# Streamline laplace equation

**URL:** https://community.freefem.org/t/streamline-laplace-equation/833
**Category:** General Discussion
**Created:** [March 4, 2021, 7:13pm UTC](https://community.freefem.org/t/streamline-laplace-equation/833 "2021-03-04T19:13:29Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![mrbenson](https://avatars.discourse-cdn.com/v4/letter/m/d07c76/32.png) [@mrbenson](https://community.freefem.org/u/mrbenson)
#### Post date: [March 4, 2021, 7:13pm UTC](https://community.freefem.org/t/streamline-laplace-equation/833/1 "2021-03-04T19:13:29Z")

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Hello,

I’m back to compute streamlines function using the vorticity equation but it seems that something is wrong…  
It’s a very basic test case solving laplacian problem on a square. The streamlines are not parallel to the vector flux, so not orthogonal to the isoline…

Any idea ? Thanks for helping.

[temp.edp](https://community.freefem.org/uploads/short-url/yovSYkDnQATGg573XJ8P8UvsI0P.edp) (753 Bytes)

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### Author: ![aszaboa](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/aszaboa/32/2918_2.png) [@aszaboa](https://community.freefem.org/u/aszaboa)
#### Post date: [March 4, 2021, 9:41pm UTC](https://community.freefem.org/t/streamline-laplace-equation/833/2 "2021-03-04T21:41:24Z")

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Hi!  
To me it seems that changing line 3 to  
`fespace Ph(Th, P2);`  
fixes your issue.

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### Author: ![mrbenson](https://avatars.discourse-cdn.com/v4/letter/m/d07c76/32.png) [@mrbenson](https://community.freefem.org/u/mrbenson)
#### Post date: [March 4, 2021, 9:48pm UTC](https://community.freefem.org/t/streamline-laplace-equation/833/3 "2021-03-04T21:48:51Z")

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I tried P2 interpolation but still the same

The streamlines are not parallel to the vector flux.

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/1X/b4a495fa92a02b46e80376160682183b9c1c9fb3.png)

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### Author: ![mrbenson](https://avatars.discourse-cdn.com/v4/letter/m/d07c76/32.png) [@mrbenson](https://community.freefem.org/u/mrbenson)
#### Post date: [November 26, 2021, 10:58am UTC](https://community.freefem.org/t/streamline-laplace-equation/833/4 "2021-11-26T10:58:16Z")

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Hello

I’m back to this problem of streamlines but i really can’t obtain parallel streamlines to the vector flux…