[mystix]

Hallo guys,

you can define a RosinRammlerPDF at the sprayProperties of the tutorial aachenbomb (dieselFoam solver).

Does anyone knows what the parameter d defines?

I think it could be the representative diameter D0.5 = drop diameter such that 50% of total liquid volume is in drops of smaller diameter. So it would be the mass median diameter (MMD).

But I dont know for sure.. can someone help me please?

Best regards
mystix

-----------
Sorry, I wanted to post this to the OpenFOAM Forum. Can someone move this thread there?

[Nam]

I believe this is the mean diameter of the particles.

[mystix]

The Problem is that changing d to lower values (60µm to 20µm) results in a shift of the maximum to the right at a PDF-Histogramm:

time after injection 1000ms:

d=60µm

d=20µm


I would like to know how the RosinRammler Distribution works in OF. Do I define the distribution of parcels at the starting and how can I controll it?

[jurich]

Hello,

There are source files for a Rosin Rammler pdf in the directory src/thermophysicalModels/pdfs/RosinRammler. I didn't trace the dependencies to be certain if this is called by dieselFoam, but it seems likely. It might offer you more information.

[CYMa]

The Rosin-Rammler distribution is frequently used to describe the particle size distribution of powers of various types and sizes. The function is particularyly suited to representing particles generated by grinding, milling and crushing operations. The conventional Rosin-Rammler function is described by (1)

where R is the retained weight fraction of particles with a diameter greater than D, D is the particle size and is the mean particle size, and n is a measure of the spread of particle sizes. The Cumulative Distribution Function (CDF) is therefore (2)

As an additional note, the PDF is: Parameters:

Dmmean particle diameternmeasure of the spread of particle sizesDparticle size

[mystix]

Thank you for answer, CYMa.

I agree, that the cumulative distribution rosin rammler function is right.

But I found in

J. Madsen
Computational and Experimental Study of Sprays from the Breakup of Water Sheets.
Dissertation, Faculty of Engineering and Science, Aalborg University, 2006.

Page 207,

that the probability density function is:


What is correct?
Where did you get your eq from?

[saeedshayae]

Hello CFDmans

This is exactly my question. what is Rosin Rammler parameter d in SprayCloudProperties in sprayFoam solver? Does anyone knows what the parameter d defines and how we can set value for it?

            sizeDistribution
            {
                type        RosinRammler;

                RosinRammlerDistribution
                {
                    minValue        1e-06;
                    maxValue        0.000120;
                    d               0.000020;//what is this????
                    n               3;
                }
            }

Best regards
Saeed

[dinh]

min and max values is to ensure the range of the particle size within the min and max.
d and n can be referred to Fluent manual
http://www.afs.enea.it/project/neptu...ug/node692.htm

Originally Posted by saeedshayae

Hello CFDmans

This is exactly my question. what is Rosin Rammler parameter d in SprayCloudProperties in sprayFoam solver? Does anyone knows what the parameter d defines and how we can set value for it?

            sizeDistribution
            {
                type        RosinRammler;

                RosinRammlerDistribution
                {
                    minValue        1e-06;
                    maxValue        0.000120;
                    d               0.000020;//what is this????
                    n               3;
                }
            }

Best regards
Saeed

[saeedshayae]

Originally Posted by dinh

min and max values is to ensure the range of the particle size within the min and max.
d and n can be referred to Fluent manual
http://www.afs.enea.it/project/neptu...ug/node692.htm

thank you Mr Dinh

Based on this link you referred (Fluent manual), for obtaining d (or dbar) and n we must have particle size data (Mentioned table in this link ), but we want to simulate spray and we don't have any experimental data about particle size before simulation!!!

Is there any source or reference for setting d to set value without help of experimental data (like n as i mentioned last post)??

[jairoandres]

Then you need to find a paper where they relate the atomizer physical and operational characteristics to the size distribution. I have seen some for rotary atomizer and surely there should be others for air blast and other different types.

[HPE]

`d` is the `scale parameter` (aka lambda) and `n` is the `shape parameter` in the Rosin-Rammler (aka Weibull) probability density function; `d` is not the mean or any other moment of the distribution. Note that in OpenFOAM's implementation the Rosin-Rammler distribution is the doubly-truncated two-parameter variant (yes, there are one-parameter, and three-parameter variants as well).

Hope this helps.