# how to simulate orifice in supersonic flow?

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May 16, 2013, 06:30
how to simulate orifice in supersonic flow?
#1
New Member

liu zhiying
Join Date: May 2013
Posts: 2
Rep Power: 0
Good afternon,

I have some problems in simulating orifice in supersonic flow.

As shown in the following picture is my model. The left side is entrance, and the right side is exit. The diameter of entrance and exit are 5mm. The diameter and thick of the orifice are 0.12mm and 0.2mm, respectively.

ideal gas, k-e viscous model

The inlet is set as pressure-inlet with total pressure of 1atm, and the outlet is as pressure-outlet with an gauge pressure of 600Pa.

if I use pressure based as solver, the results are shown in the following picture.
streamline

velocity contours

The mass flow rate of inlet and outlet are 2.1621258e-6kg/s and -2.1409824e-6kg/s, respectively.

if I use density based as solver, the results are shown in the following picture.
streamline

velocity contours

The mass flow rate of inlet and outlet are 1.9779529e-6kg/s and -2.0015871e-6kg/s, respectively.

The question is which solver should be selected to simulate the orifice in supersonic flow.
If I select pressure based as solver, the streamline in the picture looks good, while velocity contours looks not good. If I select density based as solver, the streamline in the picture looks not good, while velocity contours looks good.

Thanks in advance to all community for support.

Best regards.
Attached Images
 streamline1.png (6.1 KB, 45 views) velocity contours.png (6.3 KB, 39 views) streamline2.png (16.2 KB, 40 views) velocity contours2.png (6.3 KB, 41 views)

 May 16, 2013, 10:58 #2 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 473 Rep Power: 18 Hope you have done adequate mesh independence study. Try density based coupled solver here. Try with first order discretization and get a nice convergence and then switch to second order. Have you tried realizable model? It tends to model the jets better than k-eps. OJ

 May 16, 2013, 11:41 #3 New Member   liu zhiying Join Date: May 2013 Posts: 2 Rep Power: 0 dear OJ thanks for your answer. I set grid density 100 point per 1mm in both the axial and the radial direction through I have not done adequate mesh independence study. Because it is adequate according to a thesis. For realizable model, you mean maybe the diameter of entrance should be narrow and the length between orifice and exit should be extended?

 Tags fluent, orifice, supersonic flow