The aim of this Letter is to characterize the flow regimes suspensions finite-size rigid particles in a viscous fluid at finite inertia. We explore system behavior as function particle volume fraction and Reynolds number (the ratio inertia forces). Unlike single-phase flows, where clear distinction exists between laminar turbulent states, three different can be identified presence particulate phase, with smooth transitions them. At low fractions, becomes when increasing number, transitioning...

Abstract We study the modal and non-modal linear instability of inertia-dominated channel flow viscoelastic fluids modelled by Oldroyd-B FENE-P closures. The effects polymer viscosity relaxation time are considered for both fluids, with additional parameter maximum possible extension FENE-P. find that explaining effect on is ratio between characteristic scale (the frequency a wave over which disturbance grows in case). Destabilization observed when shorter than scale, whereas more stable...

Abstract The first bifurcation and the instability mechanisms of shear-thinning shear-thickening fluids flowing past a circular cylinder are studied using linear theory numerical simulations. Structural sensitivity analysis based on idea ‘wavemaker’ is performed to identify core instability. shear-dependent viscosity modelled by Carreau model where rheological parameters, i.e. power-index material time constant, chosen in range $0. 4\leq n\leq 1. 75$ 1\leq \lambda \leq 100$ . We show how...

Abstract The bifurcations and control of the flow in a planar X-junction are studied via linear stability analysis direct numerical simulations. This study reveals instability mechanisms symmetric channel junction shows how these can be stabilized or destabilized by boundary modification. We observe two as Reynolds number increases. They both scale with inlet speed side channels almost independent main channel. Equivalently, appear when recirculation zones reach critical length. A...

Direct numerical simulations of the fully developed turbulent flow through a porous square duct are performed to study effect permeable wall on secondary cross-stream flow. The volume-averaged Navier–Stokes equations used describe in phase, packed bed with porosity ${\it\varepsilon}_{c}=0.95$ . is computed at $\mathit{Re}_{b}\simeq 5000$ and compared four solid walls. two boundary layers top interface merge close centre duct, as opposed channel, because sidewall inhibit growth shear layer...

We study numerically the inertial migration of a single rigid sphere and an oblate spheroid in straight square rectangular ducts. A highly accurate interface-resolved numerical algorithm is employed to analyse entire dynamics particle compare it with that sphere. Similarly focusing spheres, reaches one four face-centred equilibrium positions, however they are vertically aligned axis symmetry spanwise direction. In addition, lateral trajectories spheres oblates collapse into manifold before...

The shear-induced deformation of a capsule with stiff nucleus, model eukaryotic cells, is studied numerically. membrane the cell and its nucleus are modelled as thin impermeable elastic material obeying Neo-Hookean constitutive law. membranes discretised by Lagrangian mesh their governing equations solved in spectral space using spherical harmonics, while fluid on staggered grid second-order finite differences scheme. fluid-structure coupling obtained an immersed boundary method. numerical...

We present a numerical study of non-colloidal spherical and rigid particles suspended in Newtonian, shear thinning thickening fluids employing an immersed boundary method. consider linear Couette configuration to explore wide range solid volume fractions ( $0.1\leqslant \unicode[STIX]{x1D6F7}\leqslant 0.4$ ) particle Reynolds numbers Re_{p}\leqslant 10$ ). report the distribution fluid phase velocity fraction show that close boundaries inertial effects result significant slip between phase....

We study the transition to turbulence of channel flow finite-size particle suspensions at low volume fraction, i.e., Φ≈0.001. The critical Reynolds number above which is sustained reduces Re≈1675, in presence few particles, independently initial condition, a value lower than that corresponding single-phase flow, Re≈1775. In dilute suspension, arrangement particles important trigger fixed and fraction. As single phase flows, streamwise elongated disturbances are initially induced flow. If can...

We study turbulent channel flow of a binary mixture finite-sized neutrally buoyant rigid particles by means interface-resolved direct numerical simulations. fix the bulk Reynolds number and total solid volume fraction, $Re_{b}=5600$ $\unicode[STIX]{x1D6F7}=20\,\%$ , vary relative fraction small large particles. The consists two different sizes, $2h/d_{l}=20$ $2h/d_{s}=30$ where $h$ is half-channel height $d_{l}$ $d_{s}$ diameters While particulate statistics exhibit significant alteration...

We study the transition from laminar to turbulent flow in a channel seeded with finite-size neutrally buoyant particles.A fixed ratio of 10 between height and particle diameter is considered.The examined range Reynolds numbers 500 ≤ Re 5000 volume fractions 0.001 Φ 0.3.We report non-monotonic behavior threshold value number above which becomes turbulent, agreement previous experimental studies.The mean square velocity fluctuations shear stress fluid phase are reduced by increasing fraction...