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2D Venturimeter Analysis Problems

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Old   November 30, 2015, 17:06
Question 2D Venturimeter Analysis Problems
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Sean
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Hi guys,

I have a problem to model the flow of water through a ventuimeter using ANSYS WORKBENCH 14; FLUENT, however I am a bit of a beginner and am having some problems setting up my solutions.

I had set up the analysis as 2D, and modelled the top half of the geometry (the line of symmetry is set up as an axis in the set-up) and created a bias in the mesh towards the venturi throat.

In my set up I use the k-epsilon model as the flow is turbulent and have enhanced wall treatment enabled. The fluid is water and is defined as such, and enters the pipe at a velocity of 4.77 m/s as defined in ANSYS.

The inlet is set as a velocity inlet, centreline as an axis, wall as a wall and outlet as a pressure outlet.

However when I run my calculation the solution does not converge and I am continually faced with being told that the flow is reversed?

Any help at all on how to successfully setup my problem and obtain solutions would be kindly received.

Cheers
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Old   November 30, 2015, 18:45
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Hi!

Did you elongate the outlet to avoid backflow?
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Old   November 30, 2015, 19:30
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Hi!

Did you elongate the outlet to avoid backflow?
I just read an older post after I started this thread. Back in tomorrow afternoon so will try that and update. Thanks!
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Old   December 1, 2015, 01:48
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Perfect! Good luck and keep us updated!
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Old   December 1, 2015, 16:00
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Perfect! Good luck and keep us updated!
That sorted it I think, thanks for the help! Is there a reason why I was having that problem with a shorter length?
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Old   December 1, 2015, 16:49
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Yep. The flow probably detaches at the venturi's wall. This creates a backflow that difficults the convergence.

Since this is probably your case, you may want to check the k omega sst model, instead of the k epsilon ewt. In models with detached flow like venturis, it may underpredict the pressure losses. But i'm new also in this, so dont trust me much
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