# Comparing SIMSCALE with some handbook and webpages

**URL:** https://www.simscale.com/forum/t/comparing-simscale-with-some-handbook-and-webpages/98162
**Category:** Product Feedback
**Created:** [March 13, 2024, 8:01pm UTC](https://www.simscale.com/forum/t/comparing-simscale-with-some-handbook-and-webpages/98162 "2024-03-13T20:01:25Z")
**Posts on this page:** 1
**Showing post:** 10

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### Author: ![jjansman](https://www.simscale.com/forum/letter_avatar/jjansman/32/5_5575768a8748004e209b776fc1b2916d.png) [@jjansman](https://www.simscale.com/forum/u/jjansman)
#### Post date: [April 27, 2024, 6:56pm UTC](https://www.simscale.com/forum/t/comparing-simscale-with-some-handbook-and-webpages/98162/10 "2024-04-27T18:56:15Z")

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> [@fvgool](#):
>
> - the height of the total domain should be higher. that cost 732 paper I mentioned gives some better insights. (try 4x higher)

Think this is indeed not correct what I had. I used a flow region height of 40m (2.5H) and my object of interest was H=16m high. So now I changed the flow region height to 100m (6H).

> [@fvgool](#):
>
> - the roughness on the bottom should be set according to the help of simscale (constant = 1)

I used 10m, more or less 20times the z0. By the way I see this also a (lower) recommendation for terrain scale 6 by SIMSCALE: a factor of 10.

> [@fvgool](#):
>
> - boundary layers should be added to the bottom. Simscale fails to do that automatically.

I don’t understand this point: I set the roughness height in the boundary ‘Custom’. Anyway I use a boundary layer for all surfaces of the flow region. Perhaps I misunderstand this point?

> [@fvgool](#):
>
> - the mesh has a poor non-orthogonality, increase the correctors for that. (and / or improve the mesh)  
> (- and use the pot-flow initialisation, is faster)

If I look in the Mesh quality file I see:  
_nonOrthogonality_  
_Acceptable range: 0 to 88_  
_min: 0_  
_max: 89.96142835721949_  
_average: 15.115932162422554_  
_standard deviation 11.87045328471216_  
_median: 14.786002566388524_  
_99.9-th percentile: 56.65718636249987_  
_99.99-th percentile: 67.50480604953317_  
_99.999-th percentile: 77.50601308919153_  
So this looks all ok, correct? By the way what is: ‘pot-flow initialisation’?

> [@fvgool](#):
>
> - overall, I would not use the default simscale meshing, it is not good. Fill in manual sizes for all you mesh work.

At this moment I used the default meshing, the manual of Fineness setting did not work for me (all setting above 7.5 and 10 cause same issues). It looks the the Roughness height of ground is a reason for terminated Runs. A Roughness height of 1m works mostly, but a 3, 5 or 10m Roughness height causes _Gauge pressure field started diverging_ (see another mail thread: [Gauge pressure field started diverging - #9 by jjansman](https://www.simscale.com/forum/t/gauge-pressure-field-started-diverging/98319/9) ).

Thanks for your help. I am slowly getting there.

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