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Old   April 7, 2013, 04:55
Default negative mass flow rate...!!!!
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Sumeet Kotak
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hello friends,

I am working on Species transport model.

I am facing problem like negative mass flow rate..!!!
i had defined custom field variable

mass deposited
of particular species = density*area*velocity*mass fraction of that species


i measure mass deposited over 15 parallel holes at the height of 150mm from the evaporating surface.

holes arrangement over the evaporating surface

1 2 3 4 5
6 7 8 9 10
11 12 13 14 15

I am getting highest deposition at no. 8 according to research paper which I am referring and i had written surface monitor file using report type sum.

My problem is that
first I got increasing positive mass flow rate showing positive sign and than suddenly decreasing than increase value again but showing negative sign...!!
what its mean... ??

my material is getting continuously evaporated...

please replay..

thanks in advance
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Old   April 7, 2013, 14:14
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Quote:
Originally Posted by sumeet kotak View Post
My problem is that
first I got increasing positive mass flow rate showing positive sign and than suddenly decreasing than increase value again but showing negative sign...!!
what its mean... ??
Not sure which solver you're using, but negative mass flow rate means mass is flowing out of your domain.
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Old   April 7, 2013, 14:32
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Sumeet Kotak
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thanks jrdch

I am using pressure based solver
velocity formulation absolute
transient analysis

actually my geometry is a cylindrical chamber n in chamber at height of 150 mm I placed crucible n material which is to be evaporated put in the crucible n material getting evaporated by application of electron beam and 150 mm above I put substrate containing 15 holes at equal distance. the size for crucible is 30 diameter n 3 height n for substrate is 120*120 contains 15 holes of 14 mm diameter n chamber diameter is 400 mm n height is 700mm.

as I explain above there is. no chances of mass going outside the chamber n there is no any significance shown in contour of chamber that shows mass going out of chamber.

may be u r right but in my case that is not possible as I observed.

is there any another reason ...?
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Old   April 7, 2013, 14:34
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Can you post a picture of what your domain/model looks like?
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Old   April 7, 2013, 15:13
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Sumeet Kotak
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I am unable to upload here can u give me ur mail id.
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Old   April 7, 2013, 15:18
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You can upload to img.ur and link to it here.
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Old   April 7, 2013, 15:46
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Sumeet Kotak
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Quote:
Originally Posted by jdrch View Post
You can upload to img.ur and link to it here.
unfortunately I have no computerized drawings with me so I attend hand made drawing hope u can understand.

please find attachments.
thanks
Attached Images
File Type: jpg rps20130408_012522.jpg (18.8 KB, 15 views)
File Type: jpg rps20130408_012435.jpg (25.4 KB, 17 views)
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