PCG solver
 

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.

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).