web of flames – PDF

Study of flames in a Hele Shaw cell (between two glass plates with a gap of one centimeter) allows very precise experimental measurements . Quasi 2D premixed flames are obtained and studied with a simple image analysis. Results are compared to theoretical and numerical studies of the Sivashinsky equation, the non linear equation describing the non linear dynamics of premixed flames.

Quantitative results have been obtained for flames propagating in a Hele Shaw cells, using some simple image analysis. Growth rates of the linear Darrieus Landau instability have been measured, and the non linear evolution of the front can be predicted by the theoretical model .for short times.
We also study statistical properties of the flame, such as probability density functions of the cell sizes or the fractal dimension of the front
On the theoretical side, we show that it is possible to obtain analytical solutions of the Sivashinsky equation submitted to a shear flow..

A quantitative comparison of the Sivashinsky equation, the theoretical model of the non linear dynamics of premixed flames, to experimental quasi 2D flames, is performed in this project.
The study will be extended to very unstable flames submitted to an incident turbulence.

G. Joulin, B. Denet, Shapes and speeds of steady
forced premixed flames, Phys Rev E (2014) , 89,
063001

Almarcha C., Quinard J., Denet B., Al-Sarraf E., Laugier
J.M., Villermaux E., Cellular two-dimensional flames,
American Physical Society 67th annual DFD meeting,
San Francisco 23-25 Nov 2014, Gallery of Fluid motion
award (poster).

C Almarcha, J. Quinard, B. Denet,E. Al Sarraf, J.M.
Laugier, E. Villermaux, Experimental two dimensional
cellular flames, Physics of Fluids (2015), 27(9), 091110

Al-Sarraf E., Almarcha C., Quinard J., Denet B., Flame
speeds in a Hele Shaw cell, LBV2015 (laminar burning
velocity), Rouen, 23-24 march 2015.

This project aims at comparing nonlinear evolution equations for premixed flames in large scale burners , where hydrodynamic effects are important, called self turbulent flames, to experiments. This type of flames is expected to have more applications in the next few years, as they have a number of advantages in terms of pollution reduction. However these flames are poorly understood.

Building on recently developed experiments at the IRPHE laboratory that make use of a new device to damp acoustics and confirm the possibility of observing the propagation of wide flames through quiescent gases, we propose to experimentally study flames in simple situations such as a Hele-Shaw burner and test the predictions of theoretical models. The theoretical aspects will be developed in collaboration with G. Joulin (Pprime Institute), whose analytical works are a reference in the field. A better understanding of the coupling between turbulence and hydrodynamic instability of premixed flames is expected from this proposal.

The study of flames in the Hele-Shaw burner will allow very precise experiments, leading to quasi two dimensional flames, which will be easy to study by image analysis. The results will be compared to theoretical and numerical studies of the Sivashinsky equation, the well-known model equation describing the non linear dynamics of premixed flames.
We will study the statistical properties of flames in Hele Shaw cells, such as the probability density function of cells lengths or the fractal properties of the front. Analytical studies of the Sivashinsky equation will be performed, first in the case of a flame submitted to a stationary shear flow (where analytical solutions do not exist at the moment), then in the non stationary case. The study will be extended to very unstable flames submitted to an incident turbulence, with predictions of the turbulent flame velocity versus turbulence intensity. These predictions will be compared to experiments.