Standard Wall Function

dinhanh · August 1, 2017, 06:33

I am having a question about the standard wall function in FLuent. The wall function in Fluent based on the Launder and Spalding wall function.

For the first node away off the wall, the production and disipation in k equation is modified based on the log law of wall. The value of epsilon is fixed.

I wonder that how the viscosity is modified base on the log law of the wall. There is no information of viscosity in Fluent. On ther other hand, The Launder - Spalding method, the wall viscosity is modified?

Thank in advance.

sbaffini · August 3, 2017, 08:36

The only reference I am aware of for Fluent wall functions is:

S.-E. Kim: A near-wall treatment using wall functions sensitized to pressure gradient

but it seems to not be available anywhere online. So, we might never know what fluent does with wall functions.

Still, modifying the turbulent viscosity is not the only possibility for implementing wall functions and, actually, it is a quite contrived one (and also bad ffrom the software engineering point of view). It is really probable that Fluent actually uses the tau_wall value directly in the boundary condition.

August 1, 2017, 06:33	Standard Wall Function	#1
dinhanh Member Anh Join Date: Sep 2014 Posts: 72 Rep Power: 12	I am having a question about the standard wall function in FLuent. The wall function in Fluent based on the Launder and Spalding wall function. For the first node away off the wall, the production and disipation in k equation is modified based on the log law of wall. The value of epsilon is fixed. I wonder that how the viscosity is modified base on the log law of the wall. There is no information of viscosity in Fluent. On ther other hand, The Launder - Spalding method, the wall viscosity is modified? Thank in advance.

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August 3, 2017, 08:36		#2
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,192 Blog Entries: 29 Rep Power: 39	The only reference I am aware of for Fluent wall functions is: S.-E. Kim: A near-wall treatment using wall functions sensitized to pressure gradient but it seems to not be available anywhere online. So, we might never know what fluent does with wall functions. Still, modifying the turbulent viscosity is not the only possibility for implementing wall functions and, actually, it is a quite contrived one (and also bad ffrom the software engineering point of view). It is really probable that Fluent actually uses the tau_wall value directly in the boundary condition.