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Old   February 17, 2016, 03:22
Default Particle residence time
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Unnikrishnan T P
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I'm doing a spray simulation. How can I calculate the residence time of particles? Is there any way within Converge itself?
I post process using EnSight. But I dint find a way there. Please reply if anyone has a solution...
Thank you
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Old   February 19, 2016, 17:00
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Quote:
Originally Posted by unnikrishnan View Post
I'm doing a spray simulation. How can I calculate the residence time of particles? Is there any way within Converge itself?
I post process using EnSight. But I dint find a way there. Please reply if anyone has a solution...
Thank you
Hello There,

In CONVERGE we have a parcel variable called lifetime. I think this is what you wanted. You can quote this variable via a UDF. However, we don't output this variable directly to our post files. In our UDF user_post.c you should see lines like below
parcel->user[0] = 0.0;
parcel->user[1] = pow((parcel->radius),3)*(4.0/3.0)*PI*(parcel->density)*(parcel->num_drop);
parcel->user[2] = parcel->radius;

You can change the first line to
parcel->user[0] = parcel->lifetime;

Then go to udf.in and set
3 user_num_parcel
Next go to post.in and add
user[0] under <parcel>

Last, run CONVERGE with the user_post UDF.

You will be able to visualize the parcel lifetime (variable user_0) from Ensight

Please let us know if this will work for you.

Thanks,

Yunliang
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Old   February 20, 2016, 03:25
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Unnikrishnan T P
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Thank you so much. Certainly I'll try this and let you know.
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Old   September 16, 2016, 03:34
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Quote:
Originally Posted by ywang89 View Post
Hello There,

In CONVERGE we have a parcel variable called lifetime. I think this is what you wanted. You can quote this variable via a UDF. However, we don't output this variable directly to our post files. In our UDF user_post.c you should see lines like below
parcel->user[0] = 0.0;
parcel->user[1] = pow((parcel->radius),3)*(4.0/3.0)*PI*(parcel->density)*(parcel->num_drop);
parcel->user[2] = parcel->radius;

You can change the first line to
parcel->user[0] = parcel->lifetime;

Then go to udf.in and set
3 user_num_parcel
Next go to post.in and add
user[0] under <parcel>

Last, run CONVERGE with the user_post UDF.

You will be able to visualize the parcel lifetime (variable user_0) from Ensight

Please let us know if this will work for you.

Thanks,

Yunliang
Sir, am also looking DPM, liquid + 5microns of solid particles, here am not getting how to calculate the particle residence time. Please let me know am troubling too muchh.
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Old   September 16, 2016, 03:42
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WIth a given particular time, particle cant able to travel entaire length of the fluid domain.
My ultimate aim is to compare the particle residence time with difference reynolds number.

How i can go with this problem, please let me know..
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Old   September 16, 2016, 18:00
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Quote:
Originally Posted by pachi View Post
WIth a given particular time, particle cant able to travel entaire length of the fluid domain.
My ultimate aim is to compare the particle residence time with difference reynolds number.

How i can go with this problem, please let me know..
Parcel residence time ( it is called the lifetime in the code) is the time from the nozzle. If you can use Ensight to visualize the lifetime using the way I talked about above, you should be able to see the impact of Reynolds numbers on it.

Thanks,

Yunliang
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Old   September 17, 2016, 04:14
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Hiii ,

am looking particle residence time in the flow field.

Along with the water and am injecting some 5 microns diameter of particles with a velocity of 0.042m/s, here i have not mentioned the total mass flow rate in the injection frame.

Is this mainly affect to the flow field and am getting confuse with how to calculate total mass flow rate.

Currently, injection time am calculating based on the particle velocity(0.0425m/s) and my domain length(5m) soo travel to this length it needs approximately 117s. IS this correct.
Please let me know am worried too much.
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Old   September 19, 2016, 11:14
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Quote:
Originally Posted by pachi View Post
Hiii ,

am looking particle residence time in the flow field.

Along with the water and am injecting some 5 microns diameter of particles with a velocity of 0.042m/s, here i have not mentioned the total mass flow rate in the injection frame.

Is this mainly affect to the flow field and am getting confuse with how to calculate total mass flow rate.

Currently, injection time am calculating based on the particle velocity(0.0425m/s) and my domain length(5m) soo travel to this length it needs approximately 117s. IS this correct.
Please let me know am worried too much.
Hello,

From the file mass_avg_flow.out, you can see the flow rates of both the liquid and parcel. If the mass flow rate of parcels is significant compared with that of the liquid flow, it will affect the liquid flow. Small parcels will follow the fluid to flow. Therefore the parcels may reach a higher velocity later. This mean the residence time should be shorter than 117 s if the water velocity is higher than 0.042 m/s.
Thanks,
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Old   September 19, 2016, 14:42
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Originally Posted by ywang89 View Post
Hello,

From the file mass_avg_flow.out, you can see the flow rates of both the liquid and parcel. If the mass flow rate of parcels is significant compared with that of the liquid flow, it will affect the liquid flow. Small parcels will follow the fluid to flow. Therefore the parcels may reach a higher velocity later. This mean the residence time should be shorter than 117 s if the water velocity is higher than 0.042 m/s.
Thanks,
Thank you very much Ywang.

Yeah,

i tried its working nicely. Thank you soo much.
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Old   September 19, 2016, 14:50
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Hii Y wang,

One more doubt,

Now my simulation running with unsteady liquid with steady flow particle feeding in the domain.

In the post processing some particles were incomplete/stopped in between.
it means ????

And how to know number particles traveling in the flow. Mine feeding is steady with flow rate of 0.092 kg/s.

Thank you...
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Old   September 19, 2016, 15:33
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Quote:
Originally Posted by pachi View Post
Hii Y wang,

One more doubt,

Now my simulation running with unsteady liquid with steady flow particle feeding in the domain.

In the post processing some particles were incomplete/stopped in between.
it means ????

And how to know number particles traveling in the flow. Mine feeding is steady with flow rate of 0.092 kg/s.

Thank you...
Hello,

After some time, both the liquid flow and particulate phase will reach the steady state. From spray.out you can see the number of parcels in the domain. If the number of parcels in the domain is not changing, you can say it has reached the steady state. I don't understand your first question "some particles were incomplete/stopped."
Thanks,
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Old   September 21, 2016, 03:01
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Quote:
Originally Posted by ywang89 View Post
Hello,

After some time, both the liquid flow and particulate phase will reach the steady state. From spray.out you can see the number of parcels in the domain. If the number of parcels in the domain is not changing, you can say it has reached the steady state. I don't understand your first question "some particles were incomplete/stopped."
Thanks,
Thank you Ywang,

Some of the particles, while traveling in the flow they stopped in between in the domain. Their path lines are incomplete. it means??
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Old   September 21, 2016, 16:44
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Can you check the parcel velocity to see if it is very low?
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Old   September 22, 2016, 01:14
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Can you check the parcel velocity to see if it is very low?
During transient case, liquid reynolds number varies from 200 to 1000, hence at inlet for particles i defined avg Reynolds number(600).

Tube had constrictions(80% area reduction), because of recirculation zones in the downstream might be velocity of fluid/particles will become neutral ie fine.

However, when i look in the upstream some of the particles stopped before crossing the constrictions.
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