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Dense discrete phase model

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Old   August 10, 2012, 02:57
Default Dense discrete phase model
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Theerawat
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Hi, I want to know how can I use dense discrete phase model in Eurlerian model
what is the transition factor, If I wanna specify volume fraction, what should I do?

Thank you very much
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Old   August 10, 2012, 09:45
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Hi,

Using a scalar transport equation (UDS) is a good alternative in Eulerian modelling but it makes sense if the particle diameters are in nano range.

Bests,
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Old   April 28, 2014, 06:01
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Hello everyone,

I would like to re-asked the questions of Theerawat, because I think his questions are relevant. After reading the ansys doc, my ideas aren't clear at all.

What is the difference between Dense DPM and DPM?

Then, what is the transition factor used for?

Ansys Doc:
"Enable Volume Fraction Approaching Continuous Flow Limit to specify a Transition Factor. The Transition Factor is multiplied by the theoretical close-packing limit for mono-sized spheres (PI/(3*\sqrt{2} = 3/4) to determine the transition volume fraction. The default value for the Transition Factor is 0.75, giving a transition volume fraction of 0.5625 (PI/(3*\sqrt{2} = 3/4)."

What is "the theoretical close-packing limit for mono-sized spheres" and what is transition volume fraction?

I know it's a lot of questions but it will be very useful if someone could bring his knowledge.

Thanks you very much,
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Old   December 5, 2014, 04:32
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Hello!

Does anybody know where it is possible to find any tutorial on DPM, DEM and/or Dense DPM models?

Thank you!
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Old   April 15, 2015, 12:44
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Victor Liblin
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Quote:
Originally Posted by LoUcAsss View Post
Hello everyone,

I would like to re-asked the questions of Theerawat, because I think his questions are relevant. After reading the ansys doc, my ideas aren't clear at all.

What is the difference between Dense DPM and DPM?

Then, what is the transition factor used for?

Ansys Doc:
"Enable Volume Fraction Approaching Continuous Flow Limit to specify a Transition Factor. The Transition Factor is multiplied by the theoretical close-packing limit for mono-sized spheres (PI/(3*\sqrt{2} = 3/4) to determine the transition volume fraction. The default value for the Transition Factor is 0.75, giving a transition volume fraction of 0.5625 (PI/(3*\sqrt{2} = 3/4)."

What is "the theoretical close-packing limit for mono-sized spheres" and what is transition volume fraction?

I know it's a lot of questions but it will be very useful if someone could bring his knowledge.

Thanks you very much,
"The theoretical close-packing limit for mono-sized spheres" is simply the maximum volume that spheres can actually take within a cubic volume. For instance, the face-centered cubic system is known as the most dense sytem of them all :
PI/(3*sqrt(2)) is obtained by trying to dertermine this value.

To understand the factors, considers this example :
if you fill a pipe with mono-sized particles up to its half, then finish to fill it up with water, the transition factor is 0.5 BUT in fact you had to put in more than 0.5*V of water right ?
The transition volume fraction (which is the actual fraction of the volume taken by the spheres) is then 0.5*PI/(3*sqrt(2)).

Hope this answers you question.

Best regards,
Victor
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Old   April 19, 2016, 17:30
Smile Transition factor
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Leo
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Hello everybody,

I am a kind of new on this forum and I have recently start working on the lagrangian (DDPM) implementation of my bench reactor (solid-gas sold system). I have been working with the TFM so far and when I switched to the Lagrangian model I have at first considered the DEM to account for particle particle interaction but now I have found more convenient to apply the KTGF approach to account for particle collision since most of the properties to be define for the granular phase are already known from my previous simulation with the TFM. Neverthless I have still some doubts about the proper implementation of such a model and one of the main one is the "transition factor" (and relating concept of "volume approaching the continuos phase"). In my case I have a cylindrical bed 20 inches high which is (at rest) fulfilled with allumina powder at the 50 % (10 inches). Now I still don't understand how to use this factor because I don't understand how this parameter relates to the physic of the problem. Is there someone who found proper material or who has understood what this parameter means exactly and how to extimate its value according to the specific case. I saw the example relating to the particles and the water but I did not understand it honestly,
Thank you very much for your attention and support,

Leonardo
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Old   April 21, 2016, 16:13
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Quote:
Originally Posted by victor.liblin View Post
"The theoretical close-packing limit for mono-sized spheres" is simply the maximum volume that spheres can actually take within a cubic volume. For instance, the face-centered cubic system is known as the most dense sytem of them all :
PI/(3*sqrt(2)) is obtained by trying to dertermine this value.

To understand the factors, considers this example :
if you fill a pipe with mono-sized particles up to its half, then finish to fill it up with water, the transition factor is 0.5 BUT in fact you had to put in more than 0.5*V of water right ?
The transition volume fraction (which is the actual fraction of the volume taken by the spheres) is then 0.5*PI/(3*sqrt(2)).

Hope this answers you question.

Best regards,
Victor

Hello everybody,

I am a kind of new on this forum and I have recently start working on the lagrangian (DDPM) implementation of my bench reactor (solid-gas sold system). I have been working with the TFM so far and when I switched to the Lagrangian model I have at first considered the DEM to account for particle particle interaction but now I have found more convenient to apply the KTGF approach to account for particle collision since most of the properties to be define for the granular phase are already known from my previous simulation with the TFM. Neverthless I have still some doubts about the proper implementation of such a model and one of the main one is the "transition factor" (and relating concept of "volume approaching the continuos phase"). In my case I have a cylindrical bed 20 inches high which is (at rest) fulfilled with allumina powder at the 50 % (10 inches). Now I still don't understand how to use this factor because I don't understand how this parameter relates to the physic of the problem. Is there someone who found proper material or who has understood what this parameter means exactly and how to extimate its value according to the specific case. I saw the example relating to the particles and the water but I did not understand it honestly,
Thank you very much for your attention and support,

Leonardo
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