TURBULENCE remains one of the few unsolved problems of classical physics. Although the Navier-Stokes equation -the fundamental equation governing the flow of simple incompressible fluids - has been known since the 19th century, an understanding of even relatively simple non-steady flows still evades us. This ignorance is especially frustrating because turbulent flows are all around us in real life - on a windy day, in a river downstream from a bridge and in the swirling smoke of a bar room. The fundamental reason for this ignorance lies in the npnlinearity of the Navier-Stokes equation (and its equivalents for compressible fluids), which handicaps standard mathematical techniques for treating these problems.
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