Scrutinizing proposed extensions to the Eddy Dissipation Concept (EDC) at low turbulence Reynolds numbers and low Damköhler numbers
Peer reviewed, Journal article
Published version
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https://hdl.handle.net/11250/2788700Utgivelsesdato
2022Metadata
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Sammendrag
Recent proposals to modify or extend the Eddy Dissipation Concept are investigated and compared to the standard EDC. The results with respect to the underlying principles of EDC are examined. A total of four different variants of the extended EDC are available, expressing locally determined values for two model coefficients that are constants in the standard EDC. The effects on the fine-structure region mass fraction and the fine structure time scale are demonstrated with resulting effects on the mixing and species mean reaction rate. It is found that the constraints imposed on the locally determined coefficients are more important for the results than the formulated dependencies of turbulence Reynolds number and microscale Damköhler number. Furthermore, some of the versions require a less-than-unity limitation for the fine-structure mass fraction for wide ranges of the Reynolds number. All the modified model versions maintain the EDC cascade model, and their relations to this model are investigated. A finding is that some versions maintain very high viscous effects at high turbulence Reynolds numbers. Comparison with the standard EDC shows that some of the effects motivating the extensions are already present in the standard EDC. Initially, a short cascade for low turbulence Reynolds numbers is derived from the existing EDC cascade model, which was developed for high Reynolds numbers. The resulting changes are small, and the need for a modification still remains.