# Solving a no linear equation of the Spalart-Allmaras model

**URL:** <https://fenicsproject.discourse.group/t/solving-a-no-linear-equation-of-the-spalart-allmaras-model/15199>\
**Category:** dolfinx\
**Created:** [July 9, 2024, 12:41pm UTC](https://fenicsproject.discourse.group/t/solving-a-no-linear-equation-of-the-spalart-allmaras-model/15199 "2024-07-09T12:41:06Z")\
**Posts on this page:** 1\
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**Author:** ![francesco-ballarin](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@francesco-ballarin](https://fenicsproject.discourse.group/u/francesco-ballarin)\
**Post date:** [July 9, 2024, 5:11pm UTC](https://fenicsproject.discourse.group/t/solving-a-no-linear-equation-of-the-spalart-allmaras-model/15199/2 "2024-07-09T17:11:00Z")

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Please read [Read before posting: How do I get my question answered?](https://fenicsproject.discourse.group/t/read-before-posting-how-do-i-get-my-question-answered/21) . The code you posted isn’t reproducible.

I would first of all try with a direct solver. Are you sure that you can use `cg` to solve with the jacobian matrix on the left-hand side? Looking at the expressions you have in `fv1`, I wouldn’t vouch that `J` is symmetric positive definite.

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