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The Key to Countering Turbulence: More Turbulence

Via today’s New York Times:

At relatively slow rates of flow, turbulence is intermittent — it’s pushed along, Dr. Hof said, by smooth-flowing fluid behind it. By studying flows in a special glass pipe and modeling them on a computer, Dr. Hof and his colleagues realized that introducing an eddy into this smooth-flowing zone would eliminate the turbulence in front of it. “One turbulent eddy kills the other,” he said. As long as the pipe is straight, the flow should then remain smooth.

One wonders about any potential analogies to traffic here — the not quite perfect comparison that springs to my mind is the work, via people like Dirk Helbing and Serge Hoogendoorn, that shows in pedestrian escape modeling that introducing an obstacle into an exit opening actually improves the rate of discharge.

Any hardcore flow/sim types have any thoughts?

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This entry was posted on Tuesday, March 23rd, 2010 at 10:58 am and is filed under Traffic Engineering. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

3 Responses to “The Key to Countering Turbulence: More Turbulence”

  1. Mike Chalkley Says:
    March 24th, 2010 at 3:31 am

    Tom, not completely on topic here but relevant to the issues you deal with… Have you read ‘Death on the Streets’ by Robert Davis (isbn 0-948135-46-8)? A fascinating essay on how cars & roads in the UK have contributed to a lot of the social and safety problems we now face.

    One of his central points is that the seat belt laws here have resulted in drivers ‘risk-compensating’ by driving faster instead of safer. This results in no net safety benefit for car occupants and hugely increased risk to vulnerable road users.

    I couldn’t remember if you’d mentioned his work in Traffic (I’ve lent it to my neighbour - a local council traffic planner - so I can’t check!). If you haven’t read it - DO! It’s an eye opener and poses the worrying point that if we don’t do something drastic about cars like making them fully automatic, we will continue to suffer from the carnage and car-centricity we currently have on the roads.

  2. Sandeep Says:
    March 28th, 2010 at 8:06 am

    Tom, your blog has many interesting things and I keep reading it from time to time.
    About this post, the research on Dr. Hof says,
    “…it’s pushed along by smooth-flowing fluid behind it…”
    “…Dr. Hof and his colleagues realized that introducing an eddy into this smooth-flowing zone would eliminate the turbulence in front of it…”
    Vehicular traffic flow is likened and sometimes modeled using some principles from gas flow. But the key difference is that traffic flow is anisotropic i.e. a vehicle does not respond to conditions behind it but only in front of it. Imagine a congested stretch of a roadway. Now if there is a free flowing traffic behind it, what would you expect ? The vehicles in the smooth will also enter the congested regime unlike a gas flow where the flow from behind pushes the gas in front of it.
    Thanks for posting though :)

  3. Sandeep Says:
    March 28th, 2010 at 8:10 am

    Although pedestrian traffic is slightly different, I’d expect the same as vehicular traffic or even worse, a stampede :P

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Traffic Tom Vanderbilt

How We Drive is the companion blog to Tom Vanderbilt’s New York Times bestselling book, Traffic: Why We Drive the Way We Do (and What It Says About Us), published by Alfred A. Knopf in the U.S. and Canada, Penguin in the U.K, and in languages other than English by a number of other fine publishers worldwide.

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