Fluid Flow & Aerodynamics
why things fly, and why the usual explanation is wrong
Series

Bulk viscosity — the series

One essay so far on this idea, and more questions about it than one essay answers.
  1. The coefficient Stokes threw away is not a correction. What absorbs sound in dry air, split into the three transport effects that add to make the diffusivity of sound. Shear viscosity is the largest single contribution and it is not most of it; the bulk viscosity — which Stokes set to zero in 1845, saying in the same paper that he had no argument for doing so — is a quarter, and thermal conduction is a fifth. Setting ζ to zero does not make a small error in the absorption; it makes a 24 per cent one.

    The viscosity nobody uses

    A fluid has two viscosities. One resists a change of shape and appears in every figure on this site; the other resists a change of volume, was set to zero by Stokes in 1845 in a paper that says he had no argument for doing so, and for carbon dioxide is fifteen hundred times larger than the one everybody quotes.

    part 1 · viscous

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