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Evolution of lean hydrogen-air premixed flames under high-frequency acoustic forcing: Flame morphology and displacement speed

Lookup NU author(s): Dr Xinyi Chen, Freddie Young, Dr Umair AhmedORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

Fully compressible numerical simulations of two-dimensional laminar lean hydrogen-air premixed flames have been performed, with the flame front subjected to acoustic forcing through the specification of a monopole-type sound source at the inflow. Simulations have been performed for acoustic frequencies ranging from 35 kHz to 500 kHz at two equivalence ratios, and . During the flame-acoustic interaction, the flame evolves from an initially weakly stretched state to exponential perturbation growth, wrinkle interaction, and the formation of non-linear cellular structures, with distinct linear and non-linear stages identified from Fourier mode analysis. The instability dynamics depend strongly on both forcing frequency and equivalence ratio. In the case of , the flame behaviour is strongly influenced by thermodiffusive instability, with a characteristic sequence of uniform cells, cell splitting, and cell merging. For , weaker thermodiffusive effects result in a response more strongly governed by hydrodynamic instability and large-scale wrinkle growth. At low forcing frequencies, flame corrugations remain relatively uniform, whereas at high frequencies the flame front becomes increasingly modulated and develops envelope-like structures, which can be interpreted as the interaction between an intrinsic standing cellular mode and the imposed acoustic disturbance. In the linear growth regime, the density-weighted displacement speed, , shows a linear correlation with total stretch rate, , for all forcing frequencies. While in the non-linear growth regime, two distinct branches appear, corresponding to weakly stretched flame segments and strongly negatively curved segments associated with flame pinch-off.

Publication metadata

Author(s): Chen X, Young FW, Ahmed U, Cant RS

Publication type: Article

Publication status: Published

Journal: Proceedings of the Combustion Institute

Year: 2026

Volume: 42

Pages: 106011

Online publication date: 01/07/2026

Acceptance date: 05/06/2026

Date deposited: 02/07/2026

ISSN (print): 1540-7489

ISSN (electronic): 1873-2704

Publisher: Elsevier Inc.

URL: https://doi.org/10.1016/j.proci.2026.106011

DOI: 10.1016/j.proci.2026.106011

Data Access Statement: Supplementary data provided in a PDF file linked in article

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