13 results on '"Mitra, Dhrubaditya"'
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2. Active buckling of pressurized spherical shells : Monte Carlo Simulation
- Author
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Agrawal, Vipin, Pandey, Vikash, and Mitra, Dhrubaditya
- Subjects
Condensed Matter - Soft Condensed Matter ,Condensed Matter - Statistical Mechanics - Abstract
We study the buckling of pressurized spherical shells by Monte Carlo simulations in which the detailed balance is explicitly broken -- thereby driving the shell active, out of thermal equilibrium. Such a shell typically has either higher (active) or lower (quiescent) fluctuations compared to one in thermal equilibrium depending on how the detailed balance is broken. We show that for the same set of elastic parameters, a shell that is not buckled in thermal equilibrium can be buckled if turned active. Similarly, a shell that is buckled in thermal equilibrium can unbuckle if turned quiescent. Based on this result, we suggest that it is possible to experimentally design microscopic elastic shells whose buckling can be optically controlled., Comment: 10 pages, 8 figures, 2 table
- Published
- 2022
- Full Text
- View/download PDF
3. Dynamic multiscaling in stochastically forced Burgers turbulence
- Author
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De, Sadhitro, Mitra, Dhrubaditya, and Pandit, Rahul
- Subjects
Condensed Matter - Statistical Mechanics ,Nonlinear Sciences - Chaotic Dynamics ,Physics - Fluid Dynamics - Abstract
We carry out a detailed study of dynamic multiscaling in the turbulent nonequilibrium, but statistically steady, state of the stochastically forced one-dimensional Burgers equation. We introduce the concept of $\textit{interval collapse times}$ $\tau_{\rm col}$, the time taken for an interval of length $\ell$, demarcated by a pair of Lagrangian tracers, to collapse at a shock. By calculating the dynamic scaling exponent of the order-$p$ moment of $\tau_{\rm col}$, we show that (a) there is $\textit{not one but an infinity of characteristic time scales}$ and (b) the probability distribution function of $\tau_{\rm col}$ is non-Gaussian and has a power-law tail. Our study is based on (a) a theoretical framework that allows us to obtain dynamic-multiscaling exponents analytically, (b) extensive direct numerical simulations, and (c) a careful comparison of the results of (a) and (b). We discuss possible generalizations of our work to dimensions $d >1 $, for the stochastically forced Burgers equation, and to other compressible flows that exhibit turbulence with shocks.
- Published
- 2022
4. Coagulation drives turbulence in binary fluid mixtures
- Author
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Bhatnagar, Akshay, Perlekar, Prasad, and Mitra, Dhrubaditya
- Subjects
Condensed Matter - Statistical Mechanics - Abstract
We use direct numerical simulations and scaling arguments to study coarsening in binary fluid mixtures with a conserved order parameter in the droplet-spinodal regime -- the volume fraction of the droplets is neither too small nor symmetric -- for small diffusivity and viscosity. Coagulation of droplets drives a turbulent flow that eventually decays. We uncover a novel coarsening mechanism, driven by turbulence where the characteristic length scale of the flow is different from the characteristic length scale of droplets, giving rise to a domain growth law of $t^{1/2}$, where $t$ is time. At intermediate times, both the flow and the droplets form self-similar structures: the structure factor $S(q) \sim q^{-2}$ and the kinetic energy spectra $E(q) \sim q^{-5/3}$ for an intermediate range of $q$, the wavenumber., Comment: 10 pages 7 figures
- Published
- 2021
5. The spreading of viruses by airborne aerosols: lessons from a first-passage-time problem for tracers in turbulent flows
- Author
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Verma, Akhilesh Kumar, Bhatnagar, Akshay, Mitra, Dhrubaditya, and Pandit, Rahul
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Physics - Fluid Dynamics ,Condensed Matter - Statistical Mechanics ,Nonlinear Sciences - Chaotic Dynamics - Abstract
We study the spreading of viruses, such as SARS-CoV-2, by airborne aerosols, via a new first-passage-time problem for Lagrangian tracers that are advected by a turbulent flow: By direct numerical simulations of the three-dimensional (3D) incompressible, Navier-Stokes equation, we obtain the time $t_R$ at which a tracer, initially at the origin of a sphere of radius $R$, crosses the surface of the sphere \textit{for the first time}. We obtain the probability distribution function $\mathcal{P}(R,t_R)$ and show that it displays two qualitatively different behaviors: (a) for $R \ll L_{\rm I}$, $\mathcal{P}(R,t_R)$ has a power-law tail $\sim t_R^{-\alpha}$, with the exponent $\alpha = 4$ and $L_{\rm I}$ the integral scale of the turbulent flow; (b) for $l_{\rm I} \lesssim R $, the tail of $\mathcal{P}(R,t_R)$ decays exponentially. We develop models that allow us to obtain these asymptotic behaviors analytically. We show how to use $\mathcal{P}(R,t_R)$ to develop social-distancing guidelines for the mitigation of the spreading of airborne aerosols with viruses such as SARS-CoV-2.
- Published
- 2020
- Full Text
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6. Statistical Properties of the Intrinsic Geometry of Heavy-particle Trajectories in Two-dimensional, Homogeneous, Isotropic Turbulence
- Author
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Gupta, Anupam, Mitra, Dhrubaditya, Perlekar, Prasad, and Pandit, Rahul
- Subjects
Physics - Fluid Dynamics ,Condensed Matter - Statistical Mechanics ,Mathematical Physics ,Physics - Computational Physics - Abstract
We obtain, by extensive direct numerical simulations, trajectories of heavy inertial particles in two-dimensional, statistically steady, homogeneous, and isotropic turbulent flows, with friction. We show that the probability distribution function $\mathcal{P}(\kappa)$, of the trajectory curvature $\kappa$, is such that, as $\kappa \to \infty$, $\mathcal{P}(\kappa) \sim \kappa^{-h_{\rm r}}$, with $h_{\rm r} = 2.07 \pm 0.09$. The exponent $h_{\rm r}$ is universal, insofar as it is independent of the Stokes number ($\rm{St}$) and the energy-injection wave number. We show that this exponent lies within error bars of their counterparts for trajectories of Lagrangian tracers. We demonstrate that the complexity of heavy-particle trajectories can be characterized by the number $N_{\rm I}(t,{\rm St})$ of inflection points (up until time $t$) in the trajectory and $n_{\rm I} ({\rm St}) \equiv \lim_{t\to\infty} \frac{N_{\rm I} (t,{\rm St})}{t} \sim {\rm St}^{-\Delta}$, where the exponent $\Delta = 0.33 \pm0.02$ is also universal., Comment: submitted to Phys. Rev. Lett. The supplementary information is added as an appendix
- Published
- 2014
7. Spontaneous chiral parity breaking by hydromagnetic buoyancy
- Author
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Chatterjee, Piyali, Mitra, Dhrubaditya, Brandenburg, Axel, and Rheinhardt, Matthias
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Condensed Matter - Statistical Mechanics ,Nonlinear Sciences - Adaptation and Self-Organizing Systems ,Physics - Fluid Dynamics ,Physics - Plasma Physics - Abstract
Evidence for a parity-breaking nature of the magnetic buoyancy instability in a stably stratified gas is reported. In the absence of rotation, no helicity is produced, but the non-helical state is found to be unstable to small helical perturbations during the development of the instability. The parity-breaking nature of an instability in magnetohydrodynamics appears to be the first of its kind and is similar to chiral symmetry breaking in biochemistry. Applications to the production of mean fields in galaxy clusters are being discussed., Comment: consistent with the published version
- Published
- 2010
- Full Text
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8. Persistence Problem in Two-Dimensional Fluid Turbulence
- Author
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Perlekar, Prasad, Ray, Samriddhi Sankar, Mitra, Dhrubaditya, and Pandit, Rahul
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Physics - Fluid Dynamics ,Astrophysics - Solar and Stellar Astrophysics ,Condensed Matter - Statistical Mechanics ,Nonlinear Sciences - Chaotic Dynamics - Abstract
We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using the Okubo-Weiss parameter $\Lambda$ to distinguish between vortical and extensional regions. We then use a direct numerical simulation (DNS) of the two-dimensional, incompressible Navier--Stokes equation with Ekman friction to study probability distribution functions (PDFs) of the persistence times of vortical and extensional regions by employing both Eulerian and Lagrangian measurements. We find that, in the Eulerian case, the persistence-time PDFs have exponential tails; by contrast, this PDF for Lagrangian particles, in vortical regions, has a power-law tail with an exponent $\theta=2.9\pm0.2$., Comment: consistent with the published version
- Published
- 2010
- Full Text
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9. The Universality of Dynamic Multiscaling in Homogeneous, Isotropic Turbulence
- Author
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Ray, Samriddhi Sankar, Mitra, Dhrubaditya, and Pandit, Rahul
- Subjects
Nonlinear Sciences - Chaotic Dynamics ,Condensed Matter - Statistical Mechanics ,Physics - Fluid Dynamics - Abstract
We systematise the study of dynamic multiscaling of time-dependent structure functions in different models of passive-scalar and fluid turbulence. We show that, by suitably normalising these structure functions, we can eliminate their dependence on the origin of time at which we start our measurements and that these normalised structure functions yield the same linear bridge relations that relate the dynamic-multiscaling and equal-time exponents for statistically steady turbulence. We show analytically, for both the Kraichnan Model of passive-scalar turbulence and its shell model analogue, and numerically, for the GOY shell model of fluid turbulence and a shell model for passive-scalar turbulence, that these exponents and bridge relations are the same for statistically steady and decaying turbulence. Thus we provide strong evidence for dynamic universality, i.e., dynamic-multiscaling exponents do not depend on whether the turbulence decays or is statistically steady., Comment: 29 pages, 18 figures. For figures with better resolution, please download the preprint available at the website of the International Collaboration of Turbulence Research
- Published
- 2007
10. Dynamic Multiscaling in Turbulence
- Author
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Pandit, Rahul, Ray, Samriddhi Sankar, and Mitra, Dhrubaditya
- Subjects
Nonlinear Sciences - Chaotic Dynamics ,Condensed Matter - Statistical Mechanics ,Physics - Fluid Dynamics - Abstract
We give an overview of the progress that has been made in recent years in understanding the dynamic multiscaling of homogeneous, isotropic turbulence and related problems. We emphasise the similarity of this problem with the dynamic scaling of time-dependent correlation functions in the vicinity of a critical point in, e.g., a spin system. The universality of dynamic-multiscaling exponents in fluid turbulence is explored by detailed simulations of the GOY shell model for fluid turbulence., Comment: 13 pages, 10 figures, Submitted for the Proceedings of the Statphys 23 Conference
- Published
- 2007
- Full Text
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11. Dynamics of Passive-Scalar Turbulence
- Author
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Mitra, Dhrubaditya and Pandit, Rahul
- Subjects
Nonlinear Sciences - Chaotic Dynamics ,Condensed Matter - Statistical Mechanics - Abstract
We present the first study of the dynamic scaling or multiscaling of passive-scalar and passive-vector turbulence. For the Kraichnan version of passive-scalar and passive-vector turbulence we show analytically, in both Eulerian and quasi-Lagrangian frameworks, that simple dynamic scaling is obtained but with different dynamic exponents. By developing the multifractal model we show that dynamic multiscaling occurs in passive-scalar turbulence only if the advecting velocity field is itself multifractal. We substantiate our results by detailed numerical simulations in shell models of passive-scalar advection., Comment: published version
- Published
- 2004
- Full Text
- View/download PDF
12. Is Multiscaling an Artifact in the Stochastically Forced Burgers Equation?
- Author
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Mitra, Dhrubaditya, Bec, Jeremie, Pandit, Rahul, and Frisch, Uriel
- Subjects
Nonlinear Sciences - Chaotic Dynamics ,Condensed Matter - Statistical Mechanics ,Mathematics - Analysis of PDEs - Abstract
We study turbulence in the one-dimensional Burgers equation with a white-in-time, Gaussian random force that has a Fourier-space spectrum $\sim 1/k$, where $k$ is the wave number. From very-high-resolution numerical simulations, in the limit of vanishing viscosity, we find evidence for multiscaling of velocity structure functions which cannot be falsified by standard tests. We find a new artifact in which logarithmic corrections can appear disguised as anomalous scaling and conclude that bifractal scaling is likely., Comment: previous version replaced, with major changes
- Published
- 2004
- Full Text
- View/download PDF
13. Dynamic multiscaling in stochastically forced Burgers turbulence
- Author
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De, Sadhitro, Mitra, Dhrubaditya, and Pandit, Rahul
- Subjects
Multidisciplinary ,Statistical Mechanics (cond-mat.stat-mech) ,Fluid Dynamics (physics.flu-dyn) ,FOS: Physical sciences ,Physics - Fluid Dynamics ,Chaotic Dynamics (nlin.CD) ,Nonlinear Sciences - Chaotic Dynamics ,Condensed Matter - Statistical Mechanics - Abstract
We carry out a detailed study of dynamic multiscaling in the turbulent nonequilibrium, but statistically steady, state of the stochastically forced one-dimensional Burgers equation. We introduce the concept of interval collapse time, which we define as the time taken for a spatial interval, demarcated by a pair of Lagrangian tracers, to collapse at a shock. By calculating the dynamic scaling exponents of the moments of various orders of these interval collapse times, we show that (a) there is not one but an infinity of characteristic time scales and (b) the probability distribution function of the interval collapse times is non-Gaussian and has a power-law tail. Our study is based on (a) a theoretical framework that allows us to obtain dynamic-multiscaling exponents analytically, (b) extensive direct numerical simulations, and (c) a careful comparison of the results of (a) and (b). We discuss possible generalizations of our work to higher dimensions, for the stochastically forced Burgers equation, and to other compressible flows that exhibit turbulence with shocks.
- Published
- 2023
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