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Old   April 12, 2005, 02:42
Default Converting experimental mass flows into 2D fluent
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Trond G. Grüner
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I am using the Mass Flow Inlet Boundary Conditions and Injections. How can I convert experimental mass flows into 2D fluent values? The experimental inlet area is (0.02 m * 0.125 m =) 0.0025 m2. The air mass flow is 0.7 kg/s and the droplet mass flow is 2 kg/s. The width-side (0.02 m) is used as the model side. I think I can convert the air mass flow into a mass flux and use 280 kg/m2s.
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Old   April 12, 2005, 04:56
Default Re: Converting experimental mass flows into 2D flu
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rom
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2D flow are computet like 3D flows by fluent. fluent expands you 2d(xy) model 1m into z direction and solves th resulting 3d flow. to get realistic mass flow rates you could use a hihger mass flow rate correspnding to the new inlet area (0,02 m2) or use 3d model (best option imho).

hope this helps rom
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Old   April 12, 2005, 05:38
Default Re: Converting experimental mass flows into 2D flu
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Trond G. Grüner
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Thank you.

I can use 280 kg/m2s or 5.6 kg/s in fluent, which will represent the experiment. But what about the droplet flow? Is the mass flow (kg/s) in fluent the same as kg/(s*m) form the experiment? The mass flow droplet will then be (2 kg / s / (0.125 m) =) 16 kg/(sm).

What regards do I have to take when using symmetry (not axis symmetry)? When using 280 kg/m2s air flow, the inlet velocity coincides with the realistic velocity. Do I have to do something about the droplet flow?
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Old   April 12, 2005, 08:22
Default Re: Converting experimental mass flows into 2D flu
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rom
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If you use surface as an injection type for your droplets you should scale your droplet massflow rate to get the same loading as in you experiment. With an airflowrate of 5.6kg/s and a loading of 2kg droplets/0.7 kg air the new droplet flowrate should be 16kg/s absolut or 16kg/s/0.125m2=128kg/s/m2.

If you use area specfific massflowrates as bc for symmetric flows you dont need to change them. This is not true for absolute mass flow rates. Lets say you model a pipe with an inlet face area of 1m2 and a flowrate of 5kg/s. the area specific massflow rate is 5kg/s/m2. If you cut the pipe in a half with a symmetry plane the area specefic flow rate remains the same but the absolute flow rate is now 2.5kg/s.

Sorry for my bad english but i hope it helped Rom
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