# PBM in settling tank

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 November 11, 2014, 19:36 PBM in settling tank #1 New Member   Nicolas Join Date: Jun 2009 Posts: 19 Rep Power: 15 Hi, I am working with a secondary settling tank and I want to incorporate to the simulation a Population Balance Modelling (PBM) in order to represent the flocculation process in the system. The PBM model I want to use is called the Parker PBM and is represented by these equations: (dϕ_p)/dt=K_b ρϕ_f G^m-K_a ρϕ_f ϕ_p G (dϕ_f)/dt=-K_b ρϕ_f G^m+K_a ρϕ_f ϕ_p G The model consider two classes of solid particles, the primary particles and the flocs. To represent the solid phases I want to use the passive scalar optional model as an additional scalar partial differential equation. The equation of this model has a source term in which I pretend to incorporate the PBM as a field function. Therefore, I create two passive scalars to represent the two solid phases of the PBM model. Here I have a doubt: when I run a simulation, does the passive scalar represent a volume fraction? If it is not, when I define in which part of the region the passive scalar enter to the system, what represent the number I select. Additionally, I want to incorporate a correlation to describe the settling velocity. According to a literature review done, to incorporate this correlation I have to replace the velocity component (v_g) of the transport equation of the passive scalar model with the settling velocity. If I create a field function with the correlation where can I use it? In this moment, I am trying to incorporate this in the source term, so I will create a field function that includes the PBM model and the settling velocity equation. Has somebody worked with a PBM in star?

 Tags passive scalar, pbm, settling