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Mass Flow for 2D

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Old   July 3, 2003, 11:01
Default Mass Flow for 2D
  #1
mahesh
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Hi all,

I have mass flow rate at Inlet. But it is for actual geometry. For solving 2D problem, I have to take the same mass flow rate or different one.

Can anybody suggests.

Thanks in advance.

Mahesh
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Old   July 3, 2003, 11:45
Default Re: Mass Flow for 2D
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ap
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If you're using the 2D solver (not Axi), FLUENT uses a third virtual dimension which is 1 meter long to do calculations.

So, if you want the same flux (kg/(m^2 s)) through your system, you need to change inlet mass flow rate. Just divide your actual mass flow rate by the actual inlet section and then multiply the result by the model section, which is given by the inlet width multiplied by 1 m.

Hope this helps

Hi

ap
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Old   July 4, 2003, 00:27
Default Re: Mass Flow for 2D
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Mahesh
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hi,

Then in that case my mass flux will be more than the actual( as 3rd dimension is 1m). But I have only 2D c/s & dont know about the area. Then how to proceed?

Thanks.

Mahesh
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Old   July 4, 2003, 11:33
Default Re: Mass Flow for 2D
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Mohamed
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Hi mahesh

u have to divide your original mass flow rate [for example: in Kg/s] by the section area of your inlet section. Your unit becomes [Kg /(mēs)]for example. Then, ucompute the area of the virtual section [mē] (multily the edge length on your 2D geometry by 1 m); and u multiplye it by the mass flow rate :

[(Kg /(mēs))* mē]=[Kg /s]

Sorry for my english,

Good Luck
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Old   July 4, 2003, 12:54
Default Re: Mass Flow for 2D
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ap
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Your mass flux (kg/(m^2 s)) stays constant. What changes is the mass flow rate (kg/s).

Call G the mass flux, m_a the actual mass flow rate, Sa the actual section, L the lenght of the edge of your inlet in the 2D model. You have:

G = m_s/S

The mass flow rate you have to use in the model is:

m_model = G * L * 1 m

Hi

ap

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Old   July 11, 2003, 06:32
Default Re: Mass Flow for 2D
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mahesh
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Dear ap,

We have completed trial runs on a 2D geometry. We are facing following problems,

When we keep mass flux same i.e when we impose mass-flux at inlet and pressure at outlet, we are getting very high pressure values at inlet.On the other hand when we give pressure in and pressure outlet bc, we get very less mass flux.

So, exactly what we should look for in 2D analysis, mass flux ? or pressure ?

Thanks, Mahesh
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Old   July 11, 2003, 09:00
Default Re: Mass Flow for 2D
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pws
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If you are really unsure of what the 2D solver is giving you, you could just extrude the 2D mesh a unit distance (keeping cell aspect ratios in mind) and then apply symmetry boundaries on the sides. This should be numerically identical to a 2D calculation.
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Old   October 18, 2009, 20:29
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vishnu
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Thanks a lot guys..I have the same problem. I was looking for solution..this thread really helped.
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