Gravity

[Anonymous]

Hello All,

I have been looking at ways to reduce "minor" head losses in pipes/ducts but before I can accurately model my concepts I have to learn to model losses from current ways of turning flows in pipes and ducts as well as assure I can correlate those models to published pressure losses.   My first model was of a long radius (r/d = 2.5) turn with a ten diameter straight section leading to the ninety degree turn and a thirty diameter section down stream of the turn.  A control model of straight duct with a length equal to the path of the forgoing was made.  The pressure was less for the ninety degree turn than for the straight pipe.  I felt that gravity may be at play here perhaps.  So I mades a second model of the straight pipe at a 45 degree angle with Z.  Both ends of the pipe were set at zero pressure gauge and the analysis did not run.  Gravity should move the fluid since it is sloped.  I then turned on the heat transfer model and specified -1 in the z direction and flow occured when both ends were set to zero gauge pressure.  For a dense fluid like water gravity can lead to "minor" losses that can not be ignored.  This begs the following questions:

1.  Do the standared parameters include the effect of gravity? 

2.  Must I always invoke heat transfer and specifiy gravity for it to be added to the model?

3.  If 2. above is true will the non fatal error message be a normal sign of a proper model?

4.  Does my model have the effects of gravity twice since I invoked it in the thermal part of the physics?  The results are diffent!

5.  Has any one done sensitivity studies to aerodynmaic analysis of flow over wings at reasonable reynolds numbers of around a million plus to determine the effect of not having gravity?

Finally, I could not easily find the answers to the above questions in the formums or Learning sections of the Autodesk Webb site.  I hope these are non trival questions from a newbie.  I look forward to your comments and feed back.

Have a blessed Weekend

Mike

P.S. I tried to attach the .cfz files but got: The contents of the attachement doesn't match file type. warning

[Anonymous]

Here are the .cfz files.  Explorer would not load them.  Had to switch to FireFox.....