Understanding inner loops

chriss85 · March 18, 2014, 03:08

Hello,

I have a question that has been bugging me for a while now:

In schemes that use inner loops (like PIMPLE), or generally when calling eqn.solve() multiple times, how exactly are the fields updated? The way I understand it, is that the fields contain the new values after solving.

But here comes my question: Lets say I have an energy equation with a source term, why isn't the source term added multiple times to the energy when the equation is solved more than once? Does it store the old field somewhere and reference that in the iterative process of determining the new solution? The same goes for flow related problems, why doesn't the flow advance when the equation is solved multiple times?

My understanding of the inner workings of the solvers is unfortunately not deep enough so this doesn't appear obvious to me.

chriss85 · March 18, 2014, 03:53

Oh and one more thing, what's the difference between writing a term on the LHS or RHS of an equation? Is there any relevance to numerical precision or any advice that can be followed?

March 18, 2014, 03:08	Understanding inner loops	#1
chriss85 Senior Member Join Date: Oct 2013 Posts: 397 Rep Power: 19	Hello, I have a question that has been bugging me for a while now: In schemes that use inner loops (like PIMPLE), or generally when calling eqn.solve() multiple times, how exactly are the fields updated? The way I understand it, is that the fields contain the new values after solving. But here comes my question: Lets say I have an energy equation with a source term, why isn't the source term added multiple times to the energy when the equation is solved more than once? Does it store the old field somewhere and reference that in the iterative process of determining the new solution? The same goes for flow related problems, why doesn't the flow advance when the equation is solved multiple times? My understanding of the inner workings of the solvers is unfortunately not deep enough so this doesn't appear obvious to me.

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March 18, 2014, 03:53		#2
chriss85 Senior Member Join Date: Oct 2013 Posts: 397 Rep Power: 19	Oh and one more thing, what's the difference between writing a term on the LHS or RHS of an equation? Is there any relevance to numerical precision or any advice that can be followed?