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How to obtain the residence time in the particle tracing module

Posted 13 feb 2012, 22:11 GMT-5 Charged Particle Tracing, Particle Tracing for Fluid Flow Version 5.1 4 Replies

John R Puentes
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I ran a simulation of a polymeric solution inside an extrusion die by using laminar flow and carreau model. Afterwards, I implemented the particle tracing module, beacuse I am interested in the residence time which is the time a particle takes to exit the die. I wonder how can I obtain a graphic of the average time of the particles which exit the die.

Is it similar to particle release time (fpt.prt)?

Thanks
4 Replies Last Post 19 ago 2015, 15:28 GMT-4
Daniel Smith COMSOL Employee

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Posted: 1 decade ago 14 feb 2012, 08:54 GMT-5
You need to add an auxiliary dependent variable and set the source to 1. This will solve the additional ODE per particle:

d(rp)/dt = 1

which means rp is the residence time. After solving, create a histogram of rp at the final timestep. This will give you the residence time distribution.
You need to add an auxiliary dependent variable and set the source to 1. This will solve the additional ODE per particle: d(rp)/dt = 1 which means rp is the residence time. After solving, create a histogram of rp at the final timestep. This will give you the residence time distribution.
John R Puentes
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Posted: 1 decade ago 20 feb 2012, 15:27 GMT-5
I wonder if you can explain me in which step should I add the new variable. Is it when defining the boundary conditions or when definining the time dependent steps?

Thanks in advantage.
I wonder if you can explain me in which step should I add the new variable. Is it when defining the boundary conditions or when definining the time dependent steps? Thanks in advantage.
Sepideh Ramezani
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Posted: 9 years ago 19 ago 2015, 14:14 GMT-4
Hi Dan,

And how is it possible to calculate mean and variance of residence time of the particles?

I mean how to draw these graphs in comsol?

Sepideh
Hi Dan, And how is it possible to calculate mean and variance of residence time of the particles? I mean how to draw these graphs in comsol? Sepideh
Daniel Smith COMSOL Employee

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Posted: 9 years ago 19 ago 2015, 15:28 GMT-4
Suppose you have an auxiliary dependent variable called rp for the residence time. The mean residence time would be given by:
fpt.fptaveop1(rp)

for a Particle Tracing for Fluid Flow interface with tag fpt. fptaveop1 is an average operator defined over the particles (see the Component Couplings section on P34 of the V5.1 Particle Tracing Module User's Guide for more info).

The variance would be defined as:
fpt.fptaveop1(rp^2)-fpt.fptaveop1(rp)^2

These can be plotted using a 1D Plot Group and a Global plot type.
Suppose you have an auxiliary dependent variable called rp for the residence time. The mean residence time would be given by: fpt.fptaveop1(rp) for a Particle Tracing for Fluid Flow interface with tag fpt. fptaveop1 is an average operator defined over the particles (see the Component Couplings section on P34 of the V5.1 Particle Tracing Module User's Guide for more info). The variance would be defined as: fpt.fptaveop1(rp^2)-fpt.fptaveop1(rp)^2 These can be plotted using a 1D Plot Group and a Global plot type.

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