[TRNSYS-users] Type 9 data reader

[Jeff Thornton]

> i tried to read a data file with a 1/4 h time interval of average data
>   in a 1 min simulation. If I set "Averareous or instantenous value" to
>   "average" I got some wrong curve and the values seemed to be mirrored
>   on the x axis. Can anybody help me to better understand the
>   behanviour of type 9?

You have to be very careful when you're using average values over the
timestep - remember Type 9 uses a linear interpolation scheme.  As David
suggested, using the wrong initial value can cause problems.  Take the
very simple case of y=1 for all time.  The average values of y for each
interval would then be identically 1.  If you provided an initial value of
0 to the model however, you would get the following result:

Time = 0, Value = 0 (initial condition)
Time = 1, Value = 2 (starts at 0, average=1, therefore endpoint = 2)
Time = 2, Value = 0 (starts at 2, average=1, therefore endpoint = 0)

This trend would continue and you would have an oscillating solution with
time.

I would suggest you review your initial values carefully.

Jeff


Jeff Thornton
President - TESS, LLC

22 North Carroll Street - Suite 370
Madison WI 53703 USA

Phone: 608-274-2577
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