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Variation of output data from Radiance-measure

asked 7 years ago

BORM's avatar

updated 7 years ago

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?

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answered 7 years ago

updated 7 years ago

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.

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

BORM's avatar BORM  ( 7 years ago )

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Asked: 7 years ago

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Last updated: May 30 '17