# PyFR simulating NACA0021 airfoil in deep stall

**URL:** <https://pyfr.discourse.group/t/pyfr-simulating-naca0021-airfoil-in-deep-stall/438>\
**Category:** General\
**Created:** [16 July 2021 08:02 UTC](https://pyfr.discourse.group/t/pyfr-simulating-naca0021-airfoil-in-deep-stall/438 "2021-07-16T08:02:17Z")\
**Posts on this page:** 1\
**Showing post:** 18

<div class="post-metadata">

**Author:** ![hwtang](https://avatars.discourse-cdn.com/v4/letter/h/a87d85/32.png) [@hwtang](https://pyfr.discourse.group/u/hwtang)\
**Post date:** [18 July 2022 07:41 UTC](https://pyfr.discourse.group/t/pyfr-simulating-naca0021-airfoil-in-deep-stall/438/18 "2022-07-18T07:41:05Z")

</div>

Hi @FedericoCipolletta ,

Thank you very much for your reply. I have tried to remove `min-fact` and `max-fact`, but still got the same error.

Regarding the `openmp` backend, it really makes me crazy. Whether I use or remove the following command, I get the same error (`RuntimeError: Minimum sized time step rejected`).

```auto
[backend-openmp]
cc = gcc
cblas-mt = libmkl_rt.so
gimmik-max-nnz = 8192

```

I also failed to use `openmp` as backend to run the example case (see [here](https://pyfr.discourse.group/t/failed-to-run-example-cases-using-openmp-as-backend/649/2), please), and I got another error.

Things are really weird. I am not sure whether the `RuntimeError: Minimum sized time step rejected` error in this NACA0021 case is caused by the same reason as the [example case](https://pyfr.discourse.group/t/failed-to-run-example-cases-using-openmp-as-backend/649/2).

Besides the `min-fact` and `max-fact`, is there any other difference between the config you managed to run and mine?

Thank you for your help.

---

_[View the full topic](https://pyfr.discourse.group/t/pyfr-simulating-naca0021-airfoil-in-deep-stall/438)._