Direct numerical simulation of turbulent mixing

Abstract

One contribution of 13 to a Theme Issue 'Turbulent mixing and beyond: non-equilibrium processes from atomistic to astrophysical scales II' . The results of three-dimensional numerical simulations of turbulent flows obtained by various authors are reviewed. The paper considers the turbulent mixing (TM) process caused by the development of the main types of instabilities: those due to gravitation (with either a fixed or an alternating-sign acceleration), shift and shock waves. The problem of a buoyant jet is described as an example of the mixed-type problem. Comparison is made with experimental data on the TM zone width, profiles of density, velocity and turbulent energy and degree of homogeneity.

Rayleigh–Taylor mixing: direct numerical simulation and implicit large eddy simulation

“…The spike to bubble ratio, / s b h h , was estimated and found to be significantly less at high Atwood number than reported for the immiscible-fluid experiments of Dimonte and Schnieder (2000). The review paper, Statsenko et al (2013), shows results for the total mixing zone width at density ratios 3:1 to 40:1. The results at 3:1, assumings b h h , indicate ~0.03.…”

“…Variable acceleration, with g alternating in sign was investigated by incompressible ILES, Dimonte et al (2007) and Ramaprabhu et al (2013). Alternating sign acceleration and evolution of RT mixing with an additional localized perturbation was considered in Statsenko et al (2013). In the paper by Olson et al (2011) initial shear is added to investigate the combined effect of Rayleigh-Taylor and Kelvin-Helmholtz instabilities.…”

Turbulent mixing and beyond: non-equilibrium processes from atomistic to astrophysical scales II

“…Statsenko et al [8] review numerical simulations carried out over the last decades on RT and RM instabilities. The authors note that direct numerical simulation (DNS) of some turbulent flows is not affordable even with modern computers and that LES approaches may offer a promising alternative.…”

“…This part II of the Theme Issue consists of the following papers: the paper by Sreenivasan & Abarzhi on acceleration and turbulence in Rayleigh-Taylor (RT) mixing [1]; by Meshkov on experimental studies of unstable interfaces [2]; by Youngs on numerical modelling simulations of self-similar regimes in mixing flows [3]; by Grinstein et al [4] on a pragmatic approach for reproducing complex multiphase flows in simulations; by Glimm et al [5] on the so-called alpha problem; by Nevmerzhitskiy on the implementation and diagnostics of RT/Richtmyer-Meshkov (RM) mixing in experiments [6]; by Livescu on high resolution approaches for numerical modelling of RT instabilities [7]; by Statsenko et al [8] on subgrid scale models applied to RT/RM mixing; by Prestridge et al analysing the RM mixing experiments conducted over the past decade [9]; by Levitas on mixing applications in reactive flows [10]; by Pudritz & Kevlahan on supersonic processes and shock waves in interstellar media [11]; and by Anisimov et al [12] summarizing the status of our understanding of RT mixing. We observe the development of the Rayleigh-Taylor instability (RTI) when fluids of different densities are accelerated against the density gradient [13,14].…”