Esteban D. Gonzalez-Juez

ODTLES simulations of wall-bounded flows

ODTLES is a novel multi-scale model for 3D turbulent flow based on the one-dimensional-turbulence model of Kerstein [“One-dimensional turbulence: Model formulation and application to homogeneous turbulence, shear flows, and buoyant stratified flows,” J. Fluid Mech. 392, 277 (1999)]. Its key distinction is that it is formulated to resolve small-scale phenomena and capture some 3D large-scale features of the flow with affordable simulations. The present work demonstrates this capability by considering four types of wall-bounded turbulent flows. This work shows that spatial profiles of various flow quantities predicted with ODTLES agree fairly well with those from direct numerical simulations. It also shows that ODTLES resolves the near-wall region, while capturing the following 3D flow features: the mechanism increasing tangential velocity fluctuations near a free-slip wall, the large-scale recirculation region in lid-driven cavity flow, and the secondary flow in square duct flow.

Vertical mixing in homogeneous sheared stratified turbulence: A one-dimensional-turbulence study

We conduct a parametric study of diapycnal mixing using one-dimensional-turbulence (ODT) simulations. Homogeneous sheared stratified turbulence is considered. ODT simulations reproduce the intermediate and energetic regimes of mixing, in agreement with previous work, but do not capture important physics of the diffusive regime. ODT indicates Kρ~ɛ/N2 for the intermediate regime, and Kρ~(ɛh4)1/3 for the energetic regime and limit of near-zero stratification. Here Kρ is the turbulent diffusivity for mass, ɛ the dissipation rate, N the buoyancy frequency, and h the computational domain height, where h is relevant mainly in simulations with jump-periodic vertical boundary conditions. These scaling relationships suggest that Kρ is independent of the molecular diffusivity. ODT results for a wide range of parameters show that Kρ cannot be parametrized solely with the turbulent intensity parameter ɛ/(νN2), in contrast with the previous studies, but it is well predicted by correlations using the Ellison length scale.

Reactive Rayleigh–Taylor turbulent mixing: a one-dimensional-turbulence study

We study the problem of reactive Rayleigh–Taylor turbulence in the Boussinesq framework using one-dimensional-turbulence (ODT) simulations. In this problem a reaction zone between overlying heavy/cold reactants and underlying light/hot products moves against gravity. First, we show that ODT results for global quantities in non-reactive Rayleigh–Taylor turbulence are within those from direct numerical simulations (DNS). This comparison give us confidence in using ODT to study unexplored flow regimes in the reactive case. Then, we show how ODT predicts an early stage of reactive Rayleigh–Taylor turbulence that behaves similarly to the non-reactive case, as observed in previous DNS. More importantly, ODT indicates a later stage where the growth of the reaction zone reduces considerably. The present work can be seen as a step towards the study of supernova flames with ODT.

An analysis of the basic assumptions of turbulent combustion models with emphasis on high-speed flows

This paper outlines the basic assumptions made by several turbulent combustion models and then, using this outline, it analyzes the models’ capabilities and limitations to capture partial-premixing, multiple-feed streams, distributed-reaction-like regimes, extinction/reignition, and high-speed effects (i.e., compressibility effects and viscous heating). These physical phenomena are considered because they are relevant to the design and offdesign operation of aero-turbine engines, augmentors/afterburners, ramjets, and scramjets, and lie at the frontier of the current capabilities of turbulent combustion models. Particular emphasis is made on showing how high-speed effects enter into the models’ formulations.

Effect of the turbulence modeling in large-eddy simulations of nonpremixed flames undergoing extinction and reignition

Simulating practical combustion systems requires the approximation of the interaction between turbulence, molecular transport and chemical reactions. Turbulent combustion models are used for this purpose, but their behavior is difficult to anticipate based on their mathematical formulations, making the use of numerical experimentation necessary. Therefore, the present work explores the effect of three turbulent-combustion models, two eddy-viscosity models, and their parameters on a combustion problem which is notoriously difficult to model: flame extinction and reignition. For this purpose, two types of temporal jets are considered, and direct-numerical-simulation results are compared qualitatively with those from large-eddy simulations.