# How to handle advection-term involving two unknows?
**URL:** https://community.freefem.org/t/how-to-handle-advection-term-involving-two-unknows/3411
**Category:** General Discussion
**Created:** [July 24, 2024, 11:56pm UTC](https://community.freefem.org/t/how-to-handle-advection-term-involving-two-unknows/3411 "2024-07-24T23:56:57Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Hemanta822](https://community.freefem.org/u/Hemanta822)
#### Post date: [July 24, 2024, 11:56pm UTC](https://community.freefem.org/t/how-to-handle-advection-term-involving-two-unknows/3411/1 "2024-07-24T23:56:57Z")
Hello All,
I am trying to implement a temperature equation in the fluid system. I have a term (u \dot \nabla T) that couples velocity and temperature in the temperature equation. How can I handle such a term? Any help or direction would be greatly appreciated. Thank you so much!
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### Author:  [@localhost](https://community.freefem.org/u/localhost)
#### Post date: [August 12, 2024, 2:02am UTC](https://community.freefem.org/t/how-to-handle-advection-term-involving-two-unknows/3411/2 "2024-08-12T02:02:07Z")
You can solve NS equation first, then the u is known. Or you can use newton method to solve the coupled u-T problem
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### Author:  [@Walid](https://community.freefem.org/u/Walid)
#### Post date: [August 19, 2024, 5:56pm UTC](https://community.freefem.org/t/how-to-handle-advection-term-involving-two-unknows/3411/3 "2024-08-19T17:56:11Z")
what is Newton method ?
could you share a reference to simply explain