A5023352257- Fluid Dynamics and Turbulent Flows
- Solar and Space Plasma Dynamics
- Particle Dynamics in Fluid Flows
- Geomagnetism and Paleomagnetism Studies
- Astro and Planetary Science
- Aeolian processes and effects
- Rheology and Fluid Dynamics Studies
- Ionosphere and magnetosphere dynamics
- Micro and Nano Robotics
- Geophysics and Gravity Measurements
- Complex Systems and Time Series Analysis
- Theoretical and Computational Physics
- Blood properties and coagulation
- Ocean Waves and Remote Sensing
- Lattice Boltzmann Simulation Studies
- Advanced Thermodynamics and Statistical Mechanics
- Granular flow and fluidized beds
- Climate variability and models
- Astrophysics and Star Formation Studies
- Force Microscopy Techniques and Applications
- Wind and Air Flow Studies
- Nonlinear Dynamics and Pattern Formation
- Characterization and Applications of Magnetic Nanoparticles
- Erythrocyte Function and Pathophysiology
- Stellar, planetary, and galactic studies
KTH Royal Institute of Technology
2016-2025
Nordic Institute for Theoretical Physics
2012-2024
Stockholm University
2015-2024
Indian Institute of Science Education and Research Kolkata
2021
TIFR Centre for Interdisciplinary Sciences
2019
AlbaNova
2010-2012
Queen Mary University of London
2007-2010
Observatoire de la Côte d’Azur
2005-2006
Indian Institute of Science Bangalore
1982-2005
Abstract Elastic turbulence is the chaotic fluid motion resulting from elastic instabilities due to addition of polymers in small concentrations at very Reynolds ( $${{{{{{{\rm{Re}}}}}}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Re</mml:mi> </mml:math> ) numbers. Our direct numerical simulations show that turbulence, though a low phenomenon, has more common with classical, Newtonian than previously thought. In particular, we find power-law spectra for kinetic...
The existence of drag reduction by polymer additives, well established for wall-bounded turbulent flows, is controversial in homogeneous, isotropic turbulence. To settle this controversy we carry out a high-resolution direct numerical simulation (DNS) decaying, turbulence with additives. Our study reveals clear manifestations drag-reduction-type phenomena: On the addition polymers to fluid obtain energy dissipation rate, significant modification spectrum especially deep-dissipation range,...
Shear thickening appears as an increase of the viscosity a dense suspension with shear rate, sometimes sudden and violent at high volume fraction. Its origin for noncolloidal non-negligible inertial effects is still debated. Here we consider simple flow demonstrate that fluid inertia causes strong microstructure anisotropy results in formation shadow region no relative flux particles. We show finite can be explained effective fraction when considering dynamically excluded due to these regions.
Collaboration et al., (2021). The Pencil Code, a modular MPI code for partial differential equations and particles: multipurpose multiuser-maintained. Journal of Open Source Software, 6(58), 2807, https://doi.org/10.21105/joss.02807
We present the first numerical demonstration of negative effective magnetic pressure instability in direct simulations stably stratified, externally forced, isothermal hydromagnetic turbulence regime large plasma beta. By action this instability, initially uniform horizontal field forms flux concentrations whose scale is compared to turbulent scale. further show that energy these large-scale structures only weakly dependent on Reynolds number. Our results support earlier mean-field...
We use direct numerical simulations to study homogeneous and isotropic turbulent flows of dilute polymer solutions at high Reynolds Deborah numbers. find that for small wave numbers k, the kinetic energy spectrum shows Kolmogorov-like behavior crosses over a larger k novel, elastic scaling regime, E(k) ∼ k-ξ, with ξ ≈ 2.3. contribution polymers flux through scales it can be decomposed into two parts: one increase in effective viscous dissipation purely dominates nonlinear range which is...
Self-consistent convective dynamo simulations in wedge-shaped spherical shells are presented. Differential rotation is generated by the interaction of convection with rotation. Equatorward acceleration and action obtained only for sufficiently rapid The angular velocity tends to be constant along cylinders. Oscillatory large-scale fields found migrate poleward direction. Comparison earlier full Cartesian domains made.
Simulations show that a suspension of deformable incompressible spheres in Newtonian fluid displays shear-thinning and this can be understood terms reduction the effective volume fraction occupied by suspended due to their deformation.
Solar flares create adverse space weather impacting and Earth-based technologies. However, the difficulty of forecasting flares, by extension severe weather, is accentuated lack any unique flare trigger or a single physical pathway. Studies indicate that multiple properties contribute to active region potential, compounding challenge. Recent developments in machine learning (ML) have enabled analysis higher-dimensional data leading increasingly better techniques. consensus on high-performing...
We study turbulence in the one-dimensional Burgers equation with a white-in-time, Gaussian random force that has Fourier-space spectrum approximately 1/k, where k is wave number. From very high-resolution numerical simulations, limit of vanishing viscosity, we find evidence for multiscaling velocity structure functions which cannot be falsified by standard tests. new artifact logarithmic corrections can appear disguised as anomalous scaling and conclude bifractal likely.
Abstract We use direct numerical simulations of forced MHD turbulence with a forcing function that produces two different signs kinetic helicity in the upper and lower parts domain. show mean flux magnetic from small‐scale field between domain can be described by Fickian diffusion law coefficient is approximately independent Reynolds number about one third estimated turbulent diffusivity. The data suggest diffusive only expected to alleviate catastrophic quenching at numbers more than...
We present direct numerical simulations of the equations compressible magnetohydrodynamics in a wedge-shaped spherical shell, without shear, but with random helical forcing which has negative (positive) helicity northern (southern) hemisphere. find large-scale magnetic field that is nearly uniform azimuthal direction and approximately antisymmetric about equator. Furthermore, each hemisphere oscillates on dynamical time scales reversals polarity equatorward migration. Corresponding...
We carry out a direct numerical simulation (DNS) study that reveals the effects of polymers on statistically steady, forced, homogeneous, isotropic fluid turbulence. find clear manifestations dissipation-reduction phenomena: On addition to turbulent fluid, we obtain reduction in energy dissipation rate, significant modification spectrum, especially deep-dissipation range, suppression small-scale intermittency, and decrease vorticity filaments. also compare our results with recent experiments...
We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using Okubo-Weiss parameter $\ensuremath{\Lambda}$ to distinguish between vortical and extensional regions. then use direct numerical simulation of two-dimensional, incompressible Navier-Stokes equation with Ekman friction study probability distribution functions (PDFs) times regions employing both Eulerian Lagrangian measurements. find that, case, persistence-time PDFs have exponential...
We present an overview of the statistical properties turbulence in two-dimensional (2D) fluids. After a brief recapitulation well-known results for statistically homogeneous and isotropic 2D fluid turbulence, we give recent progress this field such conducting fluids, fluids with polymer additives, binary-fluid mixtures, superfluids; also discuss particles advected by turbulent
Guided by extensive numerical simulations, we propose a microfluidic device that can sort elastic capsules their deformability. The consists of duct embedded with semi-cylindrical obstacle, and diffuser which further enhances the sorting capability. We demonstrate operate reasonably well under changes in initial position capsule. efficiency remains essentially unaltered small obstacle shape (from semi-circular to semi-elliptic cross-section). Confinement along direction perpendicular plane...
We study the rheology of confined suspensions neutrally buoyant rigid monodisperse spheres in plane-Couette flow using direct numerical simulations. find that if width channel is a (small) integer multiple sphere diameter, self-organize into two-dimensional layers slide on each other and effective viscosity suspension significantly reduced. Each layer found to be structurally liquidlike but its dynamics frozen time.
We perform direct numerical simulations of the flow through a model deformable porous medium. Our is two-dimensional hexagonal lattice, with defects, soft elastic cylindrical pillars, shear modulus $G$, immersed in liquid. use two-phase approach: liquid phase viscous fluid and solid modeled as an incompressible viscoelastic material, whose complete nonlinear structural response considered. observe that Darcy flux ($q$) function -- steeper than linear pressure-difference ($\Delta P$) across...
We provide a minimal strategy for the quantitative analysis of large class non-equilibrium systems in {statistically} steady state using short-time Thermodynamic Uncertainty Relation (TUR). From trajectory data obtained from experiments, we demonstrate how can simultaneously infer quantitatively, both thermodynamic force field acting on system, as well (potentially exact) rate entropy production. benchmark this scheme first an experimental study colloidal particle system where exact...
Abstract The Sun’s activity, which is associated with the solar magnetic cycle, creates a dynamic environment in space known as weather. Severe weather can disrupt space-based and Earth-based technologies. Slow decadal-scale variations on solar-cycle timescales are important for radiative forcing of Earth’s atmosphere impact satellite lifetimes atmospheric dynamics. Predicting cycle therefore critical importance humanity. In this context, novel development application machine-learning...
We consider mean-field dynamo models with fluctuating \alpha effect, both and without shear. The effect is chosen to be Gaussian white noise zero mean given covariance. show analytically that the magnetic field does not grow, but, in an infinitely large domain, mean-squared shows exponential growth of fastest growing mode at a rate proportional shear rate, which agrees earlier numerical results Yousef et al (2008) recent analytical treatment by Heinemann (2011) who use method different from...
As a test bed for the growth of protoplanetary bodies in turbulent circumstellar disk, we examine fate boulder using direct numerical simulations particle seeded gas flowing around it. We provide an accurate description flow by imposing no-slip and non-penetrating boundary conditions on surface immersed method pioneered Peskin. Advected disk flow, dust grains collide with compute probability density function normal component collisional velocity. Through this examination statistics...
In two-dimensional forced Navier-Stokes turbulence, energy cascades to the largest scales in system form a pair of coherent vortices known as Bose condensate. We show, both numerically and analytically, that condensation saturates reaches statistically stationary state. The time scale saturation is inversely proportional viscosity level determined by force. further show that, without sufficient resolution resolve small-scale enstrophy spectrum, numerical simulations can give spurious result...
The elastic properties of nanoscale extracellular vesicles (EVs) are believed to influence their cellular interactions, thus having a profound implication in intercellular communication. However, accurate quantification modulus is challenging due dimensions and fluid-like lipid bilayer. We show that the previous attempts develop atomic force microscopy-based protocol flawed as they lack theoretical underpinning well ignore important contributions arising from surface adhesion forces membrane...