Reaction analogy based forcing for incompressible scalar turbulence

Journal Article · 05 September 2018 · Physical Review Fluids

DOI: https://doi.org/10.1103/PhysRevFluids.3.094602 · OSTI ID:1477698

Daniel, Don ^[1]; Livescu, Daniel ^[1]; Ryu, Jaiyoung ^[2]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Chung-Ang Univ., Seoul (Korea, Republic of). School of Mechanical Engineering

Here, we present a novel reaction analogy (RA) based forcing method for generating statistically stationary scalar fields in incompressible turbulence. The new method can produce more general scalar probability density functions (PDFs), for example, quasi-double- $\delta$ PDF, than current methods, while ensuring that scalar fields remain bounded, unlike existent forcing methodologies that can potentially violate naturally existing bounds. Such features are useful for generating initial fields in nonpremixed combustion, inlet conditions for spatially developing flows, or for studying non-Gaussian scalar turbulence. The RA method mathematically models hypothetical chemical reactions that convert reactants in a mixed state back into its pure unmixed components. Various types of chemical reactions are formulated and the corresponding mathematical expressions derived such that the reaction term is smooth in scalar space and is consistent with mass conservation. For large values of the scalar forcing rate, the method produces statistically stationary quasi-double- $\delta$ scalar PDFs. Quasiuniform, Gaussian, and stretched exponential scalar statistics are recovered for smaller values of the scalar forcing rate. The shape of the scalar PDF can be further controlled by changing the stoichiometric coefficients of the reaction. Finally, the ability of the new method to produce fully developed passive scalar fields with quasi-Gaussian PDFs is also investigated, by exploring the convergence of the scalar variance spectrum to the Obukhov-Corrsin scaling and of the third-order mixed structure function to the “four-thirds” Yaglom's law.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1477698
• Report Number(s): LA-UR--18-22664
• Journal Information: Physical Review Fluids, Journal Name: Physical Review Fluids Journal Issue: 9 Vol. 3; ISSN 2469-990X
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English