The Effect of Noise on the Propagating Speed of Pre-mixed Laminar Flame Fronts

TL;DR

This paper investigates how thermal noise influences the speed of premixed laminar flames, revealing that noise significantly reduces flame speed beyond predictions of noise-free models through detailed stochastic simulations.

Contribution

It introduces a comprehensive stochastic PDE model incorporating detailed chemical kinetics and develops numerical methods to accurately simulate noisy flame propagation.

Findings

Thermal noise causes significant reduction in flame speed.

Stochastic effects are amplified out of equilibrium, affecting macroscopic behavior.

First detailed simulation of noisy flames with full chemical kinetics.

Abstract

We study the effect of thermal noise on the propagation speed of a planar flame. We show that this out of equilibrium greatly amplifies the effect of thermal noise to yield macroscopic reductions in the flame speed over what is predicted by the noise-free model. Computations show that noise slows the flame significantly. The flame is modeled using Navier Stokes equations with appropriate diffusive transport terms and chemical kinetic mechanism of hydrogen/oxygen. Thermal noise is modeled within the continuum framework using a system of stochastic partial differential equations, with transport noise from fluctuating hydrodynamics and reaction noise from a poisson model. We use a full chemical kinetics model in order to get quantitatively meaningful results. We compute steady and dynamic flames using an operator split finite volume scheme. New characteristic boundary conditions avoid non-physical boundary layers at computational boundaries. New limiters prevent stochastic terms from introducing non-physical negative concentrations. This represents the first computation of a model with thermal noise is a system with this degree of physical detail.