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-   -   How does PIMPLE work? (http://www.cfd-online.com/Forums/main/91670-how-does-pimple-work.html)

derkermit August 18, 2011 12:37

How does PIMPLE work?
 
Hi,
I would be very glad, if someone could explain me the process behind PIMPLE. Up to now my knowledge about this is this:
  • PIMPLE is a hybrid of SIMPLE/PISO
  • It's pseudo-transient
I'm working with OpenFOAM and using the buoyantPimpleFoam-Solver which informs me at the beginning of the calculation, that it's running in PISO-Mode. I searched the sourcecode for the appropriate statement but don't understand what's the clue behind it.

So far, my questions:
  • Which properties of PISO/SIMPLE are merged into PIMPLE?
  • What exactly is the gain from using PIMPLE?
  • Does PIMPLE switch from PISO to SIMPLE at a specific point? Maybe during the transient period it's using pressure correction basend on PISO and when the flow gets steady it switches to SIMPLE. Does that make sense?
Really appreciating your answers ;)

Thank you very much,
Alex

leflix August 18, 2011 15:55

I don't know PIMPLE but what is sure is that the use of SIMPLE is not restricted only on the seek of steady solution.

derkermit August 21, 2011 13:05

Yes thats why I mentioned the switch to SIMPLE when the flow gets steady.
Does nobody use PIMPLE or why is there nearly nothing in books or on the net?

wyldckat August 21, 2011 15:00

Pimple=42?
 
Greetings to all!

@derkermit: Time for a summarized story:
Quote:

Originally Posted by http://en.wikipedia.org/wiki/The_Hitchhiker%27s_Guide_to_the_Galaxy#The_Hitchhi ker.27s_Guide_to_the_Galaxy
(...) a race of hyper-intelligent pan-dimensional beings who built a computer named Deep Thought to calculate the Answer to the Ultimate Question of Life, the Universe, and Everything. When the answer was revealed to be 42, Deep Thought explained that the answer was incomprehensible because the beings didn't know what they were asking.

Here's a more detailed plot summary. The moral of this summarized story: asking the right people with the right questions will get you at the very least a good answer ;)
In other words, you should have asked in one of these sub-forums:
Here's a quote from a post just today from there:
Quote:

Originally Posted by alberto (Post 320875)
PISO simply does not iterate over the equations: it solves alpha, Theta, U, p, k, epsilon and proceeds in time.

PIMPLE is a combination of PISO and SIMPLE. In other words you can have outer correctors, if you set the appropriate keyword in the fvSolution PIMPLE sub-dictionary.

Best regards,
Bruno

derkermit August 21, 2011 15:45

Thanks!
I thought that my topic isn't a openfoam-specific one... :o

wyldckat August 21, 2011 18:07

Quote:

Originally Posted by derkermit (Post 320912)
I thought that my topic isn't a openfoam-specific one... :o

Mmm... good point. Nonetheless, here you have two links for the SIMPLE and PISO algorithms: http://openfoamwiki.net/index.php/Ma...rGuideAddendum - but the PIMPLE is not explained yet. PIMPLE isn't even listed yet on openfoamwiki.net at all :(

OK, now I see why you deduced it would be a general topic... but still, it could also be interpreted as one of those things that isn't yet very well documented in OpenFOAM, and very specific to it ;)

Yuri Almeida February 20, 2013 16:34

Foamers,

Anyone found something documented (article, phd thesis, book...) explaining the PIMPLE?

Att,


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