Fluids, ; Yu et al. Fluids, ; Lashgari et al. PRL, In this work, we use particleresolved numerical simulations to understand the effect of finite sized particles on wall-bounded pressure-driven or plane Couette turbulent flows, slightly above the laminar-turbulent transition limit.
We find that in turbulent Couette flow, wall-normal profiles of the flow velocity and Reynolds stress components reveal that there is no significant difference between single phase and two-phase flows at equivalent effective Reynolds number, except that the wall shear stress is higher for the two-phase flow.
However temporal and modal analysis of flow fluctuations, suggest that besides increasing small scale perturbation due to their rigidity, particles have an effect on the regeneration cycle of turbulence streak formation, streak breakdown and streamwise vortex regeneration.
Indeed, the shape of the streaks and the intermittent character of the flow amplitude and period of oscillation of the modal fluctuation energy are all altered by the particle presence, and especially by the inertial particles Wang et al. Fluid, When the particle shape deviates from sphericity spheroids with aspect ratios ranging between 0.
The transfer of particles between different coherent structures along the regeneration cycle period is analyzed at the end of the thesis.
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On the experimental side, we are foremost interested in the enhancement of water droplet collision-coalescence due to turbulent flow. Currently, it is theorized that in order to have rain from warm clouds where ice particle are limited in number , small water droplets of size 10 to 20 microns must collide and coalesce to form rain droplets of roughly milimeter size.
Particles in Turbulent Flows | Wiley Online Books
It is hard to imagine that these collision can take place without the help of external forcing from turbulence flow, which common experience as aircraft passenger tells us is plentiful in clouds e. The puzzle of whether this theory is correct and to which extend, requires careful experimental studies. To that end, we will generated turbulent flow and water droplets in laborotary, each requires careful and creative design.
We will use Particle Tracking Velocimetry, a modern technique of observing 3-D particle trajectories, to observe droplet behaviour and collisions. These time scales are scaled by a large eddy turnover time of the flow T eddy. Bottom panel: Contributions to the irreversibility parameter Ir from vortical red and strain-dominated blue regions of the flow.
Particles Turbulence Flow
Left panel: The PDFs of the x component of the velocity of the particle. The black solid line shows a normal distribution with mean zero and standard deviation unity. Right panel: The autocorrelation function C v x of the x component of the velocity of the particle.
E 97 , — Published 2 March Abstract We present an extensive numerical study of the time irreversibility of the dynamics of heavy inertial particles in three-dimensional, statistically homogeneous, and isotropic turbulent flows. Research Areas.
Particle-laden flows Turbulence. Issue Vol. Authorization Required.
Related Particles in turbulent flows
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