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Old   July 7, 2009, 04:59
Default help about volume fraction
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Qiaojie Li
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hi all
in CFX, volume fraction is defined as the fraction of the control volume occupied by that phase.(right?) is this ,for example,i have 57%(volume fraction)metal power and 43% binder mix together, and should i set the volume fraction of metal powder is 0.57 and the binder is 0.43? thanks!
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Old   July 7, 2009, 05:41
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yes however it depends on how you want to initialise your problem.

if the two phases are uniformly distributed in your domain then use the values you mentioned to set one of the phase and leave the other on automatic. if your problem has byoancy effects or your initialisation needs a bit more control you will need to define it using ccl.

if you have gas/liquid mixtures make sure you calcualte the state and expansion of the gas (density,ideal gas law) depending on the inlet conditions (temp,presure)
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Old   July 10, 2009, 04:46
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hi George
I want to simulate a metal injection molding process using CFX.In this situation , we mix the metal powder(solid particle) with the binder(continuous liquid) together,the metal powder have a high volume farction(50%-75%).which model should i use? solid particle collision models? How can i monitor the filling process, i mean how to determine is full filled or not? thanks!
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Old   July 10, 2009, 06:14
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1) what you want to get from your simulation; "simulate a metal injection molding process" is not a well defined description

2) what you mean "How can i monitor the filling process, i mean how to determine is full filled or not". you have logical criteria that you determine if the process is "full or not" can you write these criteria using maths?

3) you need to look into the differences between eulerian-eulerian and lagrangian-eulerian multiphase models. usually for mixing vessels if you're not interested for particle collision or you have a lot of particles engineers go for eulerian-eulerian multiphase models however it does depend what you want to do.
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