Binary-fluid turbulence: Signatures of multifractal droplet dynamics and dissipation reduction

Pal, Nairita; Perlekar, Prasad; Gupta, A.; Pandit, Rahul

doi:10.1103/physreve.93.063115

Cited by 17 publications

(15 citation statements)

References 71 publications

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“…In addition, the external forcing properties f 0A,φ , and k f A,φ are also adjustable. Important dimensionless numbers here are as follows [25,31]: (4) Ch = ξ/L 0 , the Cahn number, which is the ratio of the interfacial thickness to the system size.…”

Section: A Basic Setupmentioning

confidence: 99%

Cascades and spectra of a turbulent spinodal decomposition in two-dimensional symmetric binary liquid mixtures

et al. 2016

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We study the fundamental physics of cascades and spectra in two-dimensional (2D) Cahn-Hilliard-Navier-Stokes (CHNS) turbulence, and compare and contrast this system with 2D magnetohydrodynamic (MHD) turbulence. The important similarities include basic equations, ideal quadratic invariants, cascades, and the role of linear elastic waves. Surface tension induces elasticity, and the balance between surface tension energy and turbulent kinetic energy determines a length scale (Hinze scale) of the system. The Hinze scale may be thought of as the scale of emergent critical balance between fluid straining and elastic restoring forces. The scales between the Hinze scale and dissipation scale constitute the elastic range of the 2D CHNS system. By direct numerical simulation, we find that in the elastic range, the mean square concentration spectrum H ψ k of the 2D CHNS system exhibits the same power law (−7/3) as the mean square magnetic potential spectrum H A k in the inverse cascade regime of 2D MHD. This power law is consistent with an inverse cascade of H ψ , which is observed. The kinetic energy spectrum of the 2D CHNS system is E K k ∼ k −3 if forced at large scale, suggestive of the direct enstrophy cascade power law of 2D Navier-Stokes turbulence. The difference from the energy spectra of 2D MHD turbulence implies that the back reaction of the concentration field to fluid motion is limited. We suggest this is because the surface tension back reaction is significant only in the interfacial regions. The interfacial regions fill only a small portion of the 2D CHNS system, and their interface packing fraction is much smaller than that for 2D MHD.

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Section: A Basic Setupmentioning

confidence: 99%

Cascades and spectra of a turbulent spinodal decomposition in two-dimensional symmetric binary liquid mixtures

et al. 2016

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“…A recent study [44] has suggested that the SARS-CoV-2 virus remains viable in aerosols for nearly 3 h. Therefore, if the concentration of virus-laden aerosols is high in a poorly ventilated room, then we must employ more stringent socialdistancing norms than are in place now, even if people spend only tens of minutes together in such a room. The methods that we have developed can be applied, mutatis mutandis, (a) in sophisticated models for virus particles or droplets, e.g., those that use inertial particles [45,46] or multiphase flows [47,48], and (b) in turbulent flows that are not statistically homogeneous and isotropic. We will examine these in future work.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

First-passage-time problem for tracers in turbulent flows applied to virus spreading

Verma

Bhatnagar

Mitra

et al. 2020

Phys. Rev. Research

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We study the spreading of viruses, such as SARS-CoV-2, by airborne aerosols, via a 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 for the first time. We obtain the probability distribution function P (R, t R) and show that it displays two qualitatively different behaviors: (a) for R L I , P (R, t R) has a power-law tail ∼t −α R , with the exponent α = 4 and L I the integral scale of the turbulent flow; (b) for L I R, the tail of P (R, t R) decays exponentially. We develop models that allow us to obtain these asymptotic behaviors analytically. We show how to use 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.

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“…An interplay between different phases is seen in many different terrestrial and astrophysical systems across a vast range of scales. This includes interactions between water vapour and air in the earth's atmosphere (Aronovitz & Nelson 1984;Pal et al 2016), the interface between hot and cold air in combustion (Bray & Cant 1991), solar corona mass ejections, loops, and coronal rain (Foullon et al 2011(Foullon et al , 2013Antolin 2020), warm and hot phases of the interstellar medium (ISM) (Begelman & Fabian 1990;Slavin et al 1993;Wolfire et al 1995a;Vázquez-Semadeni et al 2000;Audit & Hennebelle 2005;Hennebelle & Audit 2007;Glover et al 2010), neutral molecular/atomic, nebular and hot X-ray emitting regions in the Milky Way's wind (Fox et al 2015;Bordoloi et al 2017;Di Teodoro et al 2020), the circumgalactic medium (CGM) (Wolfire et al 1995b;Tumlinson et al 2011;Werk et al 2014;Tumlinson et al 2017;Marchal et al 2021) and the intracluster medium (ICM) (Tremblay et al ★ E-mail: rajsekhar.mohapatra@anu.edu.au (RM) † E-mail:mrinaljetti@gmail.com (MJ) ‡ E-mail: prateek@iisc.ac.in (PS) § E-mail: christoph.federrath@anu.edu.au (CF) 2018; Gendron-Marsolais et al 2018;Olivares et al 2019;Boselli et al 2019;Rose et al 2019;Vantyghem et al 2019Vantyghem et al , 2021. The mixing between these different phases is often governed by turbulent gas motions.…”

Section: Introductionmentioning

confidence: 99%

Characterising the turbulent multiphase halos with periodic box simulations

Mohapatra,

Jetti,

Sharma

et al. 2021

Preprint

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Turbulence in the intracluster medium (ICM) is driven by active galactic nuclei (AGNs) jets, by mergers, and in the wakes of infalling galaxies. It not only governs gas motion but also plays a key role in the ICM thermodynamics. Turbulence can help seed thermal instability by generating density fluctuations, and mix the hot and cold phases together to produce intermediate temperature gas (10 4 -10 7 K) with short cooling times. We conduct high resolution (384 3 -768 3 resolution elements) idealised simulations of the multiphase ICM and study the effects of turbulence strength, characterised by 𝑓 turb (0.001-1.0), the ratio of turbulent forcing power to the net radiative cooling rate. We analyse density and temperature distribution, amplitude and nature of gas perturbations, and probability of transitions across the temperature phases. We also study the effects of mass and volume weighted thermal heating and weak ICM magnetic fields. For low 𝑓 turb , the gas is distribution is bimodal between the hot and cold phases. The mixing between different phases becomes more efficient with increasing 𝑓 turb , producing larger amounts of the intermediate temperature gas. Strong turbulence ( 𝑓 turb ≥ 0.5) generates larger density fluctuations and faster cooling, and ultimately supersonic gas motions. The rms logarithmic pressure fluctuation scaling with Mach number 𝜎 2 ln P ≈ ln 1 + 𝑏 2 𝛾 2 M 4 is unaffected by thermal instability and is the same as in hydro turbulence. In contrast, the density fluctuations characterised by 𝜎 2 𝑠 are much larger, especially for M 0.5. In magnetohydrodynamic runs, magnetic fields provide significant pressure support in the cold phase but do not have any strong effects on the diffuse gas distribution, and nature and amplitude of fluctuations.

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Binary-fluid turbulence: Signatures of multifractal droplet dynamics and dissipation reduction

Cited by 17 publications

References 71 publications

Cascades and spectra of a turbulent spinodal decomposition in two-dimensional symmetric binary liquid mixtures

Cascades and spectra of a turbulent spinodal decomposition in two-dimensional symmetric binary liquid mixtures

First-passage-time problem for tracers in turbulent flows applied to virus spreading

Characterising the turbulent multiphase halos with periodic box simulations

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