|
[Sponsors] |
Low Reynolds K Epsilon Launder Sharma Model Functions Doubt... |
![]() |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
![]() |
![]() |
#1 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Hi folks,
I am trying to implement the Low Reynolds K Epsilon Launder Sharma Turbulence Model in 3D from scratch because I will need to some changes later on to implement two phase modeling. However I have some doubts about the E and D model functions, as seen in the wiki section: http://www.cfd-online.com/Wiki/Low-Re_k-epsilon_models. I am unsure if these functions only apply to the YY axis, or do I need to use a gradient for them?? For D the gradient is pretty straightforward, but for E I am struggling a bit? Do I have 3 or 6 terms for the gradient, because the partial derivatives change depending on which axis you differentiate first... ![]() ![]() Hope it's clear and someone can help.. Cheers! Rui |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Administrator
|
y in those formulas refers to the direction normal to the wall. Hence, in a 3D code it will be dependent on how the wall is oriented and will be a combination of x,y and z.
|
|
![]() |
![]() |
![]() |
![]() |
#3 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Thank you for your reply jola!
![]() Could you suggest some articles or thesis or anyother source that has those equation so that I can better understand? Cheers! Rui |
|
![]() |
![]() |
![]() |
![]() |
#4 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Also, regarding the extra source terms:
for two dimensional pipe flow and assuming flow in the x-direction, the normal is y. However, in 3D and pipe flow in the z-direction, both x and y are normal to the flow. I am not quite understanding how to combine the three coordinates in the extra source terms. Could you please provide some more details. Thank you. Best Regards, Rui |
|
![]() |
![]() |
![]() |
![]() |
#5 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
I guess I have some progress...
So, I believe that for 3D the extra source term: ![]() ![]() ![]() + ![]() ![]() ![]() Is this a correct assumption? I think it's a bit long when compared with the two dimensional case, however it seems logical when I look at the general expression: ![]() I wonder if it's correct for the 3D case... ![]() Can anyone provide some input? Best Regards, Rui |
|
![]() |
![]() |
![]() |
![]() |
#6 |
Senior Member
Join Date: May 2011
Posts: 231
Rep Power: 17 ![]() |
hi Rui,
Did you manage to apple the model in two phase model? Quote:
|
|
![]() |
![]() |
![]() |
![]() |
#7 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Hello Kanarya,
yes I was. I am using it now in my simulations. How can I help you? Best Regards, Rui |
|
![]() |
![]() |
![]() |
![]() |
#8 | |
Senior Member
Join Date: May 2011
Posts: 231
Rep Power: 17 ![]() |
Hi Rui,
do you have already publish some results? Or do you have some comparison with the classical methods with wall function! I already did it for single case but I have some difficulties to apply damping function to the wall with solid included case. Can you give me some reference about it? thanks a lot Quote:
|
||
![]() |
![]() |
![]() |
![]() |
#9 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Hello Kanarya,
I'm finishing a paper on the subject but is not yet pusblished. I can try and point in the right direction, but I cannot as of now provide you with some of the coding. I'm sure you understand. So, the papers that helped me out were the following: - C. M. Hrenya [1995] Comparison of low Reynolds number κ—ε turbulence models in predicting fully developed pipe flow - J. J. Costa [1999] Test Of Several Version For The k-e Type Turbulence Modelling - On the Mixture Model for Multiphase Flow Also, remrmber that meshing is always an issue. Hope this helps and let me know if you need anything. Best Regards, Rui |
|
![]() |
![]() |
![]() |
![]() |
#10 | |
Senior Member
Join Date: May 2011
Posts: 231
Rep Power: 17 ![]() |
Hi Rui,
Thanks for the quick answer! Did you use mixture approach or dispersed one? What is your application e.g gas-solid , gas-liquid, dense or dilute? Because I am simulating gas solid CFB system and I want to include in both equation source term which includes the momentum interchange between two phases! Thanks a lot again! Quote:
|
||
![]() |
![]() |
![]() |
![]() |
#11 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Hi,
I'm using the Mixture Model because I´m modelling a solid-liquid dense suspension. Since you are gas-solid, I recomend the works of Elghobashi (I believe it is spelled this way). Best Regards, Rui |
|
![]() |
![]() |
![]() |
![]() |
#12 | |
Senior Member
Join Date: May 2011
Posts: 231
Rep Power: 17 ![]() |
Hi Rui,
thanks for your time and patients! did you get improvement near the wall without wall treatment (dense mesh) in comparison to classical models? I am looking forward to read your paper! thanks! best! kanarya Quote:
|
||
![]() |
![]() |
![]() |
![]() |
#13 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Yes, I did.
The classic wall function behaves very poorly with particles, at least in solid-liquid case that I study. Best Regards, Rui |
|
![]() |
![]() |
![]() |
![]() |
#14 | |
Senior Member
Join Date: May 2011
Posts: 231
Rep Power: 17 ![]() |
Hi Rui,
what do you mean with "Also, remember that meshing is always an issue"? do we need dense mesh near the wall for damping function as well (like Y+ =1 or Y+ =30). Y+ = 30 should be enough,right? thanks in advance! Best! Kanarya Quote:
|
||
![]() |
![]() |
![]() |
![]() |
#15 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
Hi Kanarya,
I think that for Low Re models you should go for Y+=1. This is due to the anisotropic behaviour near the wall. The meshing issue comes from two points: 1) refine mesh until the results do not vary and 2) the RAM limitations for really dense meshes. Hope this helps. Best Regards, Rui |
|
![]() |
![]() |
![]() |
![]() |
#16 | |
Senior Member
Join Date: May 2011
Posts: 231
Rep Power: 17 ![]() |
Thanks a lot Rui!
Quote:
|
||
![]() |
![]() |
![]() |
![]() |
#17 |
Senior Member
Join Date: May 2011
Posts: 231
Rep Power: 17 ![]() |
Hi Rui,
Did you publish your paper about damping function in gas solid multiphase flows. can you give me some referance about it? thanks! |
|
![]() |
![]() |
![]() |
![]() |
#18 |
Member
Join Date: Apr 2011
Posts: 56
Rep Power: 16 ![]() |
My paper is on Solid-liquid multiphase flows.
I'mm finalizing the paper and will submit it soon. If I get accpeted for publication I'll share the link here. I appologize if I gave the wrong impression. Best Regards, Rui |
|
![]() |
![]() |
![]() |
Tags |
k epsilon, low reynolds, model functions |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
low reynolds number models in Fluent | doug | Main CFD Forum | 6 | August 4, 2012 14:39 |
low Reynolds Model for pipe flow | RugbyGandalf | OpenFOAM | 9 | July 4, 2011 11:28 |
Wall functions for near wall treatment : k - epsilon model | fivos | Main CFD Forum | 4 | April 27, 2011 07:44 |
low reynolds k omega / wall functions | stawrogin | OpenFOAM | 1 | March 30, 2011 06:04 |
SimpleFoam k and epsilon bounded | nedved | OpenFOAM Running, Solving & CFD | 1 | November 25, 2008 20:21 |