51 citations · 289 across the 43 of their papers we have counts for
44 papers
Competing routes to spontaneous flow in confined active nematics
Rahil N. Valani, Vedad Dzanic, Sumesh P. Thampi +1
Active nematics can spontaneously develop flow beyond a critical activity in confined geometries. We show analytically that the onset of flow is governed by two competing instabili…
An active Lorentz gas: walking droplets in periodic media
Aleksi Majaniemi, Esko Toivonen, Rahil N. Valani +2
The Lorentz gas is a paradigmatic model in dynamical systems theory for understanding the origin of nonequilibrium transport in terms of microscopic deterministic chaos. In the per…
Synchronization induces Bell violations in a model of walking droplets
Álvaro G. López, Rahil N. Valani, Yuanmei Li +1
We consider a reduced Lorenz-like model that describes two walking droplets interacting through their mutual wave field, and investigate the emergence of strong bipartite correlati…
Intermittent Flocking and Fractal Collective Order Induced by Time-Varying Delays
David Müller-Bender, Rahil N. Valani
Time-varying interaction delays are ubiquitous in active matter, yet their collective effects remain largely unexplored. We show that active particles with internal dynamics and Vi…
Longitudinal particle separation
Siluvai Antony Selvan, Rahil N Valani, Brendan Harding +1
Owing to inertial effects, the flow through a three-dimensional curved duct focuses finite-sized spherical particles in the two-dimensional cross-section onto either stable equilib…
Emergent Active Clusters through Wave-Mediated Interactions
Yuanmei Li, Rahil Valani
Collective behaviour in active matter usually emerges from interactions between individually stable units. Here we demonstrate a different route to collective organization using dr…
Shear-Induced Collective Shape Oscillations in Dense Soft Suspensions
Ioannis Hadjifrangiskou, Rahil N. Valani, Diogo E. P. Pinto
Dense suspensions of deformable particles can exhibit rich nonequilibrium dynamics arising from complex flow-structure coupling. Using a multi-phase field model, we show that stead…
Active Soft-Impact Oscillator: Dynamics of a Walking Droplet in a Non-Smooth Potential
Titir Mukherjee, Rahil N Valani, Soumitro Banerjee
Walking droplets are millimetric fluid drops that propel themselves across a vibrated liquid bath through interaction with their self-generated waves. They constitute classical act…
Intermittent Motility of a Synthetic Active Particle in Changing Environments
Rudra Sekhri, Rahil N. Valani, Tapio Simula
We experimentally investigate the dynamics of synthetic active particles composed of gravitationally bouncing, superwalking droplets confined within an annular fluid bath. Driven b…
Wave-Like Statistics from Classical Active Particles with Internal Degrees Of Freedom
Rahil N. Valani
Wave-like spatial statistics in walking-droplet systems are often associated with wave-mediated interactions and wave-memory effects. Here we explore how similar statistical struct…
From Equilibrium Multistability to Spatiotemporal Chaos in Channel Flows of Nematic Fluids
Rahil N. Valani, Sumesh Thampi, Julia M. Yeomans
We investigate channel-confined, nematic liquid crystals using the Beris-Edwards model of nematohydrodynamics. Using strong homeotropic anchoring at the walls, we find multistabili…
A Hamiltonian formulation for the motion of an active spheroidal particle suspended in laminar straight duct flow
Brendan Harding, Rahil N. Valani, Yvonne M. Stokes
We analyse a generalisation of Zöttl and Stark's model of active spherical particles [Phys. Rev. Lett. 108, 218104 (2012)] and prolate spheroidal particles [Eur. Phys. J. E 36(1),…
Energy self-balance as the physical basis of orbit quantization
Álvaro G. López, Rahil N. Valani
We show that work done by the non conservative forces along a stable limit cycle attractor of a dissipative dynamical system is always equal to zero. Thus, mechanical energy is pre…
Laminar chaos in systems with random and chaotically time-varying delay
David Müller-Bender, Rahil N. Valani
A type of chaos called laminar chaos was found in singularly perturbed dynamical systems with periodically [Phys. Rev. Lett. 120, 084102 (2018)] and quasiperiodically [Phys. Rev. E…
Active wave-particle clusters
Rahil N. Valani, David M. Paganin
Active particles are non-equilibrium entities that uptake energy and convert it into self-propulsion. A dynamically rich class of inertial active particles having features of wave-…
Nematic order from phase synchronization of shape oscillations
Ioannis Hadjifrangiskou, Sumesh P. Thampi, Rahil N. Valani
We show that a suspension of non-interacting deformable particles subjected to an oscillatory shear flow leads to development of nematic order that arises from the phenomenon of ph…
Hydrodynamic memory and Quincke rotation
Jason K. Kabarowski, Aditya S. Khair, Rahil N. Valani
The spontaneous (so-called Quincke) rotation of an uncharged, solid, dielectric, spherical particle under a steady electric field is analyzed, accounting for the inertia of the par…
Megastable quantization in generalized pilot-wave hydrodynamics
Álvaro G. López, Rahil N. Valani
A classical particle in a harmonic potential gives rise to a continuous energy spectra, whereas the corresponding quantum particle exhibits countably infinite quantized energy leve…
Tunneling in a Lorenz-like model for an active wave-particle entity
Runze Xu, Rahil N. Valani
Active wave-particle entities (WPEs) emerge as self-propelled oil droplets on the free surface of a vibrating oil bath. The particle (droplet) periodically imprints decaying waves…
Asymmetric limit cycles within Lorenz chaos induce anomalous mobility for a memory-driven active particle
Rahil N. Valani, Bruno S. Dandogbessi
On applying a small bias force, non-equilibrium systems may respond in paradoxical ways such as with giant negative mobility (GNM) -- a large net drift opposite to the applied bias…
Active particle motion in Poiseuille flow through rectangular channels
Rahil N. Valani, Brendan Harding, Yvonne M. Stokes
We investigate the dynamics of a point-like active particle suspended in fluid flow through a straight channel. For this particle-fluid system, we derive a constant of motion for a…
Driven transitions between megastable quantized orbits
Álvaro G. López, Rahil N. Valani
We consider a nonlinear oscillator with state-dependent time-delay that displays a countably infinite number of nested limit cycle attractors, \emph{i.e.} megastability. In the low…
Inertial particle focusing in fluid flow through spiral ducts: dynamics, tipping phenomena and particle separation
Rahil N. Valani, Brendan Harding, Yvonne M. Stokes
Small finite-size particles suspended in fluid flow through an enclosed curved duct can focus to points or periodic orbits in the two-dimensional duct cross-section. This particle…
Markovian Embedding of Nonlinear Memory via Spectral Representation
Divya Jaganathan, Rahil N. Valani
Differential equations containing memory terms that depend nonlinearly on past states model a variety of non-Markovian processes. In this study, we present a Markovian embedding pr…