×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Problem applying Pressure drop in Flotran.

Problem applying Pressure drop in Flotran.

Problem applying Pressure drop in Flotran.

(OP)
Hi Everyone,

I am  working on a 2-d Heat transfer problem ,in which there is  flow over a flat plate of finite thickness  kept in reatangular computational domain .I need to vary the upper and lower boundaries of the computational domain for the flow over a flat plate keeping the pressure drop constant across the inlet(left boundary) and outlet(Right) boundaries for all cases and also apply a constant inlet velocity for all cases.

The only boundary condition at the outlet -gradient of velocity is zero.

How do I apply a constant pressure drop across the inlet and outlet and also giving a constant velocity at the inlet??Can anyone help me with this??

regards,

Tom

RE: Problem applying Pressure drop in Flotran.

Hi,
if I understood well, the conditions needed are as follows:
- P1-P2=k1, where P1 is pressure @ inlet and P2 is pressure @ outlet
- v1=k2
- dv2/dL=0
From my understanding, these conditions are redundant:
- if you specify v1, there is no need to specify P1 altogether (=the problem is not pressure-driven); P2 will serve as a reference (=in Flotran pressures are relative ones), then P1 will be an output quantity and so will be P1-P2. If you have v1 already calculated "by hand" for a given P1-P2, then you should model your domain exactly as you did for the hand-made calcs (=null-roughness? laminar or turbulent model? etc...): you will see that P1-P2 obtained by the CFD for the imposed v1 will match what you expect (within a small error);
- if you specify P1 and P2, it is not correct to specify v1: the problem is pressure-driven. v1 will be an output quantity, provided that your domain is bounded by some wall somewhere (wind also is a bounded problem, where the dimensions of the domain are extremely large!), otherwise it is not really "physical" that a pseudo-infinite domain has a "natural" pressure difference...

To summarize:
1- if your plate is enclosed in a region bounded by walls, you can drive your problem either by velocity or by pressure (remember: geometrical properties + velocity condition + pressure condition are NOT an independent triplet of conditions: if you choose two, the third is dependent; for obvious reasons, a CFD can not change geo to accomodate imposed velocity + pressure)
2- if your plate is in an "external" region (=surrounded by a pseudo-infinite environment), the only choice from my point of view is to drive the problem by velocity.

Regards

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources