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Get phase diameter udf fluent

  1. Apr 17, 2015 #1
    Hi everyone! I'm trying to simulate the encapsulation of pancreatic islets in a very simple chamber. It is made of one cylinder with diameter of 10mm, a coaxial capillary of diameter 1mm. In the cylinder there is a oilic phase and in the capillary flow polymeric material and islets. when islet plus polymer exit from capillary,they meet oil in a convergent situated at the base of the cylinder. This convergent is connected to another capillary, where flow encapsulated islets.
    In the small capillary flow polymeric material and islet(respectively 87% and 13% of volume fraction), in the large capillary flows oil(100%). At the outlet of the small capillary, the islet should come encapsulate, thanks to the action of the instability of Rayleigh-Plateau and also to the action of the oil on the polymeric material. In other words these islets are inside a coating of polymeric material (named conformal). These two flows (oil and polymeric material plus islets) are coaxial flows.
    I am trying to write a udf that permits me to calculate the coating thickness.
    My idea is to create planes in the convergent and evaluate on them the coating thickness by a volume fraction study. In other words, on this plane my udf must calculate the volume fraction of islets and water, must remove the cells that contains a vof<0.0505, and least must evaluate the diameter of these two phases.
    I think it's possible to do, but i have several problems.
    First of all, I don't know if it's possible declare two or more phases when I use, for example, C_VOF(c,t). "t" is my thread: is it possible to declare two phase, using for example pt[1,2]?
    Another problem is the function C_PHASE_DIAMETER(c,t). In various forums I found it use in this way "C_PHASE_DIAMETER(f,t). But, why put "f" and no "c"?

    My udf is this:

    /*C_PHASE_DIAMETER*/

    #include "udf.h"
    #include "stdio.h"
    #include "stdlib.h"

    DEFINE_EXECUTE_AT_END(diameter)
    {
    Domain *d=Get_Domain(1);
    Thread **pt;
    Thread *t;
    cell_t c;
    float diam_islet;
    float diam_water_islet;
    float radius_islet;
    float radius_water;
    float coating;
    float vof_islet;
    int ID[3]={3,10,13};
    int i;
    diam_islet=0.;
    radius_islet=0.;

    i=0;

    mp_thread_loop_c(t,d,pt)
    {
    begin_c_loop(c,t)
    {

    for(i=0;i<=2;i++)
    {
    t=Lookup_Thread(d,ID);
    vof_islet = C_VOF(c,pt[2]);
    vof_water = C_VOF(c,pt[1]);
    printf("%f\n", vof_islet);

    if (vof_islet>0.0505 && vof_islet<=1)
    {

    diam_islet=C_PHASE_DIAMETER(c,pt[2]);
    printf ("islets diameter: %f\n",diam_islet);
    }
    }
    if (0.0505<=vof_water<=1)
    {

    diam_water=C_PHASE_DIAMETER(c,pt[1]);
    printf("water diameter: %f\n", diam_water);
    }

    radius_islet=diam_islet/2;
    printf("radius_islet: %f\n", radius_islet);

    radius_water=diam_water/2;
    printf("radius_water: %f\n", radius_water);

    coating=radius_water-radius_islet;
    printf("coating thickness is: %f\n", coating);

    }
    end_c_loop(c,t)
    }
    }}

    I have an alternative idea: I can create a udf that gives back coordinates of cells in this way: I want to get x max and x min, y max and y min and z max and z min of the islets and of the coating based on the volume fraction (based on passage between different phases). In other words, I want to obtain coordinates max and min about the interface of my phases. Is it possible?
    Another question is the following: I'm using an Euler Euler model, but the volume fraction of the islets is approximatively 13%. Is this method suitable for my problem, or DPM is more appropriate?
    Thanks a lot!
    Michela
     
  2. jcsd
  3. Apr 22, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
     
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