RESEARCH

My research interests are listed under three main projects where the details can be found below:

Homogeneous variable-density turbulence

- Turbulent mixing

- High Re numbers and density ratios

- Direct numerical simulations

Variable-density turbulence

         - Theory

         - Modeling

         - Machine Learning

Rayleigh-Taylor instability under variable-acceleration

 - Rayleigh-Taylor instability

 - Dynamic accelration histories

 - ILES

 

Homogeneous variable-density turbulence (HVDT)

Most of the fluids participating in the mixing in applications such as Inertial Confinement Fusion, combustion, or astrophysics have different molar (or atomic) masses. In this case, the dynamic of the flow becomes very different than the single fluid turbulence and the coupled effects of density and velocity fields start to play crucial roles within the flow evolution. In variable-density (VD) flows, the density field acts as an active scalar which changes the whole structure of the flow and it also changes the energy cascade mechanism.

In this project, we investigate buoyancy-driven homogeneous variable-density turbulence  by high-resolution Direct Numerical Simulations (DNS) in triply-periodic domain sizes up to 2048 . HVDT is a canonical fluid flow problem that isolates the VD mixing process from other effects such as compressibility and heat release, as well as inhomogeneities such as mixing layer edges (see Aslangil et al. 2019a,b JFM and Physica D, and the references therein). 

3

HVDT flow evolution at high-density ratios (7 : 1). Please refer to Aslangil et al. 2019 JFM paper for details.

HVDT with asymmetric initial density distributions. Please refer to Aslangil et al. 2019 Physica D paper for details.

  Project Related Publications & Conference abstracts:

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Atwood and Reynolds numbers effects on the evolution of buoyancy-driven homogeneous variable-density turbulence”, J. Fluid Mech. 895, A12 (2020). https://doi.org/10.1017/jfm.2020.268

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Variable-density buoyancy-driven turbulence with asymmetric initial density distribution”, Physica D: Nonlinear Phenomena, 406 132444 (2020). https://doi.org/10.1016/j.physd.2020.132444

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Flow regimes in buoyancy-driven variable-density turbulent”, in: Örlü R., Talamelli A., Peinke J., Oberlack M. (eds) Progress in Turbulence VIII. iTi 2018. Springer Proceedings in Physics, vol 226. Springer, Cham.

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, M01.00040, “Homogeneous variable-density turbulence with asymmetric initial density distributions”, American Physical Society - Division of Fluid Dynamics, Seattle, WA (November, 2019).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Atwood and Reynolds numbers effects on the evolution of buoyancy-driven homogeneous variable-density turbulence”, Los Alamos National Laboratory Invited talk, COMUEX Talks, Los Alamos, NM (September 2018).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Variable-density effects on turbulent mixing.”, International Workshop on the Physics at Compressible Turbulent Mixing 2018, Marseille, France.

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, M29.00008, “Density-ratio effects on buoyancy-driven variable-density turbulent mixing.”, American Physical Society - Division of Fluid Dynamics, Denver, CO (November, 2017).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “High-Atwood number effects on buoyancy-driven variable density homogeneous turbulence.”, European Turbulence Conference, Stockholm, Sweden (August, 2017).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, D40.00003, "Reynolds and Atwood Numbers Effects on Homogeneous Rayleigh Taylor Instability", American Physical Society - Division of Fluid Dynamics, Boston, MA (November, 2015).

 

variable-density turbulencE

Theory

The validity of Boussinesq approximation

The roughness properties of density and velocity fields of Variable-density turbulence

Energy cascade mechanism in variable-density turbulence

modeling

Two-point spectral turbulence and
mix model.

Improvement of LES, hybrid RANS/LES methods for variable-density turbulence

physics informed Machine LeArning

Developing efficient machine learning frameworks to improve the turbulent mixing models, capable to represent all the physics of the real flow.

  Project Related Publications & Conference abstracts:

  • Nairita Pal, Susan Kurien, Timothy Clark, Denis Aslangil and Daniel Livescu, “Two-point spectral model for variable-density homogeneous turbulence” Phys. Rev. Fluids 3, 124608 (2018).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Acceleration reversal effects on buoyancy-driven variable-density turbulence”, (under review) proceedings of the 22nd Australasian Fluid Mechanics Conference, (2020).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Non-Boussinesq effects on buoyancy-driven variable-density turbulence”, (under review) Journal of Fluid Mechanics (2020).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Exact Karman-Howarth-Monin (K-H-M) equation for variable-density turbulence”, (in preparation) to be submitted to Journal of Fluid Mechanics (June, 2020).

  • Denis Aslangil, Juan A. Saenz and Daniel Livescu, L04.00005, “Filter-width and Atwood number effects in filtered homogeneous variable density turbulence”, American Physical Society - Division of Fluid Dynamics, Seattle, WA (November, 2019).

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Non-Boussinesq effects on buoyancy-driven variable-density turbulence.”, Arizona and Los Alamos Days, Tucson, AZ (April 2019).

 

Rayleigh-taylor instability (RTI) under variable acceleration histories

Classical RTI

Constant acceleration*

RTI Under variable acceleration histories*

Rayleigh-Taylor instability (RTI) occurs at a perturbed planar interface between a light fluid and a heavy fluid in the presence of an acceleration field in a direction normal to the interfacial plane. Traditionally, the study of RTI has focused on acceleration fields that are constant and includes various natural and industrial flows such as combustion and chemical reactor processes, pollutant dispersion, certain geological processes, and oceanic current flows. However, there exist several applications in which RTI appears in nonuniform acceleration fields; these include blast waves, inertial confinement fusion, and the stellar dynamics of Type Ia supernovae (see Aslangil et al. 2016 Phys. Rev E, and the references therein).

Variations in acceleration are known to alter the dynamics of the RTI induced mixing process, and our motivations are to investigate the effects of initial conditions, duration of deceleration periods, and the acceleration profiles on the evolution of the instability towards turbulence under acceleration reversals.

* Figures are taken from Aslangil et al. 2016 Phys. Rev. E paper.

Accel
Decel
Accel

TIME

TIME

In the above figures, volume fraction contours of the density field (i) vertical slices taken along the center of the domain and (ii) horizontal slices taken along the interface are presented. Both constant gravity and the ADA profile are shown. As it is seen, the large coherent structures typical of an accelerating flow rapidly disintegrate during deceleration, leaving only smaller scales in the flow and a smaller range of densities. After reacceleration, the flow is RT unstable once more, the mixing layer continues its expansion, bubble and spike structures reemerging and interacting to form ever-larger structures like classical RTI (Aslangil et al. 2016 Phys. Rev E).

  Project Related Publications & Conference abstracts:

  • Denis Aslangil, Zachary Farley, Andrew Lawrie and Arindam Banerjee, "Rayleigh-Taylor Instability with varying periods of zero acceleration" (accepted, in press) J. Fluids Eng. (2020).

  •  Denis Aslangil*, Zachary Farley*, Arindam Banerjee and Andrew Lawrie "On the effects of variable deceleration periods on Rayleigh-Taylor Instability with acceleration reversals", (under review) Phys. Rev. Fluids (2020). *Both authors contributed equally to this manuscript.

  • Denis Aslangil, Arindam Banerjee, and Andrew Lawrie "Numerical investigation of initial condition effects on Rayleigh Taylor instability with acceleration reversals" Phys. Rev. E 94, 053114 (2016).​

  • Denis Aslangil, Daniel Livescu and Arindam Banerjee "Variable density mixing under variable mean pressure gradient acceleration histories", European Turbulence Conference, Delft, Netherlands (August, 2015).

  • Denis Aslangil, Andrew Lawrie and Arindam Banerjee, A22.00006, "Rayleigh Taylor Instability with Acceleration Reversals" American Physical Society - Division of Fluid Dynamics, San Francisco, CA (November, 2014).

  • Denis Aslangil, Andrew Lawrie and Arindam Banerjee "Effect of initial conditions on late-time evolution to turbulence of Rayleigh Taylor instability under variable acceleration histories", International Workshop on the Physics at Compressible Turbulent Mixing, San Francisco, CA (August, 2014).

  • Denis Aslangil, Andrew Lawrie and Arindam Banerjee "Effect of initial conditions on late-time evolution to turbulence of Rayleigh Taylor instability under variable acceleration histories", Int. Centre for Theoretical Physics-Turbulent Mixing and Beyond Workshop, Trieste, Italy (August, 2014).

  • Denis Aslangil, Andrew Lawrie and Arindam Banerjee, L30.00006, "Initial condition effects on turbulent Rayleigh Taylor instability under variable acceleration history.", American Physical Society - Division of Fluid Dynamics, Pittsburgh, PA (November, 2013).

Contact

CCS-2 Computational Physics and Methods,
Computer and Computational Sciences Division,
Mail Stop D413,
Los Alamos National Laboratory
Los Alamos, NM 87545

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Tel       : 505-665-9369

Mobile: 516-849-8910

denis.aslangil@gmail.com

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