# Prandtl mixing length vs Isotropic assumption

 Register Blogs Members List Search Today's Posts Mark Forums Read

 March 23, 2000, 23:53 Prandtl mixing length vs Isotropic assumption #1 Mohammad Kermani Guest   Posts: n/a Hi: In Prandtl mixing length hypothesis, which is almsot the background of all zero equation models, the turbulent fluctuataions throughout the whole computational domain are modeled as: u' =. v' =. l*du/dy (=. is appoximation sign) But ( u' =. v' ) is exactly the definition of isotropic turbulent. My question: Does not this a violate the anisotropicicity fact of the turbulent close to the wall? i.e. how the Prandtl mixing length hypothesis justifies the anisotropic turbulent close to the wall? Thanks for your comment. MJ

 March 26, 2000, 15:47 Re: Prandtl mixing length vs Isotropic assumption #2 Bob Anderson Guest   Posts: n/a If this were true, and the only weakness of the mixing length hypothesis, it would be doing pretty well. The mixing length hypothesis is not meant to be any sort of rigorous derivation by any means. That being said, I think the development is only contingent upon \overline{u'} and \overline{v'} being related by a constant. That constant doesn't have to be particularly small. In fact, it doesn't even have to be constant, since the mixing length is a function of y. You could split off any portion of the y dependence in l and consider it to be part of the relationship between u' and v' if you like. Bob

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post david39 OpenFOAM Running, Solving & CFD 6 February 2, 2011 04:01 eva Main CFD Forum 1 February 27, 2009 15:19 sarah_ron FLUENT 0 November 28, 2004 00:29 mukkarum Main CFD Forum 4 July 25, 2002 05:16 Mohammad Kermani Main CFD Forum 0 March 24, 2000 00:06

All times are GMT -4. The time now is 16:01.