146 research outputs found
On the orientational dependence of drag experienced by spheroids
No full textThe flow around different prolate (needle-like) and oblate (disc-like) spheroids is studied using a multi-relaxation-time lattice Boltzmann method. We compute the mean drag coefficient CD,ϕ at different incident angles ϕ for a wide range of Reynolds numbers ( Re ). We show that the sine-squared drag law CD,ϕ=CD,ϕ=0∘+(CD,ϕ=90∘−CD,ϕ=0∘)sin2ϕ holds up to large Reynolds numbers, Re=2000 . Further, we explore the physical origin behind the sine-squared law, and reveal that, surprisingly, this does not occur due to linearity of flow fields. Instead, it occurs due to an interesting pattern of pressure distribution contributing to the drag at higher Re for different incident angles. The present results demonstrate that it is possible to perform just two simulations at ϕ=0∘ and ϕ=90∘ for a given Re and obtain particle-shape-specific CD at arbitrary incident angles. However, the model has limited applicability to flatter oblate spheroids, which do not exhibit the sine-squared interpolation, even for Re=100 , due to stronger wake-induced drag. Regarding lift coefficients, we find that the equivalent theoretical equation can provide a reasonable approximation, even at high Re , for prolate spheroids.Accepted Author ManuscriptIntensified Reaction and Separation System
Computer simulation of entanglements in viscoelastic polymer melts
No full textIn this thesis we report on computer simulations of polymer melts. Polymers in a melt can be viewed as long molecules which coil around each other and hinder each other’s motions: they are “entangled”. Entanglements occur because bonds between two adjacent atoms in a polymer chain can never be crossed by other such bonds. The goal of our study was to simulate and to understand the dynamical and rheological behavior resulting from this entanglement effect. Because of its relative simplicity, we have chosen polyethylene (PE) as our primary system of interest
CECAM workshop on Structure and rheology of self-assembling and aggregating colloidal suspensions : theory, simulation and experiment , October 12-14, 2005, Lyon, France
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Multiscale reaction kinetics in different flow regimes
No full textUnderstanding catalytic reactions for the production of cleaner gasolin
Experiments and modelling of non-spherical particle fluidization:an experimental and numerical study on the behaviour of spherocylindrical particles in pseudo-2D fluidized beds
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A convenient internal numbering-up strategy for the scale up of gas-liquid photoredox catalysis
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