# Periodic boundary conditions and stream tracer analysis

**URL:** https://discourse.paraview.org/t/periodic-boundary-conditions-and-stream-tracer-analysis/5079
**Category:** ParaView Support
**Created:** [August 11, 2020, 9:58am UTC](https://discourse.paraview.org/t/periodic-boundary-conditions-and-stream-tracer-analysis/5079 "2020-08-11T09:58:10Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![samhughes](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/s/9dc877/32.png) [@samhughes](https://discourse.paraview.org/u/samhughes)
#### Post date: [August 11, 2020, 9:58am UTC](https://discourse.paraview.org/t/periodic-boundary-conditions-and-stream-tracer-analysis/5079/1 "2020-08-11T09:58:10Z")

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Hi there,

I’ve been trying to find a way to do the following, I’ve not found anything online, nor had much success myself and was wondering if anyone had done anything similar, seen a similar problem or knows a good way to approach this.

I’ve got a .vti file containing a solved velocity field for laminar flow in porous media. it’s fairly chunky (for me) approximately 5gb in size. What I’ve done so far is:

- Adjust the velocity by a scale factor (using calculator)
- Take a slice at the entrance using slice and then mask points to select 3000 points from the slice
- stream trace with custom source (using the slice) to get streamlines running through my porous media.

My plan is to export these streamlines to perform various statistical analysis techniques on them (my first issue is how can I export the positions and velocity points of these streamlines).

My main issue however is that the domain is periodic and therefore streamlines are disappearing off the side of my domain. I was wondering if there was an easy way to implement a ‘border’ taking a slab from one side and copying it to the other? I managed to make a slab separately, but I can’t merge the two data sets.

I have access to a HPC if I need to run the calculations in a python script (my computer is struggling with 16gb ram).

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### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [August 11, 2020, 10:40am UTC](https://discourse.paraview.org/t/periodic-boundary-conditions-and-stream-tracer-analysis/5079/2 "2020-08-11T10:40:48Z")

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This is something doable with the LagrangianParticleTracker, but definitely not easy.  
See here for more info :

> **[VTK and ParaView Add Highly Configurable Particle Tracker - Kitware Blog](https://blog.kitware.com/vtk-and-paraview-add-highly-configurable-particle-tracker/)**
>
> Particle trackers and streamlines serve as important tools in multiple scientific domains such as fluid dynamics, thermodynamics, medicine, and biology. Since the creation of the ... Read More

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### Author: ![samhughes](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/s/9dc877/32.png) [@samhughes](https://discourse.paraview.org/u/samhughes)
#### Post date: [August 11, 2020, 10:47am UTC](https://discourse.paraview.org/t/periodic-boundary-conditions-and-stream-tracer-analysis/5079/3 "2020-08-11T10:47:58Z")

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Thanks, I’ll take a look. Worst comes to it I’ll just ignore streamlines that don’t reach the end point, as it’s random packing it shouldn’t add bias… it’s more that it would be nice to ‘do it properly’.