519 research outputs found
Secondary vortices in swirling flow
Twisted tapes are used to induce swirling flow and improve mixing. The flow
induced by a 180 degree twisted tape with length (pitch) 60 mm and diameter
25.4 mm in a circular pipe was investigated using Laser Doppler Velocimetry
(LDV) measurements. Tangential velocity profiles downstream of the twisted tape
swirler were measured at multiple locations along the pipe axis, across the
horizontal diameter of the pipe. The profiles showed an unexpected transition
along the pipe axis from regular swirling flow to an apparent counter-rotation
near the pipe axis, and then reverting back to regular swirling flow. Injecting
fine air bubbles into the flow showed the existence of two co-rotating helical
vortices superimposed over the main swirling flow. The close proximity of the
two co-rotating vortices creates the local reversing flow at the pipe
centerline. The secondary vortices are analyzed with high speed camera videos
and numerical simulations.Comment: 2 videos include
Liquid-gas-solid flows with lattice Boltzmann: Simulation of floating bodies
This paper presents a model for the simulation of liquid-gas-solid flows by
means of the lattice Boltzmann method. The approach is built upon previous
works for the simulation of liquid-solid particle suspensions on the one hand,
and on a liquid-gas free surface model on the other. We show how the two
approaches can be unified by a novel set of dynamic cell conversion rules. For
evaluation, we concentrate on the rotational stability of non-spherical rigid
bodies floating on a plane water surface - a classical hydrostatic problem
known from naval architecture. We show the consistency of our method in this
kind of flows and obtain convergence towards the ideal solution for the
measured heeling stability of a floating box.Comment: 22 pages, Preprint submitted to Computers and Mathematics with
Applications Special Issue ICMMES 2011, Proceedings of the Eighth
International Conference for Mesoscopic Methods in Engineering and Scienc
Graphs of gonality three
In 2013, Chan classified all metric hyperelliptic graphs, proving that
divisorial gonality and geometric gonality are equivalent in the hyperelliptic
case. We show that such a classification extends to combinatorial graphs of
divisorial gonality three, under certain edge- and vertex-connectivity
assumptions. We also give a construction for graphs of divisorial gonality
three, and provide conditions for determining when a graph is not of divisorial
gonality three.Comment: 19 pages, 13 figures; corrected statements of Theorems 1.2 and 4.1,
as well as material in Section
Cellular Blood Flow
The fluid dynamics video that is presented here outlines recent advances in
the simulation of multiphase cellular blood flow through the direct numerical
simulations of deformable red blood cells (RBCs) demonstrated through several
numerical experiments. Videos show particle deformation, shear stress on the
particle surface, and the formation of particle clusters in both
Hagen-Poiseuille and shear flow.Comment: 2 pages, one hyperlink to 2 video
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