how to deal with the wall boundary of les?

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 June 11, 2006, 19:20 how to deal with the wall boundary of les? #1 mud2003 Guest   Posts: n/a Ask for help! In the les turbulent model, how to deal with the wall boundary? And if the y+ is needed , how to calculate it?

 June 12, 2006, 13:17 Re: how to deal with the wall boundary of les? #2 agg Guest   Posts: n/a In the boundary layer, you must use DNS resolution, in other words, y+ < 1. (see any standard book on turbulence for y+ calculation) Wall models are an alternative, and you might want to try them.

 June 13, 2006, 06:21 Re: how to deal with the wall boundary of les? #3 mud2003 Guest   Posts: n/a agg, can talk about the calculation of y+ in les ? The y+ fomulation need k, but how to get it in les??

 June 15, 2006, 09:29 Re: how to deal with the wall boundary of les? #4 agg Guest   Posts: n/a y+ is just a non-dimensional distance based on friction velocity y+ = y*utau/viscosity utau = (wall shear stress/density)^0.5 You can calculate wall shear stress from LES using velocity gradient at the wall and hence y+

 June 17, 2006, 13:38 Re: how to deal with the wall boundary of les? #5 mud2003 Guest   Posts: n/a agg, you mean the wall shear stress can get by using velocity gradient at the wall, so must use DNS resolution, in other words, y+ < 1??? But when the y+>30, the wall shear stress is diff to get?

 June 18, 2006, 18:39 Re: how to deal with the wall boundary of les? #6 agg Guest   Posts: n/a When y+ is not resolved, you can use wall models. An example would be to use: 1) u+ = y+ in the viscous sublayer (if y+ <= 10) 2) u+ = 2.5 ln(y+) + 5.5 (if 10 < y+ <= 300) For (2), an iterative procesure is required, since wall stress is an unknown in both LHS and RHS. Once u+ is known, you can back calculate u at that point. Best information can be found in papers. You should be able to find papers with LES using wall models.

 June 18, 2006, 19:19 Re: how to deal with the wall boundary of les? #7 Halim Guest   Posts: n/a Visit here http://www.lstm.uni-erlangen.de/~breuer/ and see this CFD - Code LESOCC (Large Eddy Simulation on Curvilinear Coordinates) Numerical Method Discretization Subgrid Scale Model === Wall Boundary Conditions === Good Luck! Halim

 June 20, 2006, 11:42 Re: how to deal with the wall boundary of les? #8 mud2003 Guest   Posts: n/a i am reading, thanks halim!

 June 27, 2006, 05:36 Re: how to deal with the wall boundary of les? #9 aiya Guest   Posts: n/a hi....halim the Code LESOCC is shared? where can get some code for learning?

 June 27, 2006, 18:21 Re: how to deal with the wall boundary of les? #10 Halim Guest   Posts: n/a (1) Ask to Dr. Breuer (E-mail: breuer_at_lstm.uni-erlangen.de ) (2) Sorry, I do not know. I know that if you buy this book, you can have a source code for LES. "Fluid Flow Phenomena : A Numerical Toolkit" by Paolo Orlandi, Kluwer Academic Publishers, 2000. Halim

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