# Axial compressor simulation - Max iterations reached

**URL:** <https://www.simscale.com/forum/t/axial-compressor-simulation-max-iterations-reached/81234>\
**Category:** Project Support\
**Created:** [December 9, 2017, 4:10pm UTC](https://www.simscale.com/forum/t/axial-compressor-simulation-max-iterations-reached/81234 "2017-12-09T16:10:51Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![JacksonEmpey](https://www.simscale.com/forum/user_avatar/www.simscale.com/jacksonempey/32/17296_2.png) [@JacksonEmpey](https://www.simscale.com/forum/u/JacksonEmpey)\
**Post date:** [December 9, 2017, 4:10pm UTC](https://www.simscale.com/forum/t/axial-compressor-simulation-max-iterations-reached/81234/1 "2017-12-09T16:10:51Z")

</div>

I’ve been trying the get the hang of SimScale over the past few days by trying to do some fluid dynamics analysis on an axial compressor, I’ve tried 3 different geometries, tonnes of different meshes, and a whole lot of changes to the numerics but I keep getting a ‘max iterations reached’ error, the residual plot has changed as I’ve tried more fixes but currently only my epsilon residual is decreasing. No simulation has passed 3% yet.

Trying to model an axial compressor (Originally I used moving walls but I dropped it since I figured they may have been giving my ‘max iterations’ issues)  
Inlet → 40m/s air flow  
Outlet → 15bar  
Compressible  
Air

I feel like there’s one little obvious thing I’m doing wrong but I’ve changed the other relaxation factors as recommended by other tutorials. If anyone could give it a look I would really appreciate it.

Originally I was having errors with my epsilon residual being the only one not decreasing but as in the failed ‘run 1’ now epsilon is the only residual that is decreasing.  
Run 1 is a failed run using k-epsilon  
Run 2 is a quick run that I’m doing now, the convergence plot shows that It will likely fail

Also just a heads up this isn’t my can file, I got it form the link in the description

> **[Compressor CFD by JacksonEmpey | SimScale](https://www.simscale.com/projects/JacksonEmpey/compressor_cfd/)**
>
> CAD obtained from https://grabcad.com/library/radial-compressor-2 | Simulation project by JacksonEmpey

Thanks guys

---

<div class="post-metadata">

**Author:** ![jousefm](https://www.simscale.com/forum/user_avatar/www.simscale.com/jousefm/32/34908_2.png) [@jousefm](https://www.simscale.com/forum/u/jousefm)\
**Post date:** [December 9, 2017, 4:19pm UTC](https://www.simscale.com/forum/t/axial-compressor-simulation-max-iterations-reached/81234/2 "2017-12-09T16:19:49Z")

</div>

Hi @JacksonEmpey!

First of all you are using a tet-dominant mesh but you have to use SnappyHexMesh (Hex-dominant parametric) for problems related to fluid dynamics. Furthermore I want to know if you have another model with which we can create a separate rotating zone because the model you provided us with is not closed and cannot be used properly for the simulation (assuming that you want to have a flow inlet, a rotating domain around your impeller as well as a flow outlet.

I think if you fix the issues for the pre-processing step we are on a good way to achieve good results. If you need any further help please let @Anware and me know!

All the best!

Jousef

---

<div class="post-metadata">

**Author:** ![JacksonEmpey](https://www.simscale.com/forum/user_avatar/www.simscale.com/jacksonempey/32/17296_2.png) [@JacksonEmpey](https://www.simscale.com/forum/u/JacksonEmpey)\
**Post date:** [December 9, 2017, 6:00pm UTC](https://www.simscale.com/forum/t/axial-compressor-simulation-max-iterations-reached/81234/3 "2017-12-09T18:00:11Z")

</div>

Thank you! I’m in the middle of exams now but when I have a minute I’ll give it a try!  
Much appreciated!