# Convergence issues incompressbile 2d channel flow

**URL:** <https://pyfr.discourse.group/t/convergence-issues-incompressbile-2d-channel-flow/195>\
**Category:** General\
**Created:** [8 February 2018 15:10 UTC](https://pyfr.discourse.group/t/convergence-issues-incompressbile-2d-channel-flow/195 "2018-02-08T15:10:14Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Hendrik](https://avatars.discourse-cdn.com/v4/letter/h/839c29/32.png) [@Hendrik](https://pyfr.discourse.group/u/Hendrik)\
**Post date:** [8 February 2018 15:10 UTC](https://pyfr.discourse.group/t/convergence-issues-incompressbile-2d-channel-flow/195/1 "2018-02-08T15:10:14Z")

</div>

Dear PyFR-Developers,  
I’m trying to simulate an incompressbile turbulent 2d channel flow at Re=10000 (L=10D, D=0.016m, u\_mean=0.6275, nu=1e-6, 561 Elements). I provided a simple 1/7-power-law velocity profile as an inlet condition and an arbitary pressure of 1 at the outlet, which should not matter as it is an incompressible case.

Unfortunately however I play around with the ac-factor (varying from 1-10\*u\_mean), the timestep and the pseudo-timestep the simulation blows. I attached my initialisation files. Do you have any hints what could be the matter?  
Kind Regards,  
Hendrik

[pipe\_2d.msh](https://pyfr.discourse.group/uploads/short-url/t3xdRrijrNokYYjLEGU9mekmOEL.msh) (36.1 KB)

[pipe\_2d.ini](https://pyfr.discourse.group/uploads/short-url/4LA93tNnMHuQ1mtZOZhgbmJgZPU.ini) (1.54 KB)