The role of chain scission is investigated numerically in the symmetry breaking of the flow of wormlike micellar solutions in a cross-slot geometry.

Large slip coefficients are identified and determined asymptotically in the case of pressure-driven flow between closely spaced superhydrophobic grooved surfaces.

To study intermittency and anomalous scaling of high Reynolds number turbulence, a Lagrangian stochastic differential equation is derived from the gradient of the Navier-Stokes equations using multiple time scales and a closure based on the recent deformation of Gaussian Fields.

Principal component analysis (PCA), developed for combustion applications, is applied to a collisional-radiative two-temperature model for argon plasma, reducing the kinetic system significantly while keeping detailed physics.

We theoretically model the interaction of a non-Newtonian liquid with an elastic cylinder. For shear-thinning fluids, a step in pressure results in compactly supported propagation of deformation. This is in contrast to Stokes’ problem where such propagation is observed in shear thickening fluids.

A numerical method for the Boltzmann transport equation in ultrahigh-vacuum systems is presented in which molecular collisions are neglected, which improves accuracy and convergence time. The method is used to compute particle density in a conical segment for which a density drop is observed at the entrance.

A pair of large bubbles rising side-by-side from rest are studied numerically in 3D. The bubble wakes interact, causing the bubbles to rise in a spiral path. The interaction leads to a mirror symmetry in bubble trajectories which persists for a while even at high inertia when the paths are chaotic.

The simple impact of a viscous drop on a lower-viscosity pool can stretch the drop liquid into thin sheets, which are wrapped and folded into intricate buckled shapes. Particle image velocimetry is used to show that a vortex ring, generated by the viscous stress at the drop-pool interface, drives the convoluted motions.

Cassini observations recently confirmed the existence of a striking distortion of Saturn’s north polar jet into a distinct hexagon. A two-layer statistical state dynamics model closed at second order is used to account for the structure of this Jet, including its hexagonal form.

Gravity currents produced from a two-layer density-stratified source may have varying flow morphologies. Experiments show that the layers can mix or the lower layer may lead from the outset or the upper layer may override the lower layer. These observations are successfully explained by a scaling analysis.

The transitional regime of plane Couette flow is characterised by oblique laminar-turbulent patterns. Their robustness to the presence of wall roughness is investigated numerically using the parametric roughness model of Busse and Sandham.

Topology of localized turbulent coherent structures is studied numerically in transitional regimes of annular Poiseuille flow driven by a fixed pressure gradient. With increasing radius ratio, localized puffs gradually evolve in a helical stripe pattern due to relaxation of azimuthal confinement.

Group Theory and Smoothed Particle Hydrodynamics simulations are used to investigate the effects of the relative phase and the interference of two small waves composing an initial perturbation on the nonlinear dynamics of Richtmyer-Meshkov instabilities

The rotating flow above a flat disc (Bödewadt flow) is shown to stabilize when the disc is radially stretched and destabilize when the disc is shrunk. This surface stretching could also be a suitable mechanism for flow control in other flows configurations.

A self-consistent model is used to analyze the sensitivity of the mean and fluctuating drag and lift on a circular cylinder at Reynolds number that need not be close to the instability threshold. The relevance of computing self-consistent sensitivities from direct numerical simulation data is also discussed.

A theoretical model predicts backward blood spatter from a blunt bullet which favorably agrees with experimental data. Drop generation is explained through the Rayleigh-Taylor instability and includes the effects of air drag and drop-drop interactions.

Imbibition of a liquid into a thin deformable porous substrate driven by capillary suction is studied. Standard shallow-layer scalings are used to construct a reduced dynamical model, which shows qualitative agreement with laboratory experiments using cellulose paper sheets

A propagating viscous gravity current that leaks fluid through a permeable substrate and a fixed edge is studied. Results address the time evolution of the profile shape, the amount of fluid loss through each drainage mechanism, and practical implications for CO${}_2$ sequestration and leakage problems.

A lubricated torque-free cylinder sliding parallel to an elastic substrate is shown to also rotate at steady state using theoretical and numerical approaches. The angular velocity increases with the softness of the substrate.

The linear stability of a thin viscous sheet stretched by extensional flow under an imposed heating profile is studied. Growth rates of unstable modes are found, depending on flow. The instability is shown to be localized in two regions and changes from static to Hopf bifurcation with changing flow.

When typical pore size is below a couple of nanometers, water removal kinetics from an initially wet porous structure varies abruptly. If liquid bursts still allow for liquid motion throughout the entire pore network, vapor removal at the evaporation surface is strongly limited by the Kelvin effect.

Drop collision with a hot, dry solid substrate has been observed and characterized. For a nucleate boiling regime, a heat transfer between the drop and substrate is analyzed. The theoretical predictions for the drop contact time agree well with the experimental data.

Centers of discrete inertial particles transported by turbulence are a Poisson point process with random intensity. Fractal dimensions relevant for processes such as rain formation can be found from sparse data. Large voids have increased probability, enhancing survival in reactions.

A current view is that sediment transport by liquid streams is sustained because fluid forces erode particles resting at the bed surface. Numerical simulations instead show that once transport begins, erosion of resting particles occurs because of impacts of transported particle on the bed surface.

Interaction of a shock wave with an inert dust layer is studied by solving multidimensional sets of Navier-Stokes equations. Forces controlling particle dispersion and dust compaction are examined. The model compares well to experimental shock-tube data where dust first grows and then levels off.

The onset of time dependence is characterized by intermittent bursts during which the spanwise reflection symmetry is broken. Numerical analysis shows that the complex dynamics are organized by two successive subcritical Hopf bifurcations.

A technique for simultaneous measurement of the displacement field of evaporating droplets in a spray and their vapor shows that for a dense spatial dispersion of passively advected droplets slaved to the dynamics of its saturating vapor field, the spray can be described as a scalar mixing problem.

Large eddy simulations (LES) of wind turbine wake recovery depending on wind farm density and atmospheric stratification are presented. We find that harvested power is recovered by two mechanisms, advection and mean kinetic energy flux. A model for the harvested power is developed from the LES data.

Comparing systematically different turbulent flows with a mean shear, at similar Reynolds numbers, reveals a robust structure of the turbulent fluctuations, which does not depend much on the presence of walls. This fundamental property could help in devising parametrization of turbulent shear flows.

Two related buoyancy driven flows are studied: Rayleigh-Taylor and unstably stratified homogeneous turbulence. Small-scale anisotropy of velocity and concentration spectra are found to be dominated by nonlocal contributions of zero-modes rather than by the local action of buoyancy forces.

How do the heat flux and the flow organization change in locally heated, thermally driven turbulence once the liquid is allowed to boil? Experiments show that the heat flux is considerably enhanced and they identify enhanced velocity fluctuations as a major contribution to the enhanced heat flux.

The effect of periodic forcing on bluff-body wake is often divided into low- and high-frequency regimes based on the trends in the re-attachment length. A study shows that vortex-induced momentum entrainment can universally explain the changes to the re-attachment length for all forcing regimes.

Parametric subharmonic instability (PSI) of internal wave beams with nearly twice the inertial frequency due to background rotation in stratified fluid is studied theoretically. Such near-inertial PSI is possible for beams of general profile; generic PSI can arise only for quasimonochromatic beams.