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Numerics in OpenFoam - PBiCG vs. PCG

Posted August 18, 2016 at 14:13 by kindle
Updated October 12, 2016 at 11:27 by kindle

So the numerical scheme (fvScheme) will affect the property of the matrix to invert and we should choose properly the solver/solving algorithm (fvSolution) in order to solve it properly. Depending on the form of matrix depended on structured or unstructured mesh something like that.

Originally Posted by thg View Post
Hi Frog,

Meindert already mentioned, the difference between a PCG or a PBiCG,...
you can find in any textbook about linear iterative solvers like
Wessling, Saad, Trefethen, Stran,....
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Compile the solver laplacianFoam

Posted August 17, 2016 at 10:22 by kindle

laplcacianFoam is an implemented solver in OpenFOAM, which can be found in WM_PROJECT_DIR/platforms/.../bin (executable), .../application/solver/basic (dep) and WM_PROJECT_DIR/application/solver/basic (src).

Tried to compile from $FOAM_RUN, using laplacianFoam1. After comparing with authentic one, success.
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Writing the last iteration for steady state simulations

Posted August 17, 2016 at 05:09 by Ramwi

Ok, I have a very bad memory and furthermore, I did not find the solution to the bellow described problem right away. So, I will use this place to store the solution for future use.

Note: The proposed approach might be overcomplicated. If it is so, please let me know what is the "proper way".

Problem description: You run a steady state simulation (e.g. simpleFOAM) and you control the endTime (number of iterations) via the residualControl. Thus, the number of iterations...
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Accessing internal field and mesh from within boundary condition

Posted August 6, 2016 at 07:00 by kaifu

very useful.
Originally Posted by mchurchf View Post
Thank you all for your help,

I was able to implement my boundary condition as well. I used the following code to access the internal velocity field and the mesh two layers of cells inward from the boundary:

//  Set up access to the internal velocity field and mesh
    const volVectorField& U =
    const fvMesh& mesh = patch().boundaryMesh().mesh();
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How to calculate the polynomial coefficients of any arbitrary polynomial to fit data

Posted August 1, 2016 at 08:06 by Tobi

Dear all,

if you are interested in the calculation of polynomial coefficients to fit some data, you can check the method of least squares on my homepage. Here I explained everything in detail and also gave an example how to build the matrix A and the solution vector b for the problem we are discussing there. The polynomial that I am using in the example is:

\ln(\mu) = A + B \ln(T) + C\ln(T)^2 + D \ln(T)^3

How to build the matrix A and the solution vector...
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