# Integrate variables problem

**URL:** https://discourse.paraview.org/t/integrate-variables-problem/17110
**Category:** ParaView Support
**Created:** [August 19, 2025, 6:54pm UTC](https://discourse.paraview.org/t/integrate-variables-problem/17110 "2025-08-19T18:54:35Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Lasher326](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/l/f475e1/32.png) [@Lasher326](https://discourse.paraview.org/u/Lasher326)
#### Post date: [August 19, 2025, 6:54pm UTC](https://discourse.paraview.org/t/integrate-variables-problem/17110/1 "2025-08-19T18:54:35Z")

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I am trying to calculate the flow rate of oil in a 3-phase flow from OpenFOAM at the outlet. It is not correct so I tried it at the inlet where I know the flow rate of water. I used the following filters:

Cell size ==\> Calculator ==\> Integrate variables

The calculator formula is area_U\_water.x_alpha.water

The actual flow rate is 1.2 E-3 m3/s

The flow rate calculated following integration is 1.83 E-7.

If I sum the column in the spreadsheet from the Calculator filter I get 1.16 E-3 (close to the known value, 3.3% different), so it appears that the Calculator filter is correct but the Integrate Variables filter is not.

Any suggestions?