turbulence production

wilson · December 16, 2009, 13:42

Can anyone explain the mechanisms of turbulence production in terms of the Reynolds Averaged Navier Stokes equations?

Thanks

ghorrocks · December 16, 2009, 16:47

I won't even start on that one. Visit your local university library and get a turbulence textbook.

Josh · December 16, 2009, 18:50

^LOL. Glenn's right. There are full courses dedicated to that topic alone.

The absolute very basic definition is that everything is based on an average value plus a fluctuation (e.g. from the Navier-Stokes equations, u becomes u_avg + u', where u' is the fluctuation in u). The average of the fluctuations is zero. When these terms are substituted into the N-S equations and the N-S equations are averaged, the fluctuation averages disappear (since they are zero). You end up with essentially the N-S equations, but replace each value with the average value (e.g. u becomes u_avg). Also, you end up with an extra term since the average of a product is not the product of an average (e.g. (density x u)_avg does not equal density_avg x u_avg).

Anyway, that's just the tip of the iceberg. Follow Glenn's suggestions.

December 16, 2009, 13:42	turbulence production	#1
wilson New Member Mike Join Date: Dec 2009 Posts: 14 Rep Power: 16	Can anyone explain the mechanisms of turbulence production in terms of the Reynolds Averaged Navier Stokes equations? Thanks

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December 16, 2009, 16:47		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	I won't even start on that one. Visit your local university library and get a turbulence textbook.

December 16, 2009, 18:50		#3
Josh Senior Member Joshua Counsil Join Date: Jul 2009 Location: Halifax, Nova Scotia, Canada Posts: 366 Rep Power: 17	^LOL. Glenn's right. There are full courses dedicated to that topic alone. The absolute very basic definition is that everything is based on an average value plus a fluctuation (e.g. from the Navier-Stokes equations, u becomes u_avg + u', where u' is the fluctuation in u). The average of the fluctuations is zero. When these terms are substituted into the N-S equations and the N-S equations are averaged, the fluctuation averages disappear (since they are zero). You end up with essentially the N-S equations, but replace each value with the average value (e.g. u becomes u_avg). Also, you end up with an extra term since the average of a product is not the product of an average (e.g. (density x u)_avg does not equal density_avg x u_avg). Anyway, that's just the tip of the iceberg. Follow Glenn's suggestions.