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how to simulate orifice in supersonic flow?

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Old   May 16, 2013, 05:30
Question how to simulate orifice in supersonic flow?
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liu zhiying
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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.

If somebody have other idea or suggestion on simulating orifice in supersonic flow., please help me.

Thanks in advance to all community for support.

Best regards.
Attached Images
File Type: png streamline1.png (6.1 KB, 27 views)
File Type: png velocity contours.png (6.3 KB, 25 views)
File Type: png streamline2.png (16.2 KB, 26 views)
File Type: png velocity contours2.png (6.3 KB, 26 views)
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Old   May 16, 2013, 09:58
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OJ
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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
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Old   May 16, 2013, 10:41
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liu zhiying
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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?
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