Turbulent Combustion and Developments In OpenFOAM® - Markus Bösenhofer (K1MET/TUW), Christian Jordan (TUW), Michael Harasek (TUW)

Combustion modeling in OpenFOAM is still something of a lame duck in OpenFOAM. Considering the main forks, there are few possibilities for modeling the turbulence-chemistry interaction especially when detail chemistry is involved. One of them is the partially stirred reactor (PaSR) model integrated to the OpenFOAM Foundation release. Basically, the PaSR model corrects the laminar reaction rate determined by integrating a plug-flow reactor (PFR) for the given time step size. The correction factor is a function of the chemical time scale and the mixing time scale, which can be influenced by an empirical constant Cmix, and divides the volume cell in a reacting and non-reacting part.

However, the Eddy Dissipation Concept (EDC), which is very common in turbulent combustion and can be seen as “state-of-the-art”, is missing in all major OpenFOAM releases. The EDC uses a similar approach as the PaSR model: volume cells are divided into reacting fine structures and non-reacting surroundings. The reacting fraction of the volume cells is determined by assuming a turbulent energy cascade with a characteristic frequency. In addition, the fine structures are treated as a perfectly stirred reactor (PSR) and integrated to steady-state. Thus, the EDC model is computationally expensive and requires some kind of chemistry tabulation for engineering applications.

In this work, differences between these two concepts of turbulence-chemistry interaction are discussed. Furthermore, recent trends and developments in the OpenFOAM chemistry classes are presented.

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