Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question
2

Variation of output data from Radiance-measure

asked 2017-05-30 09:57:39 -0600

BORM gravatar image

updated 2017-08-05 07:31:00 -0600

I'm actually working with Radiance measure in OpenStudio (V 1.14).

I just realize that if I run the same model, three time for example, there are fluctuations from Illuminance points data in the map.ill file. First, I try different models and different Weather files but I got the same problem.

There is an example of the fluctuation for 3 simulations.

Time    Sim. 1 (Lux)    Sim. 2 (Lux)    Sim. 3 (Lux)    Variation (Lux)
8:00      15981          15907.6          16041.5         133.9
9:00      21595          21754.4           21698          159.4
10:00     24567          24767.6          24721.5         200.6
11:00     21870.1        21983.2          22302.8         432.7
12:00     11636.3         11432           11490.5         204.3
13:00     4564.3           4608            4567.9          43.7
14:00     3273.3          3242.7           3267.2          30.6
15:00     2175.4          2155.4           2178.5          23.1

Since the parameters of the model are the same, is the variation of the results are made by Radiance measure calculations?

Do you have any suggestions?

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted
3

answered 2017-05-30 10:54:01 -0600

updated 2017-05-30 11:03:36 -0600

Radiance uses a stochastic process to determine the light transport in a space, not a deterministic one; you will almost always get some variance in your results. The more rigorous the calculation (i.e. "higher" simulation parameters, spawning more rays), the smaller the degree of variation. Your results above seem pretty stable to me; instead of plotting the variation in terms of lux, look at it as a percentage. You're generally at less than one percent -- actually pretty good.

edit flag offensive delete link more

Comments

Thank you! Very helpful! I'm going working on it!

BORM gravatar imageBORM ( 2017-05-30 11:27:39 -0600 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

 

Question Tools

1 follower

Stats

Asked: 2017-05-30 09:57:39 -0600

Seen: 52 times

Last updated: May 30 '17