Saturday, December 21, 2013

Github Code

I just wanted to share and link some code that I had uploaded to Github a while ago:

Mainly there are two things:
      -OpenFOAM Code.
      -Incompressible flow solver, and related utilities.

The incompressible flow solver is based on J.B. Perot's Exact Fractional Step Method. I wanted to use this instead of OpenFOAM's PISO for transient flows. Theoretically and practically in my opinion the Exact Fractional Step Method is superior; you can find more information from Perot directly with a simple Google search. From scratch, I coded it in C (with the awesome tool VALGRIND) and got to the point of being able to simulate a 2D box in a wind tunnel using an unstructured-multiblock grid. However, the additional features I required (3D, sliding mesh interface) proved too much in terms of time and effort (especially debugging!), so I reverted back to OpenFOAM.

The OpenFOAM modules are very useful and I use them heavily today. They include mesh motion functions for the AMI moving region and turbulence models. Take a look at them if you are interested.
     -Nested rotating interfaces: regions rotating and translating inside of another rotating region, i.e. cyclorotor simulations.
     -Ramped rotating motion: linear speedup of rotational velocity, to allow for Courant numbers not affected too much by high-velocity transients. This is supposed to allow for faster resolution of low-frequency starting phenomenon in transient simulations.
     -Proper and Official Spalart-Allmaras Turbulence Model: From a research publication written by Spalart himself in 2013. He acknowledges the confusion and variation of in the popular RANS model and establishes the correct and most up-to-date way to implement it. It differs quite a bit from the OpenFOAM standard S-A model.
     -Spalart-Allmaras with ROTATION/CURVATURE CORRECTION: Detailed in Zhang and Yang (2013), this model utilizes the Richardson number to sensitize the S-A to rotation and curvature (R/C), while bypassing the significant additional computation required by standard S-A R/C correction models. The more efficient model is shown in the paper to provide almost identical results to the traditional model in several test cases.
     -And others... take a look!

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