Reactive Flow Simulations

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Computional fluid dynamics (CFD) is a well-established method with an ever growing user base.[1,15] Fields of applications are broad and reach from incompressible laminar flows to turbulence modelling. In our group we focus on reactive flow simulations on various chemical relevant subjects such as catalytical combustion (e.g. industrial ammonia oxidation[16]) or pore diffusion. The idea, like with any type of simulations, is to reach a higher understanding of the underlying process, which is then used for optimization.

Automotive catalysis

Computational Fluid Dynamics are also a valuable tool for modelling automotive catalysts . Convection and diffusion have to be calculated for the channels in the honeycomb-like substrates which is usually done for a single representative channel. Reaction and (effective) diffusion have to be solved in the so called washcoat which is the porous catalytic phase on – and even inside (filters) – the channel walls. The tool used to create the respective models is COMSOL Multiphysics® where you can choose so called physics (e.g. laminar flow) to tailor your model.

Simulation of a porous channel wall consisting of substrate (white), catalyst and pores. The concentration of the reactant is color coded.
Simulation of a porous channel wall consisting of substrate (white), catalyst and pores. The concentration of the reactant is color coded.

Industrial ammonia oxidation

In the research of the industrial ammonia oxidation, we investigate the versatile complexity of the process ranging from micro-kinetic surface chemistry up to industrial scale.

For building up a fundamental understanding of the process, we start at micro-scale combining detailed simulations with data from a geometrically simplified experimental reactor. Using the optimized heterogeneous chemistry together with state-of-the-art homogeneous mechanisms[5–9] we are aiming to unify simulation and experimental results.

Depending on the viewed system size, it becomes necessary to reduce the mechanisms and/or use surrogate models (see Scientific Machine Learning ). For reduction, we are using the computational singular perturbation[12] or intrinsic low-dimensional manifolds[13] methods.

This allows us to adapt our gained knowledge on to laboratory reactor scale, focusing on the locally resolved simulation of an ammonia burner chamber.


[1] “CFD simulation in chemical reaction engineering”,, 2022.

[2] W. Koch, M. C. Holthausen, A Chemist's Guide to Density Functional Theory, Wiley-VCH, Weinheim, 2015

[3] H. G. Weller, G. Tabor, H. Jasak, C. Fureby, Comput. Phys. 1998, 12, 620.

[4] M. Maestri, A. Cuoci, Chemical Engineering Science 2013, 96, 106.

[5] Y. Song, L. Marrodán, N. Vin, O. Herbinet, E. Assaf, C. Fittschen, A. Stagni, T. Faravelli, M. U. Alzueta, F. Battin-Leclerc, Proceedings of the Combustion Institute 2019, 37, 667.

[6] A. Stagni, C. Cavallotti, S. Arunthanayothin, Y. Song, O. Herbinet, F. Battin-Leclerc, T. Faravelli, React. Chem. Eng. 2020, 5, 696.

[7] K. P. Shrestha, L. Seidel, T. Zeuch, F. Mauss, Energy Fuels 2018, 32, 10202.

[8] P. Glarborg, J. A. Miller, B. Ruscic, S. J. Klippenstein, Progress in Energy and Combustion Science 2018, 67, 31.

[9] M. Kovács, M. Papp, I. G. Zsély, T. Turányi, Fuel 2020, 264, 116720.

[10] R. Li, A. A. KONNOV, G. He, F. Qin, D. Zhang, Fuel 2019, 257, 116059.

[11] A. Jess, P. Wasserscheid, Kapitel Ammonia Oxidation // Chemical technology. An integral textbook, Wiley-VCH, Weinheim, 2013.

[12] S. H. Lam, Combustion Science and Technology 1993, 89, 375.

[13] U. Maas, S. B. Pope, Combustion and Flame 1992, 88, 239.

[14] L. S. Avila, The VTK user's guide, 11. Aufl., Kitware, Columbia, 2010.

[15] R. Schwarze, CFD-Modellierung 2013, Springer-Verlag, 1st edition, 3-9

[16] Haas M, Nien T-W, Fadic A, Mmbaga JP, Klingenberger M, Born D, et al. N2O selectivity in industrial NH3 oxidation on Pt-gauze is determined by interaction of local flow and surface chemistry: A simulation study using mechanistic kinetics. ChemRxiv. Cambridge: Cambridge Open Engage; 2022; This content is a preprint and has not been peer-reviewed.