# How to calculate the flow rate

**URL:** https://discourse.paraview.org/t/how-to-calculate-the-flow-rate/806
**Category:** ParaView Support
**Created:** [October 29, 2018, 3:05pm UTC](https://discourse.paraview.org/t/how-to-calculate-the-flow-rate/806 "2018-10-29T15:05:01Z")
**Posts on this page:** 1
**Showing post:** 7

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### Author: ![Kai\_himself](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kai_himself/32/280_2.png) [@Kai\_himself](https://discourse.paraview.org/u/Kai_himself)
#### Post date: [June 21, 2019, 8:34am UTC](https://discourse.paraview.org/t/how-to-calculate-the-flow-rate/806/7 "2019-06-21T08:34:49Z")

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Hey,  
i post it into that topic because its the same topic, if its not ok remove my post and i will start a new topic.

i have to calculate the mass flow over a threshold in a multiphase simulation. I create a slice at the threshold, and then the GenerateSurfaceNormls, but the Glyph are pointing to the side. Why the dont point in the normal direction ?  
There is a screenshot below, showing the glyph.

 ![Normals](https://discourse.paraview.org/uploads/default/original/2X/b/b1cec0804d052cdcc03c23d949f65fea0a84d172.png)

I uploaded two videos, the show the result from the simulation.

  

Is it possible to measure the flow over the threshold ?

Best regards  
Kai

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