LBT Air Flow Network Simulation

[KantoHiro]

LBT is so great simulation tool!
I have great result by using this tool!

by the way i try to use Air flow Net work
we can get how wind influence building energy
but can we input specific Wind Pressure Coefficient Value?
we can get Wind Pressure Coefficient Value by CFD or some standard

If you know the way or some update , please tell me11

[SaeranVasanthakumar]

@KantoHiro

At this point you cannot input custom wind pressure coefficients to the LBT components. Right now Ladybug uses a simplified method in EnergyPlus that approximates your building geometry as a bounding box and solves the wind pressure coefficients for this simpler geometry.

For my students, I usually reccomend that they check EP’s autocalculations by mapping the simulated wind pressure gradient to the facade, using the AFN Linkages Node 1 to Node 2 Pressure Difference output (see below). For more complicated geometries you will clearly see where the bounding box assumptions begins to fail.

[chris]

Hi @KantoHiro ,

Invariably, the input for custom wind pressure coefficients is going to be complex since you’ll need several CDF simulations and a lot of postprocessing of those CFD results to get wind pressure coefficients for every window at each cardinal direction.

If you managed to do all this, then you can write an OpenStudio measure that would parse your CSVs of all your wind pressure coefficients and then overwrite the parts of the Honeybee AFN to supply the wind pressure coefficient to EnergyPlus. The key parts that you would have to change in the Honeybee-Exported AFN are:

• Change the wind pressure coefficient type for the AirflowNetworkControl to be Input instead of SurfaceAverageCalculation.
• Add your Wind Pressure Coefficients as a WindPressureCoefficientArray
• Assign those coefficient arrays to the SimpleOpening objects that represent the windows in the AFN.

… or you could just use the built-in SurfaceAverageCalculation as Saeran suggests, which is good enough for cases where you don’t have super-complex surroundings.

[KantoHiro]

@SaeranVasanthakumar

At this point you cannot input custom wind pressure coefficients to the LBT components. Right now Ladybug uses a simplified method in EnergyPlus that approximates your building geometry as a bounding box and solves the wind pressure coefficients for this simpler geometry.

For my students, I usually reccomend that they check EP’s autocalculations by mapping the simulated wind pressure gradient to the facade, using the AFN Linkages Node 1 to Node 2 Pressure Difference output (see below). For more complicated geometries you will clearly see where the bounding box assumptions begins to fail.

@chris @SaeranVasanthakumar
Thanks a lot and Sorry for
Sorry for the delay in replying.
I see that Saeran is right, it is easy to analyze 16 directions in CFD, although it takes a long time, but I think it is better to simplify it for the first study.
If I can do it with CFD, it would be better to rewrite it with Openstudio.
I’ll give it a try.
Thank you very much for your help!