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-   -   Problem with plotting the Massflow in 2D-Axisymmetric (http://www.cfd-online.com/Forums/star-ccm/103550-problem-plotting-massflow-2d-axisymmetric.html)

 Bando June 20, 2012 11:10

Problem with plotting the Massflow in 2D-Axisymmetric

Hello :)

i'm simulating a venturi nozzle. because of it's axisymmetric geometrie i'm only simulating it in 2D but with the centerline beeing an axis i choose the axisymmetric option instead of just 2D.

now for the problem i'm having:
i want to calculate the massflow at the throat. therefore i inserted a derived parts -> plane at the right location.
when i create a massflow report at the plane it computes me massflows that are about 6 times smaller than the measured ones.
when i define my own massflow user field function as density*velocity*(throat-cross-section-area) and plot that in an X-Y Plot with the centerline representing the X-Axis und my own massflow as the Y-Axis it should plot me the right massflow at the location of the throat. but this time i get an massflow that is about 3 times higher than the measured one.

so can anyone tell me what i'm doing wrong? ore even better how to get the right massflow? :)

 Bando June 21, 2012 05:09

ok, solved the problem...the massflow measured with my own user field function is exactly by that amount higer by witch i scaled my geometrie with star ccm.

so the imported geometrie had ha diameter at the throat of 5mm, i scaled it down to 1,5mm so the scaling faktor is about 3,3. now if i divide my massflow by 3,3 i get the right result.

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