The near-wall streaks and the associated quasi-streamwise vortices are strongly reduced near a highly elastic wall while the flow becomes more correlated in the spanwise direction, similarly to what happens for flows over rough and porous walls. The turbulent flow in the channel is affected by the moving wall even at low values of elasticity since non-zero fluctuations of vertical velocity at the interface influence the flow dynamics.
#Particle playground values revert skin#
We show that the skin friction increases monotonically with the material elastic modulus. The simulations are carried out at Reynolds bulk $Re=2800$ and examine the effect of different elasticity and viscosity of the deformable wall. The multiphase flow is solved with a one-continuum formulation, using a monolithic velocity field for both the fluid and solid phase, which allows the use of a fully Eulerian formulation. In the fluid region the flow is governed by the incompressible Navier-Stokes (NS) equations, while the solid is a neo-Hookean material satisfying the incompressible Mooney-Rivlin law. We perform numerical simulations of a turbulent channel flow over an hyper-elastic wall. The total stress budgets reveals that the particle-induced stress contribution increases with the volume fraction $\Phi$ and decreases with deformability. In addition, we show that the normal stress differences exhibit a non-linear behavior, with a similar trend as in polymer and filament suspensions. We study the rheology of the visco-elastic suspension in plane Couette flow in the limit of vanishing inertia and examine the dependency of the effective viscosity $\mu$ on the solid volume-fraction $\Phi$, the capillary number $\mbox$ and demonstrate it also applies to data in literature for suspensions of capsules and red-blood cells. We consider suspensions of deformable particles in a Newtonian fluid by means of fully Eulerian numerical simulations with a one-continuum formulation. The experimental observations are in good agreement with the performed numerical simulations and provide insights into the dynamics of bubbles in laminar flows which can be utilized in the design of flow based multiphase flow reactors. One important outcome of this study is that the equilibrium position of bubbles in rectangular channels is different from that of solid particles. Moreover, in the shallow channels, having aspect ratios higher than one, the bubble moves towards the narrower sidewalls. For instance, at high Re, the flow pushes the bubble towards the wall while large Ca or moves the bubble towards the center. We find that the Reynolds number (Re), the capillary number (Ca), the diameter of the bubble (), and the aspect ratio of the channel are the influential parameters in this phenomenon. A T-junction geometry is employed to introduce bubbles into a microchannel and analyze their lateral equilibrium position in a range of Reynolds (1 < Re < 40) and capillary numbers (0.1 < Ca < 1). In this paper, we show that the trajectory of bubbles flowing in rectangular and square microchannels can be controlled by tuning the balance of forces acting on them. Deformable entities such as bubbles and droplets are considered in fewer studies despite their importance in multiphase microflows. Until now, the majority of the studies have focused on the behavior of rigid particles in order to provide guidelines for microfluidic applications such as sorting and filtering. Inertial microfluidics is an active field of research that deals with crossflow positioning of the suspended entities in microflows.
Finally, we explain the particle migration by computing the total force acting on the particle and its different components, viscous and elastic. Our simulations show that the results are not affected by the particle initial conditions, position and velocity. the particle is more deformable), with the particle reaching the final equilibrium position at the centerline in shorter times. We note that the migration dynamics and the final equilibrium position are almost independent of the Reynolds number, while they strongly depend on the particle elasticity in particular, the migration is faster as the elasticity increases (i.e. We observe that the particle deforms and undergoes a lateral displacement while traveling downstream through the pipe, finally focusing at the pipe centerline.
#Particle playground values revert full#
We study the full particle migration and deformation for different Reynolds numbers and for various levels of particle elasticity, to disentangle the interplay of inertia and elasticity on the particle focusing. We perform fully Eulerian numerical simulations of an initially spherical hyperelastic particle suspended in a Newtonian pressure-driven flow in a cylindrical straight pipe.
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