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# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"A New Theory of Turbulence Causes a Stir Among Experts," by Barry Cipra.*Science*, 17 May 1996, page 951.

"The Wall Falls: A half-century-old equation for fluid dynamics is indoubt," by Paul Wallich. *Scientific American*, August 1996,pages 21-22.

The mathematical problem of trying to analyze and predict turbulence iscurrently beyond the scope of both theoretical and computational means. One ofthe mathematical tools that has been a mainstay in this area is "thelogarithmic law of the wall," which provides an approximate description of theshear forces that occur in turbulent flows near boundaries, such the flow ofair along an airplane wing. Now two Berkeley mathematicians, GrigoryBarenblatt and Alexandre Chorin, have come up with a theoretical approach theyclaim provides a better approximation than the logarithmic law. If correct,this work could have important implications not only for the theoretical studyof turbulence, but also for the design of such devices as high pressurepipelines. Some turbulence experts are hailing this work is an importantadvance, but others are not yet willing to foresake the logarithmic law.

*-Allyn Jackson*