# Urgent help needed in creating UDF's

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

October 11, 2013, 23:48
Urgent help needed in creating UDF's
#1
New Member

Sharath Chandra. J
Join Date: Sep 2013
Posts: 3
Rep Power: 6
I am currently working on validation of a small project and it includes flow conditions in parabolic profile and temperature conditions varying in a linear fashion increasing along the Y axis.

Velocity varies as
u(y)=12(y-(y^2)) and y ranges from -1/6 to 1/2

Temperature varies as
θ(y)=(1-2y) and again y ranges from-1/6 to 1/2

My main problem is i don't understand how to define the centre-line velocity i.e maximum velocity and temperature conditions. Also from a previous experience, I couldn't include two different UDF's for different boudary conditions. Is it possible to write both the UDF's in a single program

I have included all the required data probably. In case anything else is required, I would respond. Please help me out.
Attached Images
 help required.jpg (58.2 KB, 14 views)

October 12, 2013, 09:55
#2
Senior Member

Daniele
Join Date: Oct 2010
Location: Italy
Posts: 998
Rep Power: 17
Quote:
 Originally Posted by sharath chandra I am currently working on validation of a small project and it includes flow conditions in parabolic profile and temperature conditions varying in a linear fashion increasing along the Y axis. Velocity varies as u(y)=12(y-(y^2)) and y ranges from -1/6 to 1/2 Temperature varies as θ(y)=(1-2y) and again y ranges from-1/6 to 1/2 My main problem is i don't understand how to define the centre-line velocity i.e maximum velocity and temperature conditions. Also from a previous experience, I couldn't include two different UDF's for different boudary conditions. Is it possible to write both the UDF's in a single program I have included all the required data probably. In case anything else is required, I would respond. Please help me out.
Hi!
Please define your equations; if I plot the velocity equation between -1/6 and 1/2 I have negative velocities and the profile of the parabola is not complete.
If I translate the parabola and if I plot that translated parabola the profile of the parabola is not complete.

Do the same with the T equation.

Can you define better your problem?

Daniele
Attached Images
 chart.jpg (27.3 KB, 7 views)

October 12, 2013, 13:12
RE: Data clarification
#3
New Member

Sharath Chandra. J
Join Date: Sep 2013
Posts: 3
Rep Power: 6
Quote:
 Originally Posted by ghost82 Hi! Please define your equations; if I plot the velocity equation between -1/6 and 1/2 I have negative velocities and the profile of the parabola is not complete. If I translate the parabola and if I plot that translated parabola the profile of the parabola is not complete. Do the same with the T equation. Can you define better your problem? Daniele
Hi! First let me thank you for such an immediate response. I am really grateful to you for your help. Anyways back to the problem at hand.

The problem I am working on is a backward facing step flow with varying expansion ratios. I have to validate the flow conditions in the problem for varying ratios of S/H as shown form the figure. From the paper I've been trying to validate this sentence is verbatim.
" The physical domain in the X-direction is bounded by 0 < x < (30H) and in the y direction it is bounded by –S/DH < y < 1/2.
The flow at the inlet, x=0 is assumed to be hydro-dynamically fully developed, where a dimensionless parabolic velocity distribution is given as
u(y)=12(y-y^2)."
If having the Reynolds number of the flow would be helpful, then it is 800 and the fluid is assumed as water with standard properties.

 Tags temperature bc, udf, velocity bc

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Ardalan Main CFD Forum 2 March 18, 2011 16:22 Boris Kloser FLUENT 2 December 12, 2009 04:16 mike FLUENT 7 November 7, 2008 07:11 nick Siemens 14 June 29, 2008 18:48 Ken Adams FLUENT 3 September 25, 2007 23:50

All times are GMT -4. The time now is 00:44.