CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Multiphase flow of Nanofluids - Low Nusselt number problem

Register Blogs Community New Posts Updated Threads Search

Like Tree1Likes
  • 1 Post By ios

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 30, 2015, 03:20
Smile Multiphase flow of Nanofluids - Low Nusselt number problem
  #1
New Member
 
Aarthy Meena's Avatar
 
Aarthy Meena
Join Date: Oct 2015
Location: Trichy
Posts: 29
Rep Power: 11
Aarthy Meena is on a distinguished road
Hello Everyone,

Am Aarthy, I am new to FLUENT.

I am modelling 2-D flow and heat transfer of nanofluids around an unconfined square cylinder for my M.Tech project. Initially, I tried a single phase flow using effective property models for properties of nanofluids. Those simualtions are fine and gave comparable results with the literature.

Now, I am trying to use multi-phase flow model. I am trying with mixture model in FLUENT. I tried with particle volume fraction as 0 (i.e., pure basefluid), and I got good values of Nu and drag coefficients which matched with literature.

When I increased the particle volume fraction, the values of Nu and C_D decreased. But, it is well known that, when particle volume fraction is increased, C_D and Nu will increase.

So I am stuck with this. Kindly, pls help me very urgent....
Aarthy Meena is offline   Reply With Quote

Old   November 5, 2015, 02:30
Default
  #2
ios
New Member
 
srt
Join Date: May 2013
Posts: 5
Rep Power: 13
ios is on a distinguished road
Hi Aarthy,

Firstly have you ever tried to monitor the conductivity values ? The mixture model defines the conductivity (k) with simple averaging (i.e. kmix=kf(1-phi)+phi*kp). For instance lets assume you are using Al2O3 nano particles with k~35 W/mK so the conductivity of Al2O3/water nanofluid with 0.01 volume fraction will be ~0.9-1.06 depending on temperature which is very high. Hence the Nu number will be decreased rapidly.
You can implement different conductivity model into Fluent by using UDF or manually or you can use different two-phase models. The thing is it is hard to define the proper thermal properties with mixture model. Also even if you manage to do it it won’t be so different than the single phase approach because of the small drift velocities between phases.
Anyways, good luck.

Last edited by ios; November 9, 2015 at 05:18.
ios is offline   Reply With Quote

Old   November 17, 2015, 06:01
Default Thank You
  #3
New Member
 
Aarthy Meena's Avatar
 
Aarthy Meena
Join Date: Oct 2015
Location: Trichy
Posts: 29
Rep Power: 11
Aarthy Meena is on a distinguished road
Thank you ios... Thank you for your elaborate reply.. Can you pls help me by saying the step by step procedure of Eulerian-Eulerian method for my problem.. I will be very grateful to you.... You can contact me at aarthychubby123@gmail.com
__________________
Aarthy,
PG Student,
National Institute of Technology, Trichy, India.
Aarthy Meena is offline   Reply With Quote

Old   January 6, 2016, 12:40
Default
  #4
New Member
 
Aarthy Meena's Avatar
 
Aarthy Meena
Join Date: Oct 2015
Location: Trichy
Posts: 29
Rep Power: 11
Aarthy Meena is on a distinguished road
Hi ios,

I tried as per ur suggestion. But I observe a decrease in drag and mean Nusselt number with increase in particle volume fraction. This is contradicting with literature.

Thank You.
__________________
Aarthy,
PG Student,
National Institute of Technology, Trichy, India.
Aarthy Meena is offline   Reply With Quote

Old   January 6, 2016, 12:59
Default
  #5
ios
New Member
 
srt
Join Date: May 2013
Posts: 5
Rep Power: 13
ios is on a distinguished road
Firstly stop contradicting with yourself then you can go for literature.
Attached Images
File Type: png Screenshot_2016-01-06-18-49-59.png (157.8 KB, 53 views)
rajann_786 likes this.
ios is offline   Reply With Quote

Old   January 6, 2016, 13:03
Default
  #6
New Member
 
Aarthy Meena's Avatar
 
Aarthy Meena
Join Date: Oct 2015
Location: Trichy
Posts: 29
Rep Power: 11
Aarthy Meena is on a distinguished road
Quote:
Originally Posted by ios View Post
Firstly stop contradicting with yourself then you can go for literature.

I have mentioned that I have some doubts in the results.
You can see in the image which you have attached.
Those doubts are I observe increase in CD and NUM at lower Reynolds numbers. At higher Reynolds numbers I observed an opposite behavior. That is why I have posted now.
__________________
Aarthy,
PG Student,
National Institute of Technology, Trichy, India.
Aarthy Meena is offline   Reply With Quote

Reply

Tags
fluent, multiphase flows, nanofluids, nusselt number


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 Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[mesh manipulation] Mesh Refinement Luiz Eduardo Bittencourt Sampaio (Sampaio) OpenFOAM Meshing & Mesh Conversion 42 January 8, 2017 13:55
decomposePar -allRegions stru OpenFOAM Pre-Processing 2 August 25, 2015 04:58
Nusselt Number problem A7A FLUENT 1 May 24, 2015 13:17
SigFpe when running ANY application in parallel Pj. OpenFOAM Running, Solving & CFD 3 April 23, 2015 15:53
there is a problem with fully developed Nusselt number eeman Fluent UDF and Scheme Programming 4 September 24, 2012 02:36


All times are GMT -4. The time now is 02:57.