[Radiance-general] perforated lamellas

[Gregory J. Ward]

Hi Friedemann,

I was hoping someone else who knew more about this material might  
respond, but maybe no one does...

If you want an accurate model of this material, you need to use the  
geometric cross-section and the material properties to create an  
analytic estimate of the integrated light transfer.  In other words,  
it ain't easy.  Better still, you would obtain measurements of the  
angular transmission of the material, but this poses an even greater  
challenge.

A couple of years ago, Visarc hired me to create a mathematical model  
of transmission through a grid structure, simulated as rectangular  
holes in a diffuse structure.  The associated calculation is  
contained in grating.cal in the standard distribution.  If your holes  
are oval rather than rectangular, this won't be as accurate, but it  
might be a start.  If your surface is specular and you wish to  
capture the change in specular reflectance with angle, more work is  
needed.

-Greg

> From: "Friedemann Kik" <kik at transsolar.com>
> Date: October 27, 2006 8:20:37 AM PDT
>
> Hi all,
> does anybody knows how I can simulate perforated curved aluminum  
> lamellas? Which material is recommended to get plausible values  
> (for reflection (on aluminum and transmission (through the gaps) by  
> using a sunny and overcast sky in my simulation model? The result  
> should be the illuminance level and respectively Daylight factor  
> inside.
> The lamellas are just rotatable but not movable, the perforation is  
> fixed with 15% (whitout knowing exactly the design of the longish  
> small holes) and should be used like lightshelves in front of heat- 
> protection glass.
>
> Thanks for help!
>
> Friedemann Kik
> kik at transsolar.com