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Old   August 2, 1999, 07:08
Default CFX-particle flow
  #1
Eve Chapper
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Hi,

I'm using CFX and in the command file I would like to add 3-micrometer particles (of yeast) into a flow stream of water. I've tried following the example in the book but I'm extremely lost. Can anyone out there please help.

Thanks Eve
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Old   August 2, 1999, 08:53
Default Re: CFX-particle flow
  #2
Patrick Godon
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Hi there,

I am not working with CFX and I have no clue what is in that software.

However, I can try to help with particles in the flow. This is called a two-phase flow. You need to solve for the particle some additional equations where the force that act on a particle is a function of the velocity difference between the flow and the particle. THe equations might have also a different form depending on the density of the particles (if their density is close to the density of the flow then the euqations are not simplified).

In the simplest case (the Epstein regime) the particles are just dragged in the flow. There is a drag parameter in the problem with two limiting cases. If the drag is very small then the particles move almost on their own. If the drag is very large, then the particles move with the flow like tracers.

I hope this helps,

and I hope there is somebody there or here to help you with the CFX part of it.

Patrick
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Old   August 3, 1999, 05:29
Default Re: CFX-particle flow
  #3
yi
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Hi, the following is the relevant part of a command file for particle tracking. You can change it accordingly and add it into your command file.

Hope that it will help.

Yi ----------------------------------------------------------
>>CFX4 #CALC

NP=100; /* number of particles */ #ENDCALC
>>OPTIONS

PARTICLE TRANSPORT
>>MODEL DATA
>>PARTICLE TRANSPORT MODEL

>>MODEL CHARACTERISTICS

NUMBER OF PARTICLES 100

NUMBER OF ITERATIONS 1

CROSS SECTION FACTOR 1.0000E+00

SURFACE AREA FACTOR 1.0000E+00

DROPS

>>INTEGRATION PARAMETERS

TIME LIMIT 5.0000E+00

COEFFICIENT OF RESTITUTION 0.0000E+00

>>PARTICLE PROPERTIES

BASE PARTICLE DENSITY 1.0000E+03
>>MODEL BOUNDARY CONDITIONS
>>PARTICLE TRANSPORT BOUNDARY CONDITIONS

POSITIONS IN X DIRECTION #NP*1.0e-4

POSITIONS IN Y DIRECTION #NP*0.130

POSITIONS IN Z DIRECTION #NP*3.0

INITIAL PARTICLE DIAMETERS #NP*3.0e-6

PARTICLE MASS FLOW RATES #NP*1.0E-6

U VELOCITY #NP*6.0

V VELOCITY #NP*0.0

W VELOCITY #NP*0.0
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