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Droplet-induced stretch effects on lean premixed hydrogen-air flame front

Maria Rosaria Acquaviva* and Ivan Langella

  • Faculty of Aerospace Engineering, Department of Fluid Physics and Technology, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands

  • *Contact author: M.R.Acquaviva@tudelft.nl
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Phys. Rev. Fluids 11, 073201 – Published 29 July, 2026

DOI: https://doi.org/10.1103/skq6-zhtm

Abstract

The interaction between a single water droplet and a lean premixed hydrogen-air flame is investigated using two-dimensional detailed-chemistry simulations in an Eulerian-Lagrangian framework. A single cusp flame configuration is employed to impose a controllable curvature to the flame and isolate the effects of droplet-induced stretch. When the water droplet evolves in an inertia-dominated regime, it acts as a localized momentum and heat sink, generating a transient deformation of the flame front and a reduction in the local displacement speed. It is observed that curvature gradient generated by the droplet-flame interaction, contributes to the decrease in flame speed and heat release rate by reducing the reactants focusing effect. This result is confirmed by comparison with an equivalent simulation performed under a unity Lewis number assumption, where curvature-induced differential diffusion effects are artificially suppressed. The analysis of droplet-induced stretch further shows that the interaction produces a local curvature inversion of approximately 40% of the initial flame shape, while the tangential strain rate component of stretch increases and counteracts this effect. After the interaction, the flame gradually recovers its original shape, and the curvature perturbation decays exponentially with a restoring time governed by the flame diffusion timescale. An analytical model using an analogy with a mass-spring-damper system is proposed to estimate the local flame displacement and displacement speed during the droplet-flame interaction.

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Phys. Rev. Fluids 11, 073201– Published 29 July, 2026
  • Received 26 January 2026
  • Accepted 8 July 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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