# Normalisation by T for Stokes preconditioning

**URL:** <https://discourse.channelflow.ch/t/normalisation-by-t-for-stokes-preconditioning/41>\
**Category:** Development\
**Created:** [October 30, 2018, 3:47pm UTC](https://discourse.channelflow.ch/t/normalisation-by-t-for-stokes-preconditioning/41 "2018-10-30T15:47:20Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jlangham](https://avatars.discourse-cdn.com/v4/letter/j/a88e4f/32.png) [@jlangham](https://discourse.channelflow.ch/u/jlangham)\
**Post date:** [October 30, 2018, 3:47pm UTC](https://discourse.channelflow.ch/t/normalisation-by-t-for-stokes-preconditioning/41/1 "2018-10-30T15:47:20Z")

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Hi all,

Currently findsoln and continuesoln (as far as I know) normalise the search residual by T if they are looking for equilibria.

In the case of Stokes preconditioning [(-L) flag] normalisation should also be avoided because for high T (the intended use case is e.g. T \> 10) the pde operator is a T-independent approximation to the steady Navier-Stokes equations. (So if you divide through by T it artificially decreases the search residual.)

I would suggest the following amendment to findsoln.cpp

```
  - const bool Tnormalize = Tsearch ? false : true;
  + const bool Tnormalize = (Tsearch || searchflags.laurette) ? false : true;

```

plus something similar for continuesoln.cpp.

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**Author:** ![mirko.farano](https://yyz1.discourse-cdn.com/flex027/user_avatar/discourse.channelflow.ch/mirko.farano/32/10_2.png) [@mirko.farano](https://discourse.channelflow.ch/u/mirko.farano)\
**Post date:** [November 6, 2018, 2:26pm UTC](https://discourse.channelflow.ch/t/normalisation-by-t-for-stokes-preconditioning/41/2 "2018-11-06T14:26:26Z")

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Thank you very much for pointing this out.  
We will fix this issue.  
Mirko