# fvm for unsteady term

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 July 5, 2020, 02:10 fvm for unsteady term #1 New Member   Jagan Mohan Join Date: Dec 2019 Location: New York Posts: 19 Rep Power: 4 Hello Friends, Greetings. I hope, you all are doing well. I'm trying to build an application in OpenFOAM. I'm starting from scratch as I think this is best way to learn what exactly happens behind screen. With all others details implemented into main function, compilation successful, lets focus on following. for (int i = 0; i <= 10; i++) { solve ( fvm::laplacian(kTh, T) ); runTime++; runTime.write( ); } As you can see, I'm solving steady Laplace conduction equation with no source terms. ControlDict settings are timeStep is 1 (these are now steady iterations) with some startTime and endTime. 1. What I observe is in first step itself, final residual goes to e-6 and it says iterations 46. What are these iterations and where are they coming from? 2. In all subsequent steps, residual does not change at all and so called iterations are zero. 3. When we write Laplacian solver in Matlab using FV Method, we see a residual plot which decreases. Why are we not seeing such thing in OpenFOAM? 4. Also, when solver knows that residual is less than tolerance value, why does not it stop iterating? (Like we see in Matlab code). Thank you, Jagan Mohan.

 Tags fvm::ddt(), fvm::laplacian

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