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For flow in a smooth tube, which Reynolds number is clearly in the turbulent range?

A Reynolds number above about 3000 indicates turbulent flow.

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  1. 4000 ✔
  2. 1000
  3. 200

Why: Reynolds number compares inertial effects with viscous effects. OpenStax gives tube flow below about 2000 as laminar, above about 3000 as turbulent, and the interval between as unstable.

Huh, didn't know that: Reynolds number is dimensionless, so it helps compare dynamically similar flows at different sizes and speeds.

The dad joke
Reynolds counted the swirls because turbulence had no orderly queue.
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References

Answer: 4000. Reynolds number compares inertial effects with viscous effects. OpenStax gives tube flow below about 2000 as laminar, above about 3000 as turbulent, and the interval between as unstable.

  1. OpenStax University Physics Volume 1, Viscosity and Turbulence openstax.org/books/university-physics-volume-1/pages/14-7-viscosity-and-turbulence
    For Reynolds number below about 2000, flow is laminar. For Reynolds number above about 3000, flow is turbulent.
    Checked 2026-10-10.

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