AnsweredAssumed Answered

Is my flow simulation setup correctly?

Question asked by Scott Rosoff on Aug 3, 2015
Latest reply on Aug 10, 2015 by Amit Katz

Hello,

 

I'm trying to find the head loss/pressure drop across an open channel for a specified flow rate. The picture below shows how the system looks.

 

ex1.jpg

Basically water flows through the left face, and has to go around a bunch of these glass rods, and exits out the other face.

 

Setup

  • Left face is an inlet with specified volumetric flow rate
  • Right face is specified to be environmental pressure
  • Surface goals are set up to be the average static pressure at inlet, and average static pressure at outlet
  • The rods are glass, so I set up a wall condition on them to have a roughness of 5 microinches (found this number online)
  • The base and "roof" of the system are steel, so they have a roughness of 200 microinches

 

ex2.jpg

 

Problem

I then run an internal analysis, and find that the pressure difference/head loss between the inlet and outlet is about .82 psi, which is way too high (it should be around .20 psi). This number doesn't change much if I change the roughness of the glass rods. However, if I specify 0 roughness for the glass rods, the head loss is around .20 psi, which is strange.

 

 

So, my questions are: Am I doing something wrong in my setup here? How can I diagnose this issue of having too high of a number? Is it possible that the glass rods aren't even recognized, and water's flowing straight through them?

 

Thanks,

Scott

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