[lakhi]

Hi all

I am trying to simulate dust particles of various diameters, say, between 0.1 to 10 micro-meters, using DPM injection. Is it possible to know how many particles of different diameters escaped through the oulet in FLUENT?

Looking forward for your kind reply.

[Zaktatir]

yes cou can!

You can see how many total streams for each particle size and the associated flow rates in those streams by selecting report/discrete phase/sample and selecting your injection and a surface along which you want to monitor the particle flow.

To compare the sample data to the R-R exponential function, you determine the mass fraction for each size using the number of particle streams and the associated mass flow rate for each stream.

[lakhi]

Dear Zaktatir,

Thank you very much for your kind reply.


As you suggested by you that

"You can see how many total streams for each particle size and the associated flow rates in those streams by selecting report/discrete phase/sample and selecting your injection and a surface along which you want to monitor the particle flow"

I can only see the window as shown in attachment 1. By using this, I get a file in .dpm file format, so do I have to look into that file?







As suggested in the second paragraph

"To compare the sample data to the R-R exponential function, you determine the mass fraction for each size using the number of particle streams and the associated mass flow rate for each stream"

How do we find the mass fraction from fluent?

Sorry if the questions are too basic.

Actually I have to plot grade efficiency curve.


Is my way for simulation of dust particle wrong? I am attaching other details (fig. 2 and 3).

[Zaktatir]

you have to look in the file and more important read the manual.

[lakhi]

Dear Zaktatir

Thank you for your reply. I got it, and I will refer the manual too. Just one last question I have in my mind: To find grade efficiency, one of my friend suggested me to simulate for different dust particle size. It means that instead of defining a range of diameters at a time, he suggested me to carry out simulation for one diameter at one time. So for ten different diameters, I have to carry out simulations 10 times and find the collection efficiency in each diameter class. So using that information if we plot the graph between particle diameter Vs. efficiency, I will get grade efficiency curve. But this method will consume lot of time!

Defining efficiency, what he suggested, should be based on particle counts rather than mass of the particles collected.

Is this method correct? Actually I am interested in finding grade efficiency curve and cut-off diameter.


Your comments on above will be of great help to me. Any references on this topic will be a warm welcome.

[Zaktatir]

That is a good approach but somewaht time consuming.

You can make a sensitivity analysis and compare between the two ways.

Generally that does also depend on your particle range say if you know a priori the size distribution or you know the mean diameter or you assume a constant size for every injection or you define a lot of injections with different diameter but there you have to scale the total mass flow rate needed.

[lakhi]

Thanx Zaktatir,

As you suggested to scale down the total mass flow rate, how do we scale it?

I thought of multiple injection, say, 10 injections of different sizes and simulate it, as it will save my time a lot! But how can I get the data in terms of number of particles collected for different diameter class? Ok, I will give it a try first with ten injections.

Well, my simulations with range of diameters defined at a time with logarithmic distribution has results written in a file, which I am attaching here, but how can we use it? Is it specified in fluent manual?

Thanx for your suggestions.

[Zaktatir]

yes it is specified under :

// User's Guide :: 2 // 24. Modeling Discrete Phase // 24.7. Postprocessing for the Discrete Phase // 24.7.8. Histogram Reporting of Samples

For the question of the scaling that is the work you have to do if you choose this approach and have as sum the real total mass flow rate that is why R-R is almost used!

I do not download anything posted there I am Sorry. By the way why do you not contact your support?

[lakhi]

Thanx Zaktatir. Your suggestions were of great help to me. Hope now I will get the results soon.