RESEARCH
My research interests are listed under three main projects where the details can be found below:
Homogeneous variabledensity 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 variabledensity (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 buoyancydriven homogeneous variabledensity turbulence by highresolution Direct Numerical Simulations (DNS) in triplyperiodic 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).
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HVDT flow evolution at highdensity 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 buoyancydriven homogeneous variabledensity turbulence”, J. Fluid Mech. 895, A12 (2020).

Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Variabledensity buoyancydriven 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 buoyancydriven variabledensity 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 variabledensity 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 buoyancydriven homogeneous variabledensity turbulence”, Los Alamos National Laboratory Invited talk, COMUEX Talks, Los Alamos, NM (September 2018).

Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Variabledensity 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, “Densityratio effects on buoyancydriven variabledensity turbulent mixing.”, American Physical Society  Division of Fluid Dynamics, Denver, CO (November, 2017).

Denis Aslangil, Daniel Livescu and Arindam Banerjee, “HighAtwood number effects on buoyancydriven 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).
variabledensity turbulencE
Theory
The validity of Boussinesq approximation
The roughness properties of density and velocity fields of Variabledensity turbulence
Energy cascade mechanism in variabledensity turbulence
modeling
Twopoint spectral turbulence and
mix model.
Improvement of LES, hybrid RANS/LES methods for variabledensity 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, “Twopoint spectral model for variabledensity homogeneous turbulence” Phys. Rev. Fluids 3, 124608 (2018).

Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Acceleration reversal effects on buoyancydriven variabledensity turbulence”, (under review) proceedings of the 22nd Australasian Fluid Mechanics Conference, (2020).

Denis Aslangil, Daniel Livescu and Arindam Banerjee, “NonBoussinesq effects on buoyancydriven variabledensity turbulence”, (under review) Journal of Fluid Mechanics (2020).

Denis Aslangil, Daniel Livescu and Arindam Banerjee, “Exact KarmanHowarthMonin (KHM) equation for variabledensity turbulence”, (in preparation) to be submitted to Journal of Fluid Mechanics (June, 2020).

Denis Aslangil, Juan A. Saenz and Daniel Livescu, L04.00005, “Filterwidth 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, “NonBoussinesq effects on buoyancydriven variabledensity turbulence.”, Arizona and Los Alamos Days, Tucson, AZ (April 2019).
Rayleightaylor instability (RTI) under variable acceleration histories
Classical RTI
Constant acceleration*
RTI Under variable acceleration histories*
RayleighTaylor 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 everlarger 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, "RayleighTaylor 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 RayleighTaylor 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 latetime 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 latetime evolution to turbulence of Rayleigh Taylor instability under variable acceleration histories", Int. Centre for Theoretical PhysicsTurbulent 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).