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Old   February 7, 2006, 06:19
Default opening pressure for entrainment
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can somebody help me, please. I am simulating the flow in a booth system for powder coating. Something like a hugh box with several windows and other openings through which air is sucked in. For the boundary conditions of the surrounding space I set "Entrainment Condition" using cfx5.7. This works without a problem. But now I have to use cfx10 and there are two options: "opening pressure for entrainment" and "static pressure for entrainment". I have tried both, but in both cases it is the same. At the beginning of the calculations (eg. iteration 100) air comes from all directions into the domain. At the end (eg. iteration 300 rms 10^-5) the air comes only from one direction in a 45deg angle to the boundary. This is not realistic...


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Old   February 9, 2006, 07:21
Default Re: opening pressure for entrainment
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Hi Tilman,

For following your question.

I've just noticed the same thing actually, haven't looked up the cfx10 manual yet. I will list the options and see if anyone can highlight the purposes of this change (suprisingly, cfx10 also suggests you which option is better or more robust)

In cfx5.7.1 the options are:

Pressure and direction (stable) *** Pressure and no direction (entrainment) *** Static pressure

In cfx10 the options:

Opening Pres. and Dirn *** Opening Pres. (entrain) *** Static Pres. and Dirn *** Static Pres. (entrain)

I wondered how they are related? 3 of them just called different names? what about the new added option (don't know which one)?

Thanks a lot

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Old   February 9, 2006, 08:28
Default Re: opening pressure for entrainment
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The difference between these options have been explained in user manual. However, I found that they don't affect the solution much in my problem. New option may be useful when there is significant amount of reverse flow at outlet.
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Old   February 10, 2006, 05:09
Default Re: opening pressure for entrainment
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Hi, thanks for your reply. According to the cfx10 manual "opening pressure for entrainment" should be normally the best choice for my case. I have tried "static pressure and dim" and it leads to better results, but not as good as "Pressure and no direction (entrainment)" in cfx5.7.1.

It might be interesting how the "Pressure and no direction (entrainment)" option is called in cfx10?


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