CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

How to apply velocity profile at inlet

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   November 6, 2004, 05:18
Default How to apply velocity profile at inlet
  #1
Sam
Guest
 
Posts: n/a
Hi everyone,

I have done some measurement for velocity profile at the diffuser inlet and I would like to put the experimental data as the inlet boundary condition. Can you please advise me of how to do it quickly? I found similar example in the tutorial but it used the 1/7 power law formula rather than the experimental data. Can I input the values rather than the formula for the inlet velocity profile?

Thanks a lot, Sam.
  Reply With Quote

Old   November 7, 2004, 01:05
Default Re: How to apply velocity profile at inlet
  #2
Neale
Guest
 
Posts: n/a
Yes, create a profile boundary condition file and use that. The file format is pretty easy to create, it's a CSV file with a header.

Neale
  Reply With Quote

Old   November 8, 2004, 02:17
Default Re: How to apply velocity profile at inlet
  #3
Sam
Guest
 
Posts: n/a
Hi Neale,

Thanks for your answer. Is there any example in the user manual? Shall be obliged if you can give me some quick references. I look at the Master Index but can't find the term CSV in there. Can I insert this file directly to the Pre? I'm using 5.7 now.

Thank you, Sam.
  Reply With Quote

Old   November 9, 2004, 00:21
Default Re: How to apply velocity profile at inlet
  #4
Neale
Guest
 
Posts: n/a
Look in Solver Modelling -> Boundary Conditions -> Profile Boundary Conditions, I think. If not there should be a link to it in the CFX-Pre documentation.

You can load a CSV file for 2D and 3D profiles. If your data is just a 1D profile setup a 1D CEL interpolation function and just type in the data or load it from a file.

Neale.
  Reply With Quote

Old   November 9, 2004, 03:22
Default Re: How to apply velocity profile at inlet
  #5
Sam
Guest
 
Posts: n/a
Hi Neale,

Thanks for your help. I'm almost there. Just one more question please.

I now specify the inlet axial velocity at the circular inlet cross section. Tangential & radial components are zero. Will that be okay if I only put two columns of data in the CSV file? ie. r[m] velocity w [ms^-1]

I don't need to include the theta in this case right?

Thanks again for your help.

Sam.
  Reply With Quote

Old   November 9, 2004, 03:43
Default Re: How to apply velocity profile at inlet
  #6
Sam
Guest
 
Posts: n/a
Hi Neale,

May be I should be a bit more specified about my question here.

I assume the velocity profile will only vary with r at the moment. The two column CSV file should work right? Will CFX apply the same velocity at different theta automatically if I don't write any theta value in CSV file (I have this doubt because inlet cross section is 2D rather than 1D)?

This is the data structure that I'm going to use here: [Data] r [ m ], Velocity w [ m s^-1 ]

Once I have the velocity data with different angle, I will include theta in my CSV file. May I know what's the unit of theta in CFX5.7?

Thanks a lot for your advice. Cheers,Sam
  Reply With Quote

Old   November 9, 2004, 18:40
Default Re: How to apply velocity profile at inlet
  #7
KKA
Guest
 
Posts: n/a
hey Sam the simple way is just ask CFX5.7 to write out a profile file at the section you want, and just used it to create your profile file. let say, you want to put it at a region called "inlet",

1. click file, export and under the type option select BC profile instead of generic or what have you.

2.select the parameters you want to appear inside your profile file.

3.then click okay.

Open the profilefile.csv to the format and the unit. You can then create the profile file .csv from your data using profilefile.csv as your template!!

regards
  Reply With Quote

Old   November 10, 2004, 08:55
Default Re: How to apply velocity profile at inlet
  #8
R P
Guest
 
Posts: n/a
You can use 1-D linear interpolation as you were trying, with extended minima and maxima. Two values of r and v(axial) should suffice.

R P
  Reply With Quote

Old   November 13, 2004, 01:12
Default Can we import data in cyclindrical cord?
  #9
Sam
Guest
 
Posts: n/a
Hi all,

Thank you for your help. I can now import the profile data in cartesian coord. I have one more question about the profile bc:

If I have organised the data in 2D cyclindrical coord (i.e. r & theta(deg)). Is there any straight forward way to tell CFX about the angle? I use "theta []" as the variable name but CFX seems not able to recognise this variable. Is that because I didn't plut the unit for theta? How can CFX know the column "theta" is one of the coord for 2D velocity contour?

Please kindly give me some clue. Thank you, Sam.
  Reply With Quote

Old   November 19, 2004, 12:58
Default Re: Can we import data in cyclindrical cord?
  #10
Ian
Guest
 
Posts: n/a
Should be possible, but you might need to set the domain up to be rotating. If it's not rotating but you just need access to cylindrical co-ords then omega = 0 is valid.
  Reply With Quote

Old   November 19, 2004, 14:08
Default Re: Can we import data in cyclindrical cord?
  #11
Ian
Guest
 
Posts: n/a
Sorry, just checked and you don't need to create a rotating domain. Cylindrical velocity components are available as an inlet BC in a non-rotating case.
  Reply With Quote

Old   March 31, 2012, 23:46
Default
  #12
Member
 
Hesam Moghaddam
Join Date: Mar 2012
Posts: 49
Rep Power: 4
hesamking is on a distinguished road
Hi,
My velocity profile changes with both time and r (=sqrt(x^2+y^2))
in other words, my inlet velocity is a function of r and t , u(r,t)
how can i define this profile that has two variables in CFX?
U = u(t) * (1-r^2)
thank you for your help.
Regards,
Hesam
hesamking is offline   Reply With Quote

Old   April 1, 2012, 06:52
Default
  #13
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,127
Rep Power: 79
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
This function should work fine as a CEL expression. Yes, an expression can have more than one input variable.
ghorrocks is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
3D UDF Paraboilc Velocity Profile (Can't Maintain) Sing FLUENT 9 November 26, 2014 08:58
Inlet Velocity in CFX aeroman CFX 12 August 6, 2009 18:42
non uniform velocity profile at inlet hiba FLUENT 2 July 25, 2006 03:32
Inlet velocity profile strudl CFX 0 July 18, 2003 09:58
what the result is negatif pressure at inlet chong chee nan FLUENT 0 December 29, 2001 06:13


All times are GMT -4. The time now is 07:59.