Numerical convergence of volume of fluid based large eddy simulations of atomizing sprays

Abstract

This paper presents three volume of fluid (VoF)-based methods for large eddy simulations of atomizing sprays with different treatments of the unresolved interface. The turbulent filtered VoF model uses conventional turbulent viscosity models to close the combined interfacial and turbulent sub-grid fluctuations. The hybrid turbulence filtering and artificial compression model includes an additional artificial compression term that is applied along regions where the liquid–air interface is continuous, while conventional turbulence filtering is activated in regions with discrete liquid objects. The new explicit volume diffusion model (EVD) is based on the concept of averaging the VoF equations over explicitly defined physical volumes that are independent of the numerical grid. Closure models of the sub-volume flux and stress terms introduce explicit volume diffusion and explicit volume viscosity that are physically defined and linked to the volume size. Numerical convergence is achieved by reducing the grid size while keeping the explicit volume size constant. The models are tested for two experimental atomizing spray cases with different Weber numbers. The superior numerical convergence of the EVD model is demonstrated by analysis of the mean and rms of the volume fraction and velocity fields. Two models for the surface tension force are investigated for the EVD simulations. Compared with the simple surface tension model which neglects sub-grid fluctuations, an improved volume-averaged model based on fractal properties of wrinkled sub-volume interfaces gives better predictions of the mean volume fraction relative to the experimental data but requires selection of a model constant.

Edward E. O'Brien contributions to reactive-flow turbulence

“…These contributions are on diverse topics including combustion instability, 150,151 scalar mixing, [152][153][154][155][156] homogeneous isotropic turbulence, [157][158][159][160] turbulent premixed flames, [161][162][163][164][165][166][167][168][169][170][171] turbulent non-premixed flames, [172][173][174][175] wallbounded turbulence, [176][177][178] turbulent combustion modeling, [179][180][181] FDF/PDF, [182][183][184][185][186][187][188][189][190][191][192] and two-phase turbulent flows. [193][194][195][196][197][198]…”

Inhibitory Effects of Convergent Annular Nozzles on the Primary Breakup of Discontinuous Shear-Thickening Suspensions

“…The mechanisms of the primary breakup have gained lots of interest and have been investigated in detail by many researchers. − Through experimental exploration and numerical simulations, the primary breakup process of Newtonian fluids is governed by air–liquid interface instabilities. Many factors affect the performance of primary breakup, such as injection pressure, nozzle geometry, and liquid properties. − To describe the magnitude of surface tension and aerodynamic force, Weber proposed a dimensionless number We = ρ g ( u g – u l ) 2 D l /σ, where ρ g is the air density, u g is the air velocity, u l is the liquid velocity, D l is the exit diameter of the liquid jet, and σ is the surface tension. The viscosity of the working liquid also influences the primary breakup process. , Another important dimensionless number is the ratio of gas-to-liquid momentum flux M = ρ g u g 2 /ρ l u l 2 , proposed by Leroux et al, where ρ l is the density of the liquid jet.…”