# Non-Newtonian Flow: Power law (2D BFS)

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 1, 2009, 08:36 Non-Newtonian Flow: Power law (2D BFS) #1 New Member   Harsh Chaudhary Join Date: Apr 2009 Posts: 2 Rep Power: 0 Hi everyone, I am a student at IIT Roorkee in India. I am trying to stimulate 2-Dimensional non-Newtonian flow over a backward facing step. I'm using power law model. But I am not getting the correct results. (Interestingly the values of the recirculation length for a particular Re (say 100) match with the value given for twice the value of Re (Here 200) in my reference paper ) The same mesh is generating very good results for Newtonian flow. Re: 50 to 400. n=0.25 Inlet Vel: 2 Inlet Temp: 275k Density and consistency index are manipulated to give Re the desired value. Min Viscosity= e(-10) Max Viscosity= e(+10) Ref Temp= 0 k (This was 273 earlier , no difference occurred) Pressure-Velocity coupling: SIMPLE Discretization> Pressure: Standard Momentum: Power Law Energy: Power Law Please if anyone can spot any problem in these values do inform me. Also if you happen to have some study material\Fluent tutorials related to non-Newtonian flow/Backward Facing step/Power Law or Heat transfer for laminar flow in fluent, please do forward it to me. Any kind of suggestion/guidance will be highly appreciated. Thanks.

April 5, 2009, 13:49
#2
New Member

Join Date: Mar 2009
Posts: 23
Rep Power: 10
Quote:
 Originally Posted by hellouch Hi everyone, I am a student at IIT Roorkee in India. I am trying to stimulate 2-Dimensional non-Newtonian flow over a backward facing step. I'm using power law model. But I am not getting the correct results. (Interestingly the values of the recirculation length for a particular Re (say 100) match with the value given for twice the value of Re (Here 200) in my reference paper ) The same mesh is generating very good results for Newtonian flow. Re: 50 to 400. n=0.25 Inlet Vel: 2 Inlet Temp: 275k Density and consistency index are manipulated to give Re the desired value. Min Viscosity= e(-10) Max Viscosity= e(+10) Ref Temp= 0 k (This was 273 earlier , no difference occurred) Pressure-Velocity coupling: SIMPLE Discretization> Pressure: Standard Momentum: Power Law Energy: Power Law Please if anyone can spot any problem in these values do inform me. Also if you happen to have some study material\Fluent tutorials related to non-Newtonian flow/Backward Facing step/Power Law or Heat transfer for laminar flow in fluent, please do forward it to me. Any kind of suggestion/guidance will be highly appreciated. Thanks.
Dear Mr. Harsh Chaudhary
AND send me your using Re equation
With best regards

 April 6, 2009, 00:44 #3 New Member   Harsh Chaudhary Join Date: Apr 2009 Posts: 2 Rep Power: 0 The dimensions of the (2D) grid are : upstream 1hX15h downstream 2hX30h here h is the upstream inlet breadth So the step height is 1h. Re= (2h)^n (u)^(2-n) ρ / μ u: inlet velocity (uniform at inlet) n= 0.25 (for validation with ref) rest information is given in my prev post. My reference is a paper by Choi et al. "Numerical study of the impact of non-Newtonian blood behavior on flow over a two-dimensional backward facing step" Biorheology 42 (2005) 493–509 They have taken blood as the reference fluid and used the Carreau model for non-Newtonian flow. I was trying to use power fluid model to regenerate results close to this. I also tried using Carreau model but again the results didn't match. Some of my results: Re=100 Choi (Xr/s) : 2.8 Our result (carreau) (Xr/s): 1.938 Our result (Power law)(Xr/s): 4.82 Re=200 Choi (Xr/s) : 4.8 Our result (carreau) (Xr/s) : 3.877 Our result (Power law)(Xr/s): 8.6 Xr : Reattachment length from step Please do help me out if you find something wrong in this.... Thanks a LOT!

April 21, 2009, 03:03
#4
New Member

Join Date: Mar 2009
Posts: 23
Rep Power: 10
Quote:
 Originally Posted by hellouch The dimensions of the (2D) grid are : upstream 1hX15h downstream 2hX30h here h is the upstream inlet breadth So the step height is 1h. Re= (2h)^n (u)^(2-n) ρ / μ u: inlet velocity (uniform at inlet) n= 0.25 (for validation with ref) rest information is given in my prev post. My reference is a paper by Choi et al. "Numerical study of the impact of non-Newtonian blood behavior on flow over a two-dimensional backward facing step" Biorheology 42 (2005) 493–509 They have taken blood as the reference fluid and used the Carreau model for non-Newtonian flow. I was trying to use power fluid model to regenerate results close to this. I also tried using Carreau model but again the results didn't match. Some of my results: Re=100 Choi (Xr/s) : 2.8 Our result (carreau) (Xr/s): 1.938 Our result (Power law)(Xr/s): 4.82 Re=200 Choi (Xr/s) : 4.8 Our result (carreau) (Xr/s) : 3.877 Our result (Power law)(Xr/s): 8.6 Xr : Reattachment length from step Please do help me out if you find something wrong in this.... Thanks a LOT!
Dear Mr. Hellouch
Iam very sorry to late for reply quickly, I run your case and i have same your result.

Sorry
Many thanks

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post kevin FLUENT 8 August 11, 2015 13:00 cpplabs OpenFOAM Running, Solving & CFD 1 February 13, 2008 09:09 diaw Main CFD Forum 104 February 16, 2006 06:44 Atit Koonsrisuk CFX 0 February 23, 2005 13:44 Tylor Xie Main CFD Forum 0 June 9, 1999 07:33

All times are GMT -4. The time now is 18:01.