# Determine what part of a source leaves an outflow point
**URL:** https://discourse.paraview.org/t/determine-what-part-of-a-source-leaves-an-outflow-point/1219
**Category:** ParaView Support
**Created:** [February 1, 2019, 7:28am UTC](https://discourse.paraview.org/t/determine-what-part-of-a-source-leaves-an-outflow-point/1219 "2019-02-01T07:28:21Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@MarkB](https://discourse.paraview.org/u/MarkB)
#### Post date: [February 1, 2019, 7:28am UTC](https://discourse.paraview.org/t/determine-what-part-of-a-source-leaves-an-outflow-point/1219/1 "2019-02-01T07:28:21Z")
Hi all,
I have an incompressible flow simulation from openfoam where I have 2 inlets and 2 outlets.
How can I determine what part of inlet 1 is leaving though outlet 2?
Is there a tracer/filter I can use for this?
Thanks,
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 1, 2019, 9:44am UTC](https://discourse.paraview.org/t/determine-what-part-of-a-source-leaves-an-outflow-point/1219/2 "2019-02-01T09:44:40Z")
Here is a way, using the StreamTracer :
- Open your dataset, Apply
- Select the inlet points
- Add an ExtractSelection filter, Apply
- Set your dataset as the active source
- Add a StreamTracerWithCustomSource filter,
- Set the extract selection as the seed source
- Configure the StreamTracer accordingly to your data, Apply
---
### Author:  [@MarkB](https://discourse.paraview.org/u/MarkB)
#### Post date: [February 8, 2019, 7:42am UTC](https://discourse.paraview.org/t/determine-what-part-of-a-source-leaves-an-outflow-point/1219/3 "2019-02-08T07:42:51Z")
Mathieu,
Thanks for the reply I’ll give it a go.