wall law modifications non-newtonian fluids

C.C · January 10, 2013, 10:14

Hi all,

I have changed the standard wall function in the k-e turbulence model by UDF, but I need to confirm if it is correctly implemented and the unique way to do this is looking for the u+ profile. Someone can help me, how can I obtain u+ from Fluent? In UDF there is any pre-defined "variable" for wall shear stress or friction velocity?
I'm studying a non-Newtonian turbulent flow in a pipe. My main doubt is how Fluent treat the non-Newtonian properties (viscosity as a function of shear rate) with the turbulence. Please, if someone have any information (papers or another type of information) can help me.
Regards

sharif88 · February 23, 2014, 17:17

Hi
I am struggling to model turbulent flow of polymer solutions (dilute, power law fluids).
I have tried CFX and also FLUENT by modifying the viscosity term but I am keep getting wring results,
The most important thing for me is get the correct pressure drop and velocity profile which are coming completely wrong,
Looks like you are dealing with the same sort of simulation so I would appreciate if you help me out on this,
Thanks

C.C · February 25, 2014, 05:48

Hi!

In my case, I modified the viscosity as a function of shear rate and also the wall functions in Fluent using an UDF... The velocity profile is more similar with the experimental result with this modifications. In the pulp case as in the polymer cases the pressure drop is lower than the water pressure drop in the same conditions. By modifying the viscosity and the wall function I get lower pressure drop but not yet similar to the experimental result.
Regards

January 10, 2013, 10:14	wall law modifications non-newtonian fluids	#1
C.C Member CC Join Date: Jun 2011 Posts: 73 Rep Power: 16	Hi all, I have changed the standard wall function in the k-e turbulence model by UDF, but I need to confirm if it is correctly implemented and the unique way to do this is looking for the u+ profile. Someone can help me, how can I obtain u+ from Fluent? In UDF there is any pre-defined "variable" for wall shear stress or friction velocity? I'm studying a non-Newtonian turbulent flow in a pipe. My main doubt is how Fluent treat the non-Newtonian properties (viscosity as a function of shear rate) with the turbulence. Please, if someone have any information (papers or another type of information) can help me. Regards Abhi.shek likes this.

February 23, 2014, 17:17		#2
sharif88 New Member Majid Join Date: Jan 2014 Location: Canada Posts: 23 Rep Power: 13	Hi I am struggling to model turbulent flow of polymer solutions (dilute, power law fluids). I have tried CFX and also FLUENT by modifying the viscosity term but I am keep getting wring results, The most important thing for me is get the correct pressure drop and velocity profile which are coming completely wrong, Looks like you are dealing with the same sort of simulation so I would appreciate if you help me out on this, Thanks Abhi.shek likes this.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Law of the wall in the presence of pressure gradient	yidongxia	Main CFD Forum	2	August 5, 2012 15:40
UDF for wall slipping	HFLUENT	Fluent UDF and Scheme Programming	0	April 27, 2011 13:03
Star CCM+ issue (VOF and Non newtonian power law)	Sam	Siemens	3	January 23, 2009 08:39
Multicomponent fluid	Andrea	CFX	2	October 11, 2004 06:12
wall in fluids flow.	Andrew Garrard	FLUENT	3	January 23, 2004 03:13

February 25, 2014, 05:48		#3
C.C Member CC Join Date: Jun 2011 Posts: 73 Rep Power: 16	Hi! In my case, I modified the viscosity as a function of shear rate and also the wall functions in Fluent using an UDF... The velocity profile is more similar with the experimental result with this modifications. In the pulp case as in the polymer cases the pressure drop is lower than the water pressure drop in the same conditions. By modifying the viscosity and the wall function I get lower pressure drop but not yet similar to the experimental result. Regards