DNS analysis of turbulent mixing in two-phase flows

Abstract

This study focuses on the evaporation and mixing process in turbulent two-phase flows with a direct resolution of the flow near the interface. A first approach, using a passive scalar to represent the evaporation and mixing process in a two-phase dense turbulent flow, has been developed and applied in a homogeneous isotropic turbulence over a large range of liquid volume fractions. This model is restricted to low vaporization rates, thus the interface is barely affected by the evaporation process. A statistical analysis of the vapor field is performed. Obtained results suggest that the beta PDF, frequently used in combustion modeling, are not adequate to represent the state of scalar mixing when interfaces are taken into account. A spectral analysis of the velocity and the scalar field is carried out simultaneously in both phases as well as in each phase separately. A procedure using the liquid volume fraction field is employed to separate the contribution of each phase. The evaporation process does not affect the spectrum shape of the scalar, but it has a direct influence on the energy level of the scalar.

Volume of Fluid (VOF) type advection methods in two-phase flow: A comparative study

“…The Archer 3D code, developed at CORIA-INSA institute, is a MAC-type (staggered grid) Navier-Stokes solver. Up to now, it has been applied for example to model primary atomisation [21,6], as well as turbulence DNS analysis [12]. The MGCG (Multigrid with Conjugate Gradients) [8,14] methods are used to solve Poisson equation.…”

Potential of Two-Phase Flows DNS to Characterize Interactions between Turbulence and Widely Deformed Interface

“…The solution is carried out in a 3D cubical domain with periodics boundaries similar to the study of [19] and [8].…”

“…The periodic box initialization is based on the work of [19,8]. Eight droplets are introduced in each corner of the domain, the sum of their volume is equal to the fixed liquid volume fraction equal to 5% in our case.…”

“…In single-phase flows, DNS of Homogeneous Isotropic Turbulence (HIT) is still used to study scalar mixing and the Kolmogorov theory. Extension of this configuration to two-phase flows to characterize interface/turbulence interactions is emerging in recent DNS studies: with a freely decaying turbulent two-phase flow ( [32]), with a forced HIT ( [18], [19], [8]), with solid particles in an HIT ( [6]), and with a downward turbulent flows for bubbly flows ( [17]). …”

“…We purpose in this study to investigate such interaction between liquid/gas interface and turbulent flow in a forced HIT with a DNS. This configuration was used in [8] to the transport of a passive scalar. It is important to point out that our study considers high Reynolds and high Weber numbers, corresponding to the atomization regime.…”