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PCG solver

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Old   December 27, 2016, 02:12
Post PCG solver
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parth chavan
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Dear all Foamers,

To simulate the nozzle flow with steady state condition, I am finding difficulties. I already have utilised more number of days than usually required to solve such problem. Finally I changed my solver from smooth to PCG with DIC conditioning and my problem ran for 500 iterations.

I simply changed my solver from smooth to PCG. I want to know what is Preconditioned Conjugate Gradient regarding CFD and where I can employ these solvers.(in short I would like to know the applications of solvers present in openFoam)

Any help will be much appreciated.

Thanks.
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Old   May 20, 2022, 11:04
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Uttam
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Conjugate gradient solvers are typically an accelerated gradient descent solver. It is used for solving the system of linear equations Ax = b which is encountered after discretisation of the domain and applying boundary conditions. The pre-conditioning is sort of a way to ensure faster convergence. Basically the pre-conditioner is useful for systems that have a large condition number (condition number is the ratio of the largest to the smallest eigenvalue of a system of equations). Having a large condition number means that the magnitude of the gradient in each step is small thereby requiring a lot of iterations to converge. Actually for a steady state problem, you can use the GAMG (geometric agglomerated algebraic multi grid solver).
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