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December 9, 2010, 07:58 
Tomiyama wall lubrication force

#1 
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Hi Foamers,
I am developing a EulerEuler solver for twophase flow. For the moment I only consider an adiabatic case and no interfacial area concentration transport equation (IACTE). [At a later stage, I will implement boiling and IATCE but this is not my goal right now] I implemented the following interfacial forces :  Ishii Zuber drag  Zuber virtual mass  Gosman (Favre averaged) turbulent dispersion  Tomiyama lift  Tomiyama wall lubrication My case is based on the DEDALE experiment performed at EDF, which consists of a upwards water flow in a vertical pipe, in which is injected gas bubbles. No heating is applied. I even makes it simpler cause i consider basically a 2D channel instead of a 3D pipe. However, my wall lubrication force seems to be wrong cause for 0.6 mm diameter bubbles, i do not observe wall peaking (the void fraction is maximum at the wall, like if the wall lubrication force was not big enough to countereffect the lift). Then I tried to run a new simulation for 2mm diameter bubbles and my code crashed after 0.002s of simulation, the wall lubrication force had tremendously increased and made the gas velocity explode (500 m/s). I am a bit confused about this Tomiyama wall lubrication force. Concerning the relative velocity which is needed for its calculation, is it the relative velocity for each local cell, or at the centerline location? Should it be the total magnitude of the relative velocity or only the part in the flow direction? Here is what I implemented for this force : Code:
volScalarField AWallLubrication = wallLubricationa>AWL(alpha,DS,magUr); //calls a volVectorField wallLubricationForce = AWallLubrication*(1/pow(distToWall,2)1/pow(DdistToWall,2))*normal // I checked distToWall and D (the pipe diameter) and these fields are OK so the pb might be in AWL Code:
dimensionedScalar g ( "g", dimensionSet(0, 1, 2, 0, 0, 0, 0), scalar (9.81) ); volScalarField Eo = mag(g)*(phaseb_.rho()phasea_.rho())*pow(DS,2.0)/phaseb_.sig(); volScalarField CwlEo = exp(0.933*Eo+0.179); forAll(Eo, celli) { if (Eo[celli] < 1.0) { CwlEo[celli] = 0.47; } else if (Eo[celli] >= 1.0 && Eo[celli] <= 5.0) { CwlEo[celli] = exp(0.933*Eo[celli]+0.179); } else if (Eo[celli] > 5.0 && Eo[celli] <= 33.0) { CwlEo[celli] = 0.00599*Eo[celli]0.0187; } else if (Eo[celli] > 33.0) { CwlEo[celli] = 0.179; } } return 0.5*CwlEo*phaseb_.rho()*pow(Ur,2.0)*DS; //DS is the bubble diameter Has anyone already implemented Tomiyama wall lubrication force? Or see what might be wrong in my implementation? Any other idea, suggestion is welcome. Thanks in advance. Best, /Edy 

December 9, 2010, 15:37 

#2 
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Hi Edy,
nice!
Hope this helps! best regards,
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December 9, 2010, 16:11 

#3 
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Juho Peltola
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Perhaps it would be better to implement the model proposed by Frank (2004). It is a version of the Tomiyama model for general geometries i.e. not just for circular pipes. This model is implemented in CFX (along with others). You can find more information on Frank's homepage: http://www.drthfrank.de
Here's one presentation: http://www.drthfrank.de/publications...op_Dresden.pdf I definitely understand why you suggest this, but do you happen to have references for this kind of practice or examples of codes that do this? 

December 10, 2010, 01:59 

#4  
Senior Member

Quote:
Quote:
We should consider to do so in OpenFOAM @Edy: We have implemented quite a lot models for bubbly flows. Are you interested in sharing them? We could found a working group on the extend portal (www.extendproject.de) on the enhancement of bubbleFoam. I.e. adding proper turbulence models, a bench of interfacial force models, swarm correlations etc.
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Holger Marschall web: http://www.holgermarschall.info mail: holgermarschall@yahoo.de 

December 10, 2010, 02:42 

#5  
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Juho Peltola
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Quote:


December 10, 2010, 02:56 

#6 
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Hi Juho,
yes  closure modeling is a dirty business May I ask your topic of research? best regards,
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Holger Marschall web: http://www.holgermarschall.info mail: holgermarschall@yahoo.de 

December 10, 2010, 03:10 

#7 
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Juho Peltola
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December 10, 2010, 05:29 

#8 
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Hi!
I see that you've been quite active on the forum yesterday evening. Thank you both for your very useful advices. I had checked before and my wall lubrication force is in the proper direction. I also implemented the Antal wall lubrication model but have not tested it yet. I was in the beginning a bit suspicious about your argument, consisting of suspending the lift force for near wall cells, cause it seemed to me kind of "cheating". But your explanation convinced me : since the wall lubrication force has been introduced in order to fit the experimental results and not out of mechanical modeling, i dont see why one could not "play" a bit with the lift force as well. So I will try that, suspending or damping my lift force, keeping Tomiyama version in a first time. Have you already done that? If you have, did you suspend the lift only for cells in contact with the wall or for few layers of cells near the wall? In a second time, I'll try the Frank formulation, whose geometryindependence makes it quite interesting, as you mentioned. I'll let you know about the results as soon as I got some. @Holger : How exactly work this working group? (in few words, I ll have a look at the webpage). I would be very interested, that's in my opinion the main advantage of OpenFOAM, to be able to share already implemented solvers between Foamers. Unfortunately, i cannot provide my current solver (I signed a confidentiality agreement with a company I am working with) but I'd be glad to exchange ideas and eventually my future pieces of code, if I am allowed to. Best, /Edy 

December 10, 2010, 06:01 

#9  
Senior Member

Hi Edy,
Quote:
Quote:
best,
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Holger Marschall web: http://www.holgermarschall.info mail: holgermarschall@yahoo.de 

December 10, 2010, 06:20 

#10 
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Laurence R. McGlashan
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I've put my surface forces library up on github:
https://github.com/lrm29/multiphaseSurfaceForces https://github.com/lrm29/multiphaseTransport I haven't really done much, but Antal/Frank wall lubrication forces are in there. Would be good to share this stuff as it's pretty simple to implement, but easy to make mistakes!
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Laurence R. McGlashan :: Website 

December 13, 2010, 11:41 

#11 
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Hi,
Thanks Laurence for your models. Your Antal wall lubrication force will be useful to me. I have not yet implemented it because my results with Tomiyama are satisfying for the moment, and I first want to have a complete solver which is valid for pipe before eventually improve it and make it geometry independent. As I said, here is the void fraction profile I get at a location z/D=55, which is pretty satisfyong compared to the DEDALE experiment. However my IAC and bubble diameter (DS) profiles are not good but the discrepancies for these two terms cancel out and give in the end a correct void fraction. Does any of you have an idea of what might cause the discrepancy on IAC and DS. In my IACTE, I used HibikiIshii models for coalescence and breakup. You can find to the following adress my profile predictions, as well as the experimental data. http://dl.free.fr/jBPxNlvhz Thanks in advance, Best /Edy 

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