Hi
in ansys fluent's dacuments it has been said that : (( ANSYS Fluent has taken steps to offer more advanced wall formulations, which
allow a consistent mesh refinement without a deterioration of the results. Such -independent formulations are the default for
all omega-equation-based turbulence models. For the epsilon-equation-based models, the Menter-Lechner and Enhanced Wall Treatment (EWT)
serve the same purpose. A -insensitive wall treatment is also the default for the Spalart-Allmaras model and allows you to run this model
independent of the near-wall resolution. ))
so, is it true that for models mentioned above like k-omega or k-epsilon(EWT,Menter-lechner)there is no need to check y+ value to be in a certain range ?
for example can i use k-epsilon model with enhanced wall treatment and y+ value changes between 0.5 to 600 ?
if my assumption is'nt true , what is the certain range of y+ value for all turbulence models like k-epsilon with wall functions or k-omega
without wall functions ? please give me a reliable source ...
thanks...
as said in this file Fluent-Intro_15.0_L07_Turbulence.pdf that sent by dear panayamplilly
if I use wall functions then y+ should between 30 and 300, so what this Sentences mean = ( For the epsilon-equation-based models, the Menter-Lechner and Enhanced Wall Treatment (EWT)serve the same purpose. A -insensitive wall treatment is also the default for the Spalart-Allmaras model and allows you to run this model independent of the near-wall resolution)?
is this mean that if we use enhanced wall treatment then there is no need to check the y+ value ?
http://www.cfd-online.com/Forums/cfx/26941-yplus-value-sst.html
for structure mesh the meshing quality for SST model is 1 to 5 and for K epsilon the value is below 30. for unstructured mesh the value of y+ should be below one.
For accurate wall shear stress, the SST turbulence model must below 5. Also, I will suggest you that study these models in Versteege's book of fluid dynamics. All these models are given in detail in this book
The full name of the book is " An Introduction to Computational Fluid Dynamics" by H K Versteeg and W Malalasekera
Dear Amir,
It depends on many factors and first, you need to consider the boundary layer thickness, buffer layer thickness, and start applying y plus later on. By the way, the point is here your bluff body shape and as you certainly know the same value for y plus could not be employed for all regions equally. You may need to decrease y plus for shape edges or location where are normally prone to flow separation from the surface. for more information I recommend you to see Dr. Mounesan lessons on kashti.ir which would be comprehensive and extremely helpful.
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