On the kinematics of scalar iso-surfaces in decaying homogeneous, isotropic turbulence

ABSTRACT

Scalar iso-surfaces have been used to describe many interface problems in turbulence, such as flame surfaces in turbulent reacting flows and turbulent/non-turbulent interfaces. In this paper we report on direct numerical simulations of the behaviour of iso-surfaces of two differently initialised conserved scalars evolving in isotropic turbulence. The terms in the equation for the iso-surface area density, along with the area density itself, are evaluated for a wide range of iso-surface values using a novel numerical method for evaluating surface integrals. Specifically, we quantify the behaviour of the iso-surface area density production term, related to the strain-rate, and the destruction term, related to iso-surface curvature and molecular diffusion. We find that production of iso-surface area density is not affected by the initial conditions, but it does have a small dependence on the iso-surface value. The destruction term depends not only on the iso-surface value, but also on the initial conditions.

KEYWORDS:

• Isotropic turbulence
• direct numerical simulation
• turbulent combustion

Acknowledgments

We gratefully acknowledge the AWS Cloud Credits for Research Program for providing the necessary resources to perform our simulations, as well as the support of NVIDIA Corporation with the donation of the Titan Xp GPU used for this research. This work was facilitated with support from PACCAR. The authors would like to thank Duane Storti for his assistance and insight into the surface integration methods used in this work, as well as Brad Perfect for his helpful conversations.

Disclosure statement

No potential conflict of interest was reported by the authors.