how to calculate y+ in cfx?
Hi to all.I want to capture boundary layer in cfx .I have studied about solver y plus and y plus.But I could not get it properly.I want to know that how we can give y plus for BL.i.e. how to calculate that these much no of nodes will be require for capturing B.L.Which equation I should use?as far as fluent i know that that no of y+ sholud not be greater than 30 but how to do it cgf?can anybody know Please reply me thanks
 
Re: how to calculate y+ in cfx?
Hi, if you use turbulence model like kw or ke, check your res file in CFXpost, you will find a variable named y plus. that is what you want. easy. :) BTW: Y+ is less than 30...I don't think so. The wellaccepted value is Y+ < 1.0, at least < 2.0 or 3.0 something. 30 is too high for any case. I don't know why Fluent says so.

Re: how to calculate y+ in cfx?
I don't know,sorry

Re: how to calculate y+ in cfx?
Hi,
about the value of this magical y+ ... first its value can go from 0 to anything. around 1 is required for near wall models, resolving flow in a BL with many mesh points. classical wall function model for BL treatment requires y+ = 30 or more (but in some parts of a domain where BL is not important for the features one solves can run into hunderets). CFX has its own adaptive near wall treatment, which should not be much sensitive to y+ value. have a look into the theory part of the manual searching wall BC. and the last hint  do not stuck to fluent manual. I know its nicely written, but you'd better look for some CFD book like An Introduction to Computational Fluid Dynamics: The Finite Volume Method, H. K. Versteeg and W. Malalasekera, Addison Wesley Longman Limited, 1995, reprinted 1996, ISBN 0582218845 or Computational Methods for fluid dynamics Joel H. Ferziger and Milovan Peric springer verlag, 1997 corrected 2nd printing isbn 3540594345 matej 
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