The elasto-inertial focusing and rotating characteristics of spheroids in a square channel flow Oldroyd-B viscoelastic fluids are studied by the direct forcing/fictitious domain method. rotational behaviours, changes equilibrium positions travel distances explored to analyse mechanisms spheroid migration fluids. Within present simulated parameters (1 ≤ Re 100, 0 Wi 2, 0.4 α ≤3), results show that there four kinds six (five) behaviours for prolate (oblate) spheroids. We first identify new...

We study the hydrodynamics of a spherical and dumbbell-shaped microswimmer in tube. Combined with squirmer model generating tangential surface waves for self-propulsion, direct-forcing fictitious domain method is employed to simulate swimming microswimmers. perform simulations by considering variations Reynolds numbers ( Re ), blockage ratios κ ) relative distances d s between squirmers dumbbell. The results show that dumbbell weakens inertia effects fluid more than an individual squirmer....

We investigate the hydrodynamics of a spherical and dumbbell-shaped swimmer in viscoelastic fluid, modelled by Giesekus constitutive equation. The ‘squirmer’, model micro-swimmer with tangential surface waves at its boundaries, is simulated utilizing direct-forcing fictitious domain method. consider competitive effects fluid inertia elasticity on locomotion swimmers. For neutral squirmer, speed increases monotonically increasing Reynolds number contrast to holding constant Newtonian one....

We numerically investigate the hydrodynamics of a spherical swimmer carrying rigid cargo in Newtonian fluid. This model, ‘squirmer’, which is self-propelled by generating tangential surface waves, simulated direct-forcing fictitious domain method (DF-FDM). consider effects swimming Reynolds numbers ( Re ) (based on radius and speed squirmers), assembly models (related to shapes, relative distances d s positions between squirmer cargo) assembly's locomotion. find that ‘pusher-cargo’ (pusher...

The motion of microorganisms in complex fluids stands out as a prominent subject within fluid mechanics. In our study, we utilize the fictitious domain method to investigate locomotion squirmers along convex wall Giesekus viscoelastic fluids. This study examines influence elasticity and curvature on squirmer particles, analyzing their movement patterns detail. Near wall, three distinct behavioral characteristics emerge: scattering, orbiting forward, backward. findings reveal that, compared...

The hydrodynamic behaviours of finite-size microorganisms in turbulent channel flows are investigated using a direct-forcing fictitious domain method. classical ‘squirmer’ model, characterized by self-propulsion through tangential surface waves at its boundaries, is employed to mimic the swimming microorganisms. We adopt various simulation parameters, including friction Reynolds number Re τ = 180, two squirmer volume fractions 𝜑 0 12.7 % and 2.54 blocking ratio (squirmer radius/half-channel...

Microorganisms or man-made microswimmers swimming near obstacles have been investigated intensively owing to their importance in biology, physiology, and biomedical engineering. In this work, a direct-forcing fictitious domain method is...

A parallel direct-forcing (DF) fictitious domain (FD) method for the simulation of particulate flows is reported in this paper. The computing strategies solution flow fields and particularly distributed Lagrange multiplier are presented, high efficiency code demonstrated. new then applied to study effects particle density (or inertia) on turbulent channel flow. results show that large-scale vortices weakened more severely, friction drag increases first reduces, as inertia increased.

We present a direct-forcing fictitious domain method for simulating non-Brownian squirmer particles with both the hydrodynamic interactions and collisions being fully resolved. In this method, we solve particle motion by distributing collocation points inside interior that overlay upon fixed Eulerian mesh. The fluid motions, including those of ``fictitious fluids'' extended into particle, are solved on entire computation domain. Pseudo-body forces used to enforce fluids follow movement. A...

A parallel direct-forcing fictitious domain method is employed to perform fully resolved numerical simulations of turbulent channel flow laden with finite-size particles. The effects the particle-fluid density ratio on turbulence modulation in are investigated at friction Reynolds number 180, particle volume fraction 0.84%, and ranging from 1 104.2. results show that variation drag not monotonic, a larger for 10.42, compared those unity significant reduction by particles observed large...

Interface-resolved direct numerical simulations of the particle-laden turbulent flows in a square duct are performed with direct-forcing fictitious domain method. The effects finite-size particles on mean and root-mean-square (RMS) velocities investigated at friction Reynolds number 150 (based velocity half width) particle volume fractions ranging from 0.78% to 7.07%. Our results show that secondary flow is enhanced its circulation center shifts closer cross section when added. reason for...

The influence of ambient fluid stratification on buoyant miscible jets and plumes is studied theoretically experimentally. Given a fixed set jet/plume parameters, an sandwiched between top bottom homogeneous densities, theoretical criterion identified to show how step-like density profiles constitute the most effective mixers within broad class stable transitions. This assessed both analytically experimentally, respectively by establishing rigorous priori estimates generalized...

A drag correlation is established for laminar particle-laden flows, based on data from the interfaced-resolved direct numerical simulations (IR-DNS) of particle sedimentation in a periodic domain at density ratio ranging 2 to 1000, concentration 0.59 % 14.16 %, and Reynolds number below 132. Our decreases slightly with increasing when other parameters are fixed. The then corrected account turbulence effect by introducing relative turbulent kinetic energy, IR-DNS upward channel flows laden...

Interface-resolved direct numerical simulations of downward particle-laden turbulent channel flows are performed by using a direct-forcing fictitious domain method. The effects the particle settling coefficient, density ratio (2, 10, and 100), size on fluid-turbulence interactions investigated at bulk Reynolds number 5746 volume fraction 2.36%. Our results indicate that significant particle-induced reduction in turbulence intensity does not take place for downflow low 2, generally increases...

A turbulent channel flow of a binary mixture finite-size neutrally buoyant ellipsoidal particles is studied by using parallel direct-forcing fictitious domain method at friction Reynolds number 180 and the particle aspect ratios 1/3 (oblate particle) 4 (prolate particle), respectively. The total volume fraction fixed 14.16% 21.24% relative prolate oblate are varied. mean velocity profile normalized bulk shows strong difference between single phase particulate flow, while showing small...

Correlations for the interfacial terms in fluid dissipation rate equation and Reynolds stress equations are established particle-laden flows, based on data from interfaced-resolved direct numerical simulations of particle sedimentation a periodic domain at density ratio ranging 0.01 to 1000, concentration 2.3 % 30.2 number below 250. The correlations mean drag pseudo-turbulent kinetic energy also reported, which used modelling term equation. obtained then incorporated model (RSM) (i.e....

In the present work, a three-dimensional fictitious domain method for particulate flows with heat transfer is proposed. For case of fixed particle temperature, an iterative scheme temperature Lagrange multiplier proposed, in order to determine its initial value and overcome spurious oscillation explicit at time stage different fluid temperatures. Both implicit schemes are proposed solution coupled solid equations freely evolving temperature. The suited large density ratios, specific or...