code_saturne User's Forum

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

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

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

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

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

best regards,

Houda