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Low Reynolds K Epsilon Launder Sharma Model Functions Doubt... |
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January 10, 2012, 11:58 |
Low Reynolds K Epsilon Launder Sharma Model Functions Doubt...
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#1 |
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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 |
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January 10, 2012, 13:30 |
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#2 |
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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.
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January 10, 2012, 17:38 |
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#3 |
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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 |
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January 11, 2012, 10:23 |
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#4 |
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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 |
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January 12, 2012, 11:45 |
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#5 |
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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 |
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August 1, 2013, 07:55 |
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#6 |
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hi Rui,
Did you manage to apple the model in two phase model? Quote:
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August 5, 2013, 10:05 |
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#7 |
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Hello Kanarya,
yes I was. I am using it now in my simulations. How can I help you? Best Regards, Rui |
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August 5, 2013, 10:40 |
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#8 | |
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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:
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August 5, 2013, 11:24 |
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#9 |
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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 |
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August 5, 2013, 11:48 |
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#10 | |
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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:
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August 5, 2013, 11:52 |
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#11 |
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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 |
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August 5, 2013, 12:00 |
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#12 | |
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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:
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August 5, 2013, 12:10 |
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#13 |
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Yes, I did.
The classic wall function behaves very poorly with particles, at least in solid-liquid case that I study. Best Regards, Rui |
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September 9, 2013, 05:26 |
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#14 | |
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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:
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September 9, 2013, 07:00 |
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#15 |
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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 |
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September 9, 2013, 07:17 |
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#16 | |
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Thanks a lot Rui!
Quote:
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February 17, 2014, 05:59 |
damping function in gas solid multiphase flows
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#17 |
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Hi Rui,
Did you publish your paper about damping function in gas solid multiphase flows. can you give me some referance about it? thanks! |
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February 17, 2014, 09:52 |
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#18 |
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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 |
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k epsilon, low reynolds, model functions |
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