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 sharath chandra October 11, 2013 23:48

Urgent help needed in creating UDF's

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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.

 ghost82 October 12, 2013 09:55

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Quote:
 Originally Posted by sharath chandra (Post 456474) 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

 sharath chandra October 12, 2013 13:12

RE: Data clarification

Quote:
 Originally Posted by ghost82 (Post 456529) 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.

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