Turbulence is ubiquitous in nature yet even for the case of ordinary Newtonian fluids like water our understanding this phenomenon limited. Many liquids practical importance however are more complicated (e.g. blood, polymer melts or paints), they exhibit elastic as well viscous characteristics and relation between stress strain nonlinear. We here demonstrate a model system such complex that at high shear rates turbulence not simply modified previously believed but it suppressed replaced by...

Significance Bacterial suspensions can flow without apparent viscosity. Such a superfluid-like behavior stems from the collective motions of swimming bacteria. Here, we explore microscopic profile bacterial “superfluids” under simple shear. We find that, instead deforming uniformly, superfluids develop multiple shear bands, i.e., regions with different deformations. construct model that quantitatively describes shape shear-banding structure and reveals important physical properties motions....

Droplets that impact the surface of a deep liquid pool may form vertical jet after cavity formation event, provided they have sufficient energy. Depending on associated time scales and effect Rayleigh Plateau instability, this either continue to rise, or satellite droplets via necking. Collision these structures with second incoming droplet, ejected from same dispensing tip as first result in various lamellar patterns, depending conditions, giving rise mushroom umbrella structures. In...

Droplet impact on liquid films is a ubiquitous phenomenon in nature and many industrial applications. The present study highlights the dynamics of viscoelastic droplets thin water same fluid as droplet. In this experimental study, we have highlighted variations that arise due to non-Newtonian effects. ejection secondary from crown rim normally observed case Newtonian droplet impacts suppressed, films. Due elasticity, Rayleigh–Plateau instability-induced inhibited. Long-lasting slender...

We report an extensive computational and experimental investigation of droplet impact subsequent splitting hydrodynamics on superhydrophobic wedges. Using two-dimensional (2D) three-dimensional (3D) volume-of-fluid (VOF) simulations, supported by high-speed imaging experiments, we predict the impact, spreading, splitting, retraction daughter lift-off from In particular, examine how wedge angle ( ϕ ), asymmetry 1 – 2 Weber number ) normalized Bond Bo * influence post-impact dynamics. observe...

In shear flows, turbulence first occurs in the form of localized structures (puffs/spots) surrounded by laminar fluid. We here investigate such spatially intermittent flows a pipe experiment showing that turbulent puffs have well-defined interaction distance, which sets their minimum spacing as well maximum observable fraction. Two methodologies are employed. Starting from flow, created locally injecting jet fluid through wall. When perturbation is applied periodically at low frequencies,...

Droplet deposition after impact on superhydrophobic surfaces has been an important area of study in recent years for its potential application reduction pesticides usage. Minute numbers long-chain polymers added to water have known arrest the droplet rebound effect surfaces. Previous studies attributed different reasons like extensional viscosity, dominance elastic stresses, or slowing down contact line retraction phase due stretching polymer chains. The present attempts unravel existence...

Droplet impact on a heated substrate is an important area of study in spray cooling applications. On substrates significantly hotter than the saturation temperature, droplets immediately hover its vapor cushion, exhibiting Leidenfrost phenomenon. Here, we report phenomena wherein addition Al2O3 nanoparticles to water increases onset dynamic temperature (TDL) and suppresses overall regime. We experimentally revealed that TDL delays with increasing nanoparticle concentration colloidal...

Droplets may rebound/levitate when deposited over a hot substrate (beyond critical temperature) due to the formation of stable vapor microcushion between droplet and substrate. This is known as Leidenfrost phenomenon. In this article, we experimentally allow droplets impact surface with certain velocity, temperature at which show onset rebound minimal spraying dynamic (TDL). Here propose validate novel paradigm augmenting TDL by employing nanobubbles dispersed in fluid. first-of-its-kind...

This article highlights the role of non-Newtonian (elastic) effects on droplet impact phenomenon at temperatures considerably higher than boiling point, especially or above Leidenfrost regime. The point (LFP) was found to decrease with an increase in Weber number (based velocity just before impact) for fixed polymer (polyacrylamide) concentrations. Water droplets fragmented very low numbers (approx. 22), whereas resisted fragmentation much 155). We also varied concentration and observed...

In this article, we propose, with the aid of detailed experiments and scaling analysis, existence magneto-elastic effects in impact hydrodynamics non-Newtonian ferrofluid droplets on superhydrophobic surfaces presence a magnetic field. The Bond number (

A theoretical exploration and an analytical model for the electro-magneto-hydrodynamics (EMHD) of leaky dielectric liquid droplets suspended in immiscible confined fluid domain have been presented. The solution system, under small deformation approximation creeping flow regime, has put forward. study droplet suggests that its temporal evolution is exponential dependent on electric magnetic field interaction. Furthermore, direction applied relative to determines whether force opposes or...

Using the discrete vortex method we perform numerical simulations of Anguilliform mode swimming dynamics a one-dimensional flexible filament. Various parameters are varied to quantify coefficient thrust and efficiency. We show that wake vortices in Benard--von Karman (BvK) configuration drag producing regime rearrange reverse-BVK (rBvK) when producing. The resultant distribution contour map associated velocity field clarify differences between BvK regime, transition region, rBvK regime....

The present study discusses the numerical simulation results of swimming similar to manta rays. complex three-dimensional kinematics rays were implemented unravel intricacies its propulsion mechanisms by using discrete vortex method (DVM). DVM replaces requirement for a structured grid across computational domain with collection elements. This simplifies generation, especially intricate geometries, resulting in time and effort savings meshing shapes. By modeling pectoral fins panels...

Abstract The study of flow behavior in the simultaneously developing transitional regime mixed convection flows is rare. It has been believed that will give a good compromise between pressure drop and heat transfer compared to laminar turbulent regime. In this experimental study, friction factor (f) Nusselt number (Nu) characteristics for buoyancy-assisted opposed water concurrently through vertical tube are studied. Experiments were done Reynolds numbers (Re) varying from 500 15,000,...

In this article, we report the post-collision elasto-hydrodynamics of non-Newtonian elastic or Boger fluid droplets [polyacrylamide (PAAM) solution in water] on convex cylindrical targets various diameters. Both hydrophilic and superhydrophobic (SH) surfaces were studied to deduce role wettability. Different governing parameters, such as cylinder diameter, Weber number, elasticity (different polymer concentrations), systematically varied understand hydrodynamic outcomes. contrast Newtonian...

In this article, we report the experimental and semi-analytical findings to elucidate electrohydrodynamics (EHD) of a dielectric liquid droplet impact on superhydrophobic (SH) hydrophilic surfaces. A wide range Weber numbers (We) electro-capillary (Cae) are covered explore various regimes EHD. We show that for fixed ∼ 60, rebound SH surface is suppressed with increase in electric field intensity (increase Cae). At high Cae, instead usual uniform radial contraction, droplets retract faster an...