Enhanced Wall Treatment
Enhanced Wall Treatment is using by default for kw SST model.
What is it  Enhanced Wall Treatment? It's a kind of wall function, or some blended condition, that models boundary layer directly on meshes with y+=1 and uses some wall function, when y+>30. If it's so what kind of wall function uses Enhanced Wall Treatment? 
So if it's no separation and u+ calculated by single equation in all cases is there specific requirements for grid resolution in a near wall zone for proper using Enhanced Wall Treatment?

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That is only for velocity (u+). You will have to dig up the ones for the turbulence quantities.
The Fluent manual goes into detail the EWT for the kepsilon models but leaves out a lot of details for the kwSST model. But you can find them on the CFDonline wiki section. 
Hi paduchev,
you can find some additional information here: http://hpce.iitm.ac.in/website//Manu...ug/node514.htm 
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Hmmm, they should be the same, but you have a point. You should use the newest manual of fluent 13, of course.

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http://www.cfdonline.com/Wiki/Nearwall_treatment_for_komega_models 
Thanks a lot

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If this is true then they would have used the simple elseif command which was used in the previous version of SA and KOmega model. Still you can observe in the theory guide of Fluent (I am talking about SA model) they are using the integration to wall approach for the Y+< 2 and wall function approach for the Y+>30 and strongly recommend to make the meshes either with Y+< 2 or Y+> 30 so that they can use the either IWT or wall function approach. Although the actual switch is implemented at the intersection of two profiles i.e. 11.225 (previously it was implemented at 11.06 in version 6.3). Now lets discuss the theory behind the enhanced wall treatment for Kepsilon and Komega models. First question comes into mind why two approaches used for the same effect i.e. implementing the smooth transition between the loglaw and viscous sublayer implementation. This is because: 1. Kepsilon models were not designed for the near wall flow, therefore they require the damping functions to simulate the near wall effects. 2. Komega based models were designed originally for the near wall region and therefore does not require the damping functions, hence the hybrid wall functions (blending of near wall and log law function) were implemented directly and same is true for SA model. You can find the details of latest work here for the komega and SA model with hybrid wall functions here http://num.math.unigoettingen.de/ba...ings/knopp.pdf http://num.math.unigoettingen.de/ba...ngs/alrutz.pdf But whether it is two layer approach (Kepsilon) or single model implementation approach (Komega or SA model) the purpose is same i.e. to remove the short comings of the both models. i.e. the low reynolds number is valid for the Y+ < 0.2 (low reynolds number Kepsilon model) or Y+<2 (Komega model, I am not writing low reynolds number komega becuase Komega is originally a low Reynolds number model, so no need to define the Rose) and similarly the Y+ > 30 for high Reynolds number Komega and KEpsilon model. To be continued.... Now consider this http://en.wikipedia.org/wiki/Law_of_the_wall It is clearly written that U+ = Y+ for the Y+ < 5 (you can consider the sublayer up 11.225 but at the Y+ = 12 the error is around 25%) http://en.wikipedia.org/wiki/Law_of_the_wall Log law is for Y+> 30. Buffer zone is Y+ = 5 to Y+ = 30 This is problem area where both models (low Reynolds number and high Reynolds number ) don't work. This is the reason why the hybrid or enhanced wall treatment model was came into existence. Here is the some material from Fluent user guide: Quote:
"The Velocity and Temperature Distribution of OneDimensional Flow with Turbulence Augmentation and Pressure Gradient. Int. J. Heat Mass Transfer, 12:301318, 1969." Put in simple words: 1. With Y+~1 , you are solving the low Reynolds number Kepsilon model 2. In original form Wolfstein model is not applicable for the Y+ > 0.2 3. So to over come this we have to use the hybrid wall functions. 4. Enhanced wall treatment is method to implement the hybrid (or enhanced) wall functions for the varying Y+ in the CFD model. 5. Enhanced wall treatment is not needed to implement hybrid (enhanced) wall functions in komega model because they are already applicable upto viscous sublayer. Now the question is how does the enhanced (hybrid) wall function work. They work like Uplus = (1blending function) * Uplus (of viscous sublayer) + blending function * Uplus (of log law) Blending function = 0 for y+ < 6 Blending function =~ 1 for Y+ > 3040 So for Y+< 6 you have viscous sub layer and you are using the low Reynolds number model for Y+> 30 You are using the log law implement ion (aka wall functions) Between Y+ ~ 6 and 30 one is using the linear some of both profiles according to the relative weightage. For example in reference http://num.math.unigoettingen.de/ba...ings/knopp.pdf Blending functions has the following values (Equation 7 of reference http://num.math.unigoettingen.de/ba...ings/knopp.pdf) Y+ = 1 , BF = 0 Y+ = 10, BF = 0.018 Y+ = 12, BF = 0.038 Y+ = 15, BF = 0.094 Y+ = 20, BF = 0.2922 Y+ = 25, BF = 0.626 Y+ = 27, BF = 0.761 Y+ = 30 , BF = 0.909 Y+ = 35, BF = 0.9929 Y+ = 38, BF = 0.9992 Y+ = 40, BF = 0.9998 Blending function is different for different terms. For example in above example, BF was calculated for U+ and Y+. But which ever function is used the basic theory is same. PS : I have already mentioned in one thread that the enhanced wall treatment is good for the Y+ < 10, because for higher values you have increasing weitage of log law and which is not good at predicting the separation. 
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Enhanced wall treatment is method to implement the enhanced wall function for the two layer model like Kepsilon model. It uses the normal viscous sub layer (Y+= 15) and log law formulae (wall function with Y+ >30). Only difference is that it uses the blending function to make it useful in the region Y+ from 530 (buffer zone). 
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Hi,
i am modelling a turbulent flow in a finned tube. I am very interested in the near wall behaviour and my aim is to get values for pressure drop and the surface heat transfer coefficient. I am using the kw SST model. As far as i understand this model it combines the advantages of the kE model for fully turbulent flow far away from the wall and the kw modell near the wall. As proposed in the fluent 13.0 tutorial 6 for turbulence modelling i set my y+ value to y+=0,25 and i meshed a boundary layer with 15 cells for the inner region flow which is governed by viscous effects. so my questions are: 1. can i enable the "low Re corrction"? the kw model does already solve the flow close to the wall? 2. what does the "viscous heating" mean? thanks 
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Is the Enhanced wall treatment of Fluent use the same idea as the CFX's Automatic wall treatment? Do they have any difference besides the coefficient values? 
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In the case of the komega and sa model family we dont need special treatment for the boundary layer modelling as these models are valid upto viscous sublayer. So AWT is the method to ease the restrictions of yplus on the IWT approach with the almost same results and reliability. 
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Thank you very much for your clarifying posts. I wish the ansys fluent manual was so clear. Can you please justify your assertion (see quote) by providing a reference or something that can be cited within an article? 
enhanced wall function
hey
iam modeling an ejector with RNG kepsilon turbulence viscosity..i used enhanced wall function and then selected the pressure gradient effect but somehow when iam solving the problem the iterating stops with an error says float invalid number...then when i unselect the pressure gradient it works just fine...but i need that pressure gradient for my job.can anyone help??....thanks bro;) 
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