Understanding Fluid Resistance & Velocity

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Discussion Overview

The discussion revolves around the dependence of fluid resistance on velocity, specifically whether it is linear (v) or quadratic (v^2). Participants explore experimental approaches to determine this relationship and discuss theoretical implications related to fluid dynamics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether fluid resistance depends on velocity (v) or the square of velocity (v^2).
  • Another participant clarifies the inquiry, asking if the focus is on the nature of the velocity dependence or how to determine it.
  • A suggestion is made to conduct experiments using a submerged block of wood in water to measure fluid resistance, emphasizing the fun aspect of such experiments.
  • One participant hypothesizes that fluid resistance likely depends on v^1, inviting further updates on findings.
  • Another participant proposes that fluid resistance can be expressed as a power series in velocity, indicating that the linear term is the most significant contributor.
  • A later reply connects the v^2 term in turbulent flow to kinetic energy considerations, suggesting that energy principles influence the relationship between fluid resistance and velocity.

Areas of Agreement / Disagreement

Participants express differing views on the nature of fluid resistance with some suggesting linear dependence while others propose a more complex relationship involving higher-order terms. The discussion remains unresolved with multiple competing perspectives present.

Contextual Notes

Participants have not reached consensus on the specific dependence of fluid resistance on velocity, and the discussion includes various assumptions about the nature of fluid dynamics and experimental setups.

newton1
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fluid resistance

how to know the fluid resistance is depend on [tex]v[/tex] or [tex]v^2[/tex] ??
 
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Are you asking why fluid resistance is velocity dependent? Or are you asking how to determine whether the dependence goes linear or whether it goes quadratic with velocity?
 


Originally posted by Newton1
how to know the fluid resistance is depend on [tex]v[/tex] or [tex]v^2[/tex] ??

Well, you could look it up. Or you could run some experiments. A simple experiment might use a tub or water and a submerged block of wood, with a spring or rubber band providing a measurable force to move the block, and a stopwatch.

Experiments in the tub are always fun.
 
I'm going to guess it depends on [tex]v^1[/tex]... let us know when you find out. :smile:
 
It is almost certainly a power series expansion in powers of velocity, with the linear term being the most important contributor. In other words:

[itex]F(v) = a v + bv^2 + cv^4 + ...[/itex]

It would be a fun experiment to determine a, b, c,...
 
The [tex]v^2[/tex] in the formula for turbulent current is an energy thing: the kinetic energy of the fluid whirls goes with [tex]v^2[/tex], and energy equals force times deplacement.
 

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