# different mass flow rates

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 February 14, 2005, 05:35 different mass flow rates #1 michael Guest   Posts: n/a Sponsored Links hi anybody! I have problem with calculating the mass flow rate. I used the Turbo postprocessing panel for calculation mass flow rate (oultet) boundary. I was suprised when I calculated the mass flow rate using 'report-> surface integrals'. Calculated mass flow rate: Density(average)*Velocity(radial,average)*Area =mass flow rate. Obtained mass flow rate using area- and mass-weighted average report types gave different m.f.rates than one calculated by turbo post. panel. Is my formulation of m.f.rate wrong, or just turbo post. panel has some bugs. Please help, I don't know which value is correct.

 February 14, 2005, 13:48 Re: different mass flow rates #2 Robin Guest   Posts: n/a Hi Micheal, You should not average the values first. Rather, calculate the sum of Density*Velocity_normal*Area_normal. Fluent should have a function to calculate Mass Flow's directly, since the IP mass flows will differ slightly from this calculation. -Robin

 February 15, 2005, 04:24 Re: different mass flow rates #3 michael Guest   Posts: n/a Thanks a lot Robin. You have right. I have one question more: My problem is unsteady, so I would like to save mass flow rates through the inlet and outlet boundaries every time step. It is easy to save some quantities using solve->monitors->surface-> and so on… But there is no possibility to monitor mass flow rate through the selected zone. Is there any easy possibility to do that without writing UDF (unfortunately T am not so familiar in UDFs)? best regards

 February 15, 2005, 21:47 Re: different mass flow rates #4 Robin Guest   Posts: n/a I haven't the foggiest idea of how to do this in Fluent. I can tell you the expression for CFX-5, but that isn't going to help you much. Regards, Robin

 February 21, 2005, 04:48 Re: different mass flow rates #5 George Guest   Posts: n/a I think that you just need to use a Custom Field Function, not a UDF. Regards George

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