# 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: 13
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: 13
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