334 research outputs found
Vortex Dynamics in The Transitional and Turbulent Wake of 6:1 Prolate Spheroid at 45-deg incidence angle
No full textThe incompressible flow past a 6:1 prolate spheroid with an inclination angle of 45o at Re = 3,000 has been studied by means of direct numerical simulations (DNS). The Reynolds number is based on the inflow velocity and minor-axis length. The preliminary results presented here are focused mainly on vortex dynamics and vortical structures in the wake. The wake behind this configuration starts almost symmetric but is soon strongly deflected and bent as it evolves to the intermediate wake. A pair of unequal-strength vortices dominates the intermediate wake, of which one exhibits the shape of a long vortex tube while the other rapidly breaks down into turbulent-like vortical structures
Dynamics of inertial disk particles in turbulent channel flow
No full textA suspension of oblate spheroidal (disk-like) particles in turbulent channel flow has been investigated with focus on the translational and rotational particle statistics. The effects of particle aspect ratio and inertia have been explored. The disk-like particles exhibited a significant preferential orientation in the plane of the mean shear. The influence of the particle shape on the orientation and rotation diminished as translational inertia increased from Stokes number 1 to 30. Isotropization of both orientation and rotation could be observed in the core region of the channel. Keywords: oblate spheroids, preferential orientation, shape effects, inertia effects
The effect of turbulence on particle impaction om a cylinder in a cross flow
No full textParticle impaction on a cylinder in a cross flow is investigated with the use of Direct Numerical Simulations (DNS), with a focus on the effect of turbulence on the impaction efficiency. It is found that for particles with Stokes numbers in the boundary stopping mode there is up to ten times more front side impaction for turbulence with a large integral scale, than for a corresponding laminar flow. The back side impaction efficiency is also found to be influenced by the turbulence. The highest back side impaction efficiency is found for turbulence with small integral scales
Inertial effects on non-spherical particle rotation on turbulent channel flow
No full textWe investigated the rotation of non-spherical particles (rod-like and disk-like) in turbulent channel flow with focus on inertial effects. A direct numerical simulation (DNS) with an Eulerian-Lagrangian approach was performed. A wide range of particle aspect ratios, λ, ranging from 0.01 to 50 were considered for Stokes numbers St equal to 1 and 30. In the particle reference frame, statistical results reveal the importance of shape effect on the particle rotation. The rods (λ > 1) are spinning (rotation about their symmetry axis) more than tumbling (rotation about other axes) whereas disks (λ < 1) behave oppositely. With increasing particle inertia, i.e. higher St, the preferential tumbling of the disks and the spinning of the rods are reduced. We ascribe these observations to the varying degree of alignment of the particle symmetry axis with the fluid vorticity vector
Bijdrage tot de kennis van vervaardiging, eigenschappen en verwerking der acetaatzijde
No full textApplied Science
Viskositeit en andere physische constanten in afhankelijkheid van temperatuur en chemische structuur: Onderzoek van minerale oliën, siliconen en enkele andere technisch belangrijke producten
No full textApplied Science
De verwijdering van organische stoffen uit oppervlaktewater, in het bijzonder uit veenwater, in Nederlandsch-Indië
No full textApplied Science
- …
