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How to define Boundary conditions for Quadrature Method of Moment |
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#1 |
New Member
Join Date: Aug 2018
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Hi guys,
I’m working on population balance model and have some issues with the definition of QMOM boundary conditions. I used to work with descretization method and there BC was quite simple to define. It was either a log normal or a manual distribution but here with method of moment it is confusing. I can't understand how to set up a boundary value for each moment. I'm using fluent 18.2 with the mixture multiphase method. The only phenomena occur here is growth rate (2.8e-8 m/s) and the particle min and max size are 1e-7m 1e-5m respectively. Any comment would be highly appreciated. Amir |
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#2 |
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Dhiraj Lote
Join Date: Jul 2015
Location: Mumbai, India
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Hi Amir,
did you got the solution, that what are the boundary conditions for QMOM? If yes, please let me know. I am also having the same problem. Thank you |
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#3 | |
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Dhiraj Lote
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Quote:
1. At the inlet you have to decide (e.g. 1 mm, 2mm, etc) what diameter dispersed phase is entering/existing into the system. This is very simple, if you know the experimental PSD/BSD/DSD, take the mean value of the curve. 2.Suppose you decide 2mm as a inlet diameter then 0th moment (i.e. total number of bubbles) will be 1/volume of 2mm diameter i.e.238732414 (1/4.18E-9). 3. The 1st moment will be the total length. it is calculated as diameter/total volume (0.002/4.18E-9=477464). 4. The second moment will be the total area which is calculated as 0.002^2/4.18E-9 = 954.92. 5. Similarly third and fourth moments will be 0.002^3/4.18E-9= 1.9098 and 0.002^4/4.18E-9 = 0.0038. Hope this will help you. |
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#4 | |
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Quote:
It helped a lot thanks! Just to add a small point to your comment, I think for each moment and for total number definition it is necessary to consider the dispersed phase volume fraction. For instance, for 0th moment it will be the VF/total volume instead of 1/total volume and so on for higher moments. |
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#5 |
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It is been a while but if you are still on this issue here is a way that may help to define the initial moments. Total number of particles can be calculated as: N0=VF/(Kv ∙ L0^3 ) N0=total number of particles (#/m3 of solution) VF = Volumic fraction Kv = Shape factor Then the initial moments obtain as: m0 = L0^0 ∙ N0 = N0 m1 = L0^1 ∙ N0 = m0 ∙ N0 m2 = L0^2 ∙ N0 = m1 ∙ N0 m3 = L0^3 ∙ N0 = m2 ∙ N0 . . . mk = L0^k ∙ N0 |
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fluent, method of moment, population balance model |
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