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Old   June 11, 2010, 08:24
Default Rosin Rammler Distribution
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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

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Sorry, I wanted to post this to the OpenFOAM Forum. Can someone move this thread there?
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Old   June 11, 2010, 19:17
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I believe this is the mean diameter of the particles.
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Old   June 14, 2010, 05:58
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The Problem is that changing d to lower values (60Ám to 20Ám) results in a shift of the maximum to the right at a PDF-Histogramm:

time after injection 1000ms:

d=60Ám

d=20Ám


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?
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Old   June 14, 2010, 11:00
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Joseph Urich
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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.
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Old   August 23, 2010, 08:18
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X.G. Li
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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
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Old   August 23, 2010, 09:12
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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:
f(d) = \frac{n}{d_{mean} \Gamma ( 1-3/n ) } (  \frac{d}{d_{mean}} )^{n-4}  exp (- (  \frac{d}{  d_{mean}} )^n )

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

Last edited by mystix; August 23, 2010 at 09:32.
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