[TRNSYS-users] calculation error?
Stefan de Kool
S.deKool at chri.nl
Wed Mar 28 07:11:39 PDT 2007
Dear all,
I'm having a problem with a simple calculation (see attached files). I have
3 inputs, c0, c10 and c20, which are defined by type 14. I run the following
calculation:
c-pred= teller / noemer, with teller = (c10^2 - c0*c20) and noemer = (2*c10
- (c0+c20)).
When I output these values, I get strange differences compared to values
calculated in XL (see attached xl-file). At the first 48 timesteps
everything goes fine with relative errors on the order of 10^-6, but from
the 49th step on, errors on the order of 10^-4 occur. Strangly these occur
only at the uneven timesteps. The errors occur only in teller and noemer but
are, I suppose, levelled out after division.
Can anyone help with this? I suspect it has something to do with
rounding-off errors but I can not find the exact cause. The only change I
see in the input values at step 49 is that c10 changes from below 10^3 to
above 10^3.
I tried decreasing the tollerances and also using Powell instead of
Succesive, to no avail. When I change the timebase from 100h to 1000h (also
for the type 14), the errors occur at different timesteps and different
rates.
Thanks in advance,
Stefan de Kool
Cauberg-Huygen Raadgevende Ingenieurs B.V.
Bezoekadres: Boterdiep 48, 3077 AW ROTTERDAM
Postadres: Postbus 9222, 3007 AE ROTTERDAM
Telefoon: +31 (0)10-2443638
Fax: +31 (0)10-425 44 43
http://www.chri.nl
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20070328/e50d54e1/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 5894 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20070328/e50d54e1/attachment-0001.jpeg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: model.TPF
Type: application/octet-stream
Size: 53341 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20070328/e50d54e1/attachment-0002.obj>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: output1.txt
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20070328/e50d54e1/attachment-0001.txt>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Project1.dck
Type: application/octet-stream
Size: 5838 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20070328/e50d54e1/attachment-0003.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: analysis.xls
Type: application/vnd.ms-excel
Size: 56832 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20070328/e50d54e1/attachment-0001.xls>
More information about the TRNSYS-users
mailing list