Comparison of Flame Propagation Statistics Extracted from Direct Numerical Simulation Based on Simple and Detailed Chemistry—Part 1: Fundamental Flame Turbulence Interaction

Abstract

In the present study, flame propagation statistics from turbulent statistically planar premixed flames obtained from simple and detailed chemistry, three-dimensional Direct Numerical Simulations, were evaluated and compared to each other. To this end, a new database was established encompassing five different conditions on the turbulent premixed combustion regime diagram, using nearly identical numerical methods and the same initial and boundary conditions. A detailed discussion of the advantages and limitations of both approaches is provided, including the difference in carbon footprint for establishing the database. It is shown that displacement speed statistics and their interrelation with curvature and tangential strain rate are in very good qualitative and reasonably good quantitative agreement between simple and detailed chemistry Direct Numerical Simulations. Hence, it is concluded that simple chemistry simulations should retain their importance for future combustion research, and the environmental impact of high-performance computing methods should be carefully chosen in relation to the goals to be achieved.

Comparison of Flame Propagation Statistics Based on Direct Numerical Simulation of Simple and Detailed Chemistry. Part 2: Influence of Choice of Reaction Progress Variable

“…Moreover, displacement speed statistics are typically taken on a specific isosurface within the flame front, which again requires the definition of a reaction progress variable together with the identification of the isolevel of reaction progress variable. It has been shown in the first part of this work [23] that displacement speed statistics and their interrelation with curvature and tangential strain rate are in very good qualitative and reasonably good quantitative agreement between simple and detailed chemistry DNS. The present work goes into more detail by analysing the individual components of displacement speed as well as the surface density function (i.e., magnitude of the gradient of reaction progress variable) and their interdependencies with curvature and strain.…”

“…Two different compressible high order DNS codes SENGA [34] and SENGA2 [35] have been used for the present analysis which are described in detail in part 1 of this paper [23] together with all the necessary information related to this database. Both codes solve the conservation equations of mass, momentum, energy and species (see [34,35]) which can also be found in the textbook of Poinsot and Veynante [26].…”

“…Snapshots of the flame contours at the time when statistics are extracted are exemplarily shown for one case only in Figure 1b. For more details and all flame contours the reader is referred to the first part of the paper [23]. and ratio of specific heats (β = 6.0 , Pr = 0.7, γ = 1.4).…”

“…It becomes clear from the foregoing discussion that it is not straightforward to identify one, correct physical system representation for combustion DNS and it should be selfevident, that the methods chosen for the scientific analysis should be commensurate with the requirements of a specific scientific purpose, as argued in [23] because highperformance computing is itself responsible for non-negligible carbon emissions [24,25]. Another tradeoff that should be considered is that SC simulations allow for large parametric variations and at least in some respects, it might be possible to extract more physical insight from a larger matrix of simulations compared to a few very detailed DNS runs.…”

“…The same DNS database that was used in reference [23] has been used for this analysis. Although detailed discussions on this database and its numerical implementation were provided in [23], some of that information is repeated here for ensuring the self-contained nature of this paper in Section 2. This will be followed by a detailed discussion of the results and finally, conclusions will be drawn.…”