow, for liquids.
 

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