Code_saturne setting for simulation on urban case

[HBELG]

Hello,
I am searching for opinions about the basic setting to run simulations in atmospheric flow on an urban case (squares of 800m/800m), I want to share with you what setting I am applying:

- turbulence model: k-epsilon steady flows
- No thermal scale physical properties (no changement for what is put by default)
- boundary conditions generally:
// upper part and lateral part of the vein are symmetric // buildings roof (wall - smooth) building's wall (wall - roughness height 0.0025) // down the surface of the vein (wall without roughness)

- INLET: logarithmic profile + turbulence formula relaxation of pressure increase = 1.0 velocity - Pressure algorithms: Simplec
- nb of iteration: (300 sometimes 900)

- I include a set of mounting points and I do generally a parallel computing on 4 cores

- Number of cells: 3114820

I have 3 questions:
1/ Do I have to check or change another parameter in code Saturne according to the atmospheric flow?

2/ If I want to use a power law for velocity, do I have to change the formula of the turbulence or I can use the same for the logarithmic profile

3/ For the monitoring points I am interested in the evolution of their velocity, but what I get (velocity x, velocity y, velocity z), is there a way to get the magnitude velocity (vitesse résultantes)?
4/ For the boundary condition is there a way to put "slip boundary condition", what is the difference between slip condition and symmetry conditions?

I will be so glad for any opinion or discussion about the setting, thanks for any help
Best regards

Houda

[Yvan Fournier]

Hello,

I'll let colleagues working on the atmospheric models answer most questions, but I can answer a few:

1/ Are you using the atmospheric model ? I'd recommend this

3/ Using the new profile system (currently only usable using user functions, in cs_user_postprocess.c) you can do this.

4/ Symmetry an slip are the same to my knowledge

Regards,

Yvan

[HBELG]

Please can you explain to me what is the atmospheric model, because so far I am using the recommendations of the COST 2007 (Franck et al 2007) to set the parameters in code _saturne in a way to be alike the atmospheric conditions for micro-scale,

What is exactly the atmospheric model?

Best regards,

Houda

[Yvan Fournier]

Hello,

There are multiple atmospheric models (dry air, humid air, ... pollutant chemistry)... The associated documentation may be based more on articles than the main Code_Saturne documentation, so there may be missing pieces there, but I can check with the developers of this version if they can provide a few bibliographical notes in case you are missing info.

I am not familiar with COST 2007 so do not know how it relates to the model in Code_Saturne.

Regards,

Yvan

[HBELG]

Thanks a lot for your help, and yes i would like to have any notes that may help,

best regards,

Houda