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Reynolds Number - Numberphile

Numberphile · 560.2K views · 2019-09-04 · 16:58

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Overview

Numberphile with Tom Crawford of Oxford explains the Reynolds number, the second of three videos on Navier-Stokes and fluid flow, with demonstrations of laminar versus turbulent behavior.

On Hacker News

HN recommends it as an accessible layperson's introduction to the Reynolds number and fluid dynamics scales.

Recommended by 3 HN people across 3 months · HN mentions 2019–2021

Topics

Everyday physics & science demosRecreational & visual mathFundamental physics
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reynolds numbernavier-stokesturbulencenumberphilefluid mechanics

What people said

dagw · 2021-08 · Recommendation

When it comes to fluids (and gases) the keyword you are looking for the the Navier-Stokes equation. In most cases gases and fluids can be handled essentially the same way. There is pretty a good video introduction to Navier-Stokes here: [LINK] (part 1) and [VIDEO] (part 2) The big 'problem' with fluid dynamics is that from the equations it looks like a really simple problem. The Navier-Stokes equation is a couple of lines and you can explain it to a reasonably smart high school student who has taken calculus. And in the 'easy' case where you assume laminar flow and no turbulence it is pretty easy. The problem is when you introduce turbulence into the system then it becomes basically unsolvable and you are forced to rely on 'tricks' and approximations to make the problem computable. Most of the 'art' of CFD is picking the right tricks and approximations to solve the particular problem you have (the second 'art' is creating and a good mesh to run the solver on).

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bgilroy26 · 2020-11 · Recommendation

Thank you for writing out this comment! Even in the Age of the Internet, being able to put your hands on the right review paper is not given at all My girlfriend and I both have mental health issues and that is most of my saw in wanting to understand Neuro 101 or comparative animal neuro or Evolutionary Neuro or anything that will incrementally add to an understanding of human brains that will improve the ability to advocate for ourselves in the US health care system. Serendipitously, I was independent studying on fluid mechanics and dynamics last year[0] and had been through Purcell 1977, so I'm excited to check out your work on that account as well! [0] There are some nice YouTube videos out there to ramp you up to understanding Purcell 1977 better as a layman with undergrad maths Numberphile -- Reynolds Number [VIDEO]

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eindiran · 2019-12 · Recommendation

I think this is a good lay-person's introduction to basis of Kolmogorov's length scale, specifically the Reynold's number: [VIDEO]

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Sources

Video by Numberphile, played through YouTube.

Data and selection notes

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HN Library: HackerTube export (2026-10-31) and open-index/hacker-news. Upstream summaries and classifications may contain AI errors.

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