defining-particle size distribution-in cfx

harry39 · April 30, 2012, 10:58

hello all,

i am doing two phase flow simulations in ansys cfx.while initialization of boundary conditions at inlet in particle behaviour tab..i have to mention the particle size distribution with a user specified discrete diametr distribution function.i have functions for both mass fraction and number fraction as a function of diameter.
how can i insert the diameter list...? and mass fraction list & number fraction list.....as a function of diameter..?

advance thanks
krish

ghorrocks · April 30, 2012, 20:52

This is covered in the tutorials on particle flows.

And please do not PM me when you have already posted the identical question on the forum.

harry39 · May 1, 2012, 03:14

Quote:

Originally Posted by ghorrocks

This is covered in the tutorials on particle flows.

And please do not PM me when you have already posted the identical question on the forum.

thank you for your reply...and i dont send private msg to you sorrry for that.
can you please tell me where can i get those tutorials on particle flows...?

thanks again
krish

ghorrocks · May 1, 2012, 20:00

The tutorials are in the help files, and the example files are in <CFX_ROOT>/examples

harry39 · May 4, 2012, 06:26

Quote:

Originally Posted by ghorrocks

The tutorials are in the help files, and the example files are in <CFX_ROOT>/examples

thanks glenn for your reply,

I am getting an error while running in cfx solver.. like " wall is placing at outlet boundary " ....error is occuring some times up to 10 iterations and more..i have tried expert parameter control..artificial buid also..but no use..still getting...problem..
can any body suggest me, what it means & how can i rectify it ? (or) Does it mean that any problem while defining the physics in ccl file... (or) in geometry ?

thanks
krish

ghorrocks · May 4, 2012, 07:47

It is not an error, it is a warning. It simply means you are getting backflow at your outlet. If it does not go away you should move your outlet downstream.

harry39 · May 4, 2012, 09:37

Quote:

Originally Posted by ghorrocks

It is not an error, it is a warning. It simply means you are getting backflow at your outlet. If it does not go away you should move your outlet downstream.

thanks again glenn for you reply,

" U mean that i have to extend my outlet geometry to rectify the problem...? or Can i neglect the warning and proceed my my simulations...?"

and one more thing is.. i have mentioned in the previous posts about defining discrete droplet size distribution..i think you havent understand my problem properly...
the point is i have data file of diameter list say for example: 10,20,30,..100 microns
i want to upload this list file to the diameter list and then i have an expression for both number fraction and mass fractions as a function of diameter,
for example: mf(mass fraction) (or) NF(number fraction)=Constant value(units are length)/Diameter
so after uploading the diameter list and these expressions it should calculate mf and Nf values for each diameter in the diameter list
so my questions are
1) how can i upload a list of values data file in to solver?
2)and how to write expressions to calculate the value for each data value in the above uploaded list ?

waiting for your valuable suggestions ....

thanks
krish

ghorrocks · May 5, 2012, 08:08

Read the documentation on this issue. But in general it is a good idea to move the boundary further down stream when this warning occurs.

It has been a while since I set particle distributions like that but I recall it can be done. Have a read of the documentation.

April 30, 2012, 10:58	defining-particle size distribution-in cfx	#1
harry39 New Member krish Join Date: Apr 2012 Posts: 5 Rep Power: 14	hello all, i am doing two phase flow simulations in ansys cfx.while initialization of boundary conditions at inlet in particle behaviour tab..i have to mention the particle size distribution with a user specified discrete diametr distribution function.i have functions for both mass fraction and number fraction as a function of diameter. how can i insert the diameter list...? and mass fraction list & number fraction list.....as a function of diameter..? advance thanks krish

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April 30, 2012, 20:52		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	This is covered in the tutorials on particle flows. And please do not PM me when you have already posted the identical question on the forum.

May 1, 2012, 20:00		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	The tutorials are in the help files, and the example files are in <CFX_ROOT>/examples

May 4, 2012, 07:47		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	It is not an error, it is a warning. It simply means you are getting backflow at your outlet. If it does not go away you should move your outlet downstream.

May 5, 2012, 08:08		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Read the documentation on this issue. But in general it is a good idea to move the boundary further down stream when this warning occurs. It has been a while since I set particle distributions like that but I recall it can be done. Have a read of the documentation.