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November 29, 2013, 15:48 |
CFX Post Expressions number decimals
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#1 |
New Member
Join Date: Jun 2011
Posts: 5
Rep Power: 15 |
Hi, there,
I am creating an expression in CFX post using the trendline created in the Excel as following: (-798936626.593750*z^6/1[m^6] + 4687121164.076870*z^5/1[m^5] - 11450097996.080200*z^4/1[m^4] + 14908481102.838800*z^3/1[m^3] - 10912008484.852500*z^2/1[m^2] + 4256979247.793130*z/1[m] - 691537634.412929)*1[K] when I evaluate the expression using 0.91 for z, the CFX gives me wrong number 1536K, while Excel is 762K. How do I change the decimal setup/precision in CFX? Thanks. Nan |
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November 30, 2013, 05:40 |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144 |
When you start the solver select double precision. But I vaguely recall that CEL is evaluated in single precision even with the rest of the numerics being double precision. I am not certain of this, but keep it is mind.
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November 30, 2013, 09:29 |
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#3 |
New Member
Join Date: Jun 2011
Posts: 5
Rep Power: 15 |
Hi, Glenn,
Thanks. I do have double precision turned on for solver. |
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December 13, 2013, 05:39 |
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#4 |
Senior Member
Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
Posts: 449
Rep Power: 20 |
maybe you can use the "function"-function from cfx pre to overcome the rounding errors if the expression is supposed to be used in the simulation.
Be very careful about the resolution of the points being used in the function, because they will be interpolated piece-wise between two points. You can also import data (like *.csv) for comparison in post - directly within the graph-tool. |
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