# Cylindrical coordinate for flow simulation
**URL:** https://community.freefem.org/t/cylindrical-coordinate-for-flow-simulation/1941
**Category:** General Discussion
**Created:** [August 12, 2022, 6:34am UTC](https://community.freefem.org/t/cylindrical-coordinate-for-flow-simulation/1941 "2022-08-12T06:34:07Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@zese](https://community.freefem.org/u/zese)
#### Post date: [August 12, 2022, 6:34am UTC](https://community.freefem.org/t/cylindrical-coordinate-for-flow-simulation/1941/1 "2022-08-12T06:34:07Z")
Dear all
I want to solve a flow inside a pipe in 3D and I have (r,theta,z) as my coordinate. how I can define d/dtheta or d/dr in freefem?
BR
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### Author:  [@frederichecht](https://community.freefem.org/u/frederichecht)
#### Post date: [August 12, 2022, 11:50am UTC](https://community.freefem.org/t/cylindrical-coordinate-for-flow-simulation/1941/2 "2022-08-12T11:50:02Z")
If you are in 3d you are using x,y,z but ca can recall as r,theta, z
when of domain is a box [0,R]x[0,2\*pi],[Zmin,ZMax]
with periodic boundary condition on theta.
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### Author:  [@Markov](https://community.freefem.org/u/Markov)
#### Post date: [March 30, 2023, 1:44pm UTC](https://community.freefem.org/t/cylindrical-coordinate-for-flow-simulation/1941/3 "2023-03-30T13:44:06Z")
Hello, did you succeed in applying a periodic boundary condition on theta?
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### Author:  [@zese](https://community.freefem.org/u/zese)
#### Post date: [April 2, 2023, 7:07am UTC](https://community.freefem.org/t/cylindrical-coordinate-for-flow-simulation/1941/4 "2023-04-02T07:07:50Z")
Hi Markov,
Unfortunately no because the subject has changed. I wish you find the answer.