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time dependant inlet velocity

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Old   March 24, 2009, 06:17
Default time dependant inlet velocity
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Hi everybody,
can anyone tell me how I can read the Excel file ( velocity-time) in cfx-pre as a inlet velocity. I don't want to find the trendline and use it as a expression I just need to use the excat data file.

Any help will be appreciated
Thanks
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Old   March 24, 2009, 08:52
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Quote:
Originally Posted by az_f View Post
Hi everybody,
can anyone tell me how I can read the Excel file ( velocity-time) in cfx-pre as a inlet velocity. I don't want to find the trendline and use it as a expression I just need to use the excat data file.

Any help will be appreciated
Thanks
Seems impossible. you may have to use step fuction or an equation as input
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Old   March 24, 2009, 10:05
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What about using a 1D User Function?
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Old   March 24, 2009, 10:17
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You can use a csv file as a profile data to patch the inlet, i.e. specify the boundary profile as you want. Please refer to Profile Boundary Conditions in help documentation.
Good luck.

Last edited by rikio; March 24, 2009 at 20:31.
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Old   March 24, 2009, 12:00
Default Use 1-D interpolation function
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You can create a user function and load a 1D table for your values.

In Excel:
Set up two columns in excel without headings, putting time in the first colum (the coordinate) and velocity in the second column (the value). Export this table to a comma delimetered file (.csv).

In CFX-Pre:
Create a new user function of type 1D interpolation. Right click in the coordinate/value panel and choose to import your data. Make sure you assign the proper units to the coordinate and value.

To use your function, just write the name and put 't' in brackets to pass it time. For instance, if you called it "my velocity profile" you would enter for velocity in your boundary condition "my velocity profile(t)".

Note that you can use this in an expression and pass any expression as the coordinate (as long as it resolves to the right units). For instance, you can increase the velocity by 10% and shift it back .25 seconds by doing the following:

my velocity profile(t-0.25 [s]) * 1.10

-CycLone
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Old   March 24, 2009, 22:50
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Thanks Cyclone, It works very well. Your advice is very helpful.

Best Regards,
Az
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