# Bug in UEqn of twoPhaseEulerFoam?

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March 24, 2011, 14:21
Bug in UEqn of twoPhaseEulerFoam?
#1
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Charlie
Join Date: Dec 2010
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Hi All:

I've spent some time interpreting the UEqn.C of twoPhaseEulerFoam. The momentum equation seems OK. however, the drag term seems problematic:

See the following link for the standard momentum equation.
http://openfoamwiki.net/index.php/BubbleFoam

In the UEqn.H, the momentum equation is :

Quote:
 00022 UaEqn = 00023 ( 00024 (scalar(1) + Cvm*rhob*beta/rhoa)* 00025 ( 00026 fvm::ddt(Ua) 00027 + fvm::div(phia, Ua, "div(phia,Ua)") 00028 - fvm::Sp(fvc::div(phia), Ua) 00029 ) 00030 00031 - fvm::laplacian(nuEffa, Ua) 00032 + fvc::div(Rca) 00033 00034 + fvm::div(phiRa, Ua, "div(phia,Ua)") 00035 - fvm::Sp(fvc::div(phiRa), Ua) 00036 + (fvc::grad(alpha)/(fvc::average(alpha) + scalar(0.001)) & Rca) 00037 == 00038 // g // Buoyancy term transfered to p-equation 00039 - fvm::Sp(beta/rhoa*K, Ua) //Drag term 00040 //+ beta/rhoa*K*Ub // Explicit drag transfered to p-equation 00041 - beta/rhoa*(liftCoeff - Cvm*rhob*DDtUb) 00042 ); 00043 00044 UaEqn.relax(); 00045 }
The drag term should involve the difference between Ua and Ub, not just Ua.

I've tried to implement that (Ub-Ua), I just added the following line in the rhs:

+ fvm::Sp(beta/rhoa*K, Ub)
For the UbEqns, I've done a similar modification
Am I right? Anyone can help?

 March 24, 2011, 14:31 #2 Senior Member   Laurence R. McGlashan Join Date: Mar 2009 Posts: 370 Rep Power: 15 The explicit part of the drag that contains Ub has been transferred to pEqn.H. Have a look there and see if it makes sense to you. __________________ Laurence R. McGlashan :: Website

 March 24, 2011, 15:18 Thank you! #3 Member   Charlie Join Date: Dec 2010 Location: 415 Kinross Dr. Newark, DE 19711 Posts: 80 Rep Power: 7 Yes, Thanks for your reply, it really helps! The effect of particle-particle interaction is also included if we set g0>0, However, note that there is g0 in radial Model (we get g0 and g0Prime), and we also define g0 in ppProperties. Both alphaEqn.H and pEqn.H are using phi_pp, which involves g0, So which g0 are they using? Thank you in advance. Zhen

 March 25, 2011, 02:19 #4 Senior Member   Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,907 Rep Power: 27 If you use the kinetic theory model, you should set g0 in ppProperties to zero. __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using.

 May 25, 2011, 21:21 #5 New Member   NieYongguang Join Date: Sep 2010 Posts: 27 Rep Power: 8 Hi Alberto I am reading the code of kineticTheory in twoPhaseEulerFoam. I find there are some annotation in kineticTheory.C such as "construct the granular temperature equation (Eq. 3.20, p. 44)" in line 61. So, can you tell me which book include these equation. Furthermore, where can I find the theory about g0 in ppProperties!

May 25, 2011, 23:11
#6
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Alberto Passalacqua
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Quote:
 Originally Posted by nygbook Hi Alberto I am reading the code of kineticTheory in twoPhaseEulerFoam. I find there are some annotation in kineticTheory.C such as "construct the granular temperature equation (Eq. 3.20, p. 44)" in line 61.
Berend van Wachem 's Ph.D. thesis.

Quote:
 So, can you tell me which book include these equation. Furthermore, where can I find the theory about g0 in ppProperties!
In the literature ppMagf is identified as G(alpha) = d(pa)/d(alpha), being pa the particle pressure, and it is called "normal stress modulus". You find it in Gidaspow's early papers for example.

Best,
__________________
Alberto Passalacqua

GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats.
OpenQBMM - An open-source implementation of quadrature-based moment methods.

To obtain more accurate answers, please specify the version of OpenFOAM you are using.

 August 26, 2011, 06:11 #7 Member   Greg Melling Join Date: Nov 2010 Posts: 41 Rep Power: 7 Does anyone know how to get the van Wachem Thesis? There's nothing online. Does anyone have a pdf?

August 26, 2011, 06:41
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Florian Krause
Join Date: Mar 2009
Location: Munich
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Quote:
 Originally Posted by grjmell Does anyone know how to get the van Wachem Thesis? There's nothing online. Does anyone have a pdf?
Not true! I needed 30sec using google twice (because I knew that he got his PhD at TU Delft) to find it

http://repository.tudelft.nl/view/ir...-83b1416709a6/

enjoy!
Florian

 August 26, 2011, 06:45 #9 Member   Greg Melling Join Date: Nov 2010 Posts: 41 Rep Power: 7 Oh dear! I was googling for ages but couldnt find it...! Thanks for proving me wrong!

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