Finite-length effects on dynamical behavior of rod-like particles in wall-bounded turbulent flow
2015 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 76, 13-21 p.Article in journal (Refereed) Published
Combined Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) measurements have been performed in dilute suspensions of rod-like particles in wall turbulence. PIV results for the turbulence field in the water table flow apparatus compared favorably with data from Direct Numerical Simulations (DNS) of channel flow turbulence and the universality of near-wall turbulence justified comparisons with DNS of fiber-laden channel flow. In order to examine any shape effects on the dynamical behavior of elongated particles in wall-bounded turbulent flow, fibers with three different lengths but the same diameter were used. In the logarithmic part of the wall-layer, the translational fiber velocity was practically unaffected by the fiber length l. In the buffer layer, however, the fiber dynamics turned out to be severely constrained by the distance z to the wall. The short fibers accumulated preferentially in low-speed areas and adhered to the local fluid speed. The longer fibers (l/z > 1) exhibited a bi-modal probability distribution for the fiber velocity, which reflected an almost equal likelihood for a long fiber to reside in an ejection or in a sweep. It was also observed that in the buffer region, high-speed long fibers were almost randomly oriented whereas for all size cases the slowly moving fibers preferentially oriented in the streamwise direction. These phenomena have not been observed in DNS studies of fiber suspension flows and suggested l/z to be an essential parameter in a new generation of wall-collision models to be used in numerical studies.
Place, publisher, year, edition, pages
2015. Vol. 76, 13-21 p.
Dispersed multiphase flow, Fiber suspension, Fiber tracking, Particle Image Velocimetry (PIV), Particle Tracking Velocimetry (PTV), Turbulence, Channel flow, Dynamics, Fibers, Flow visualization, Groundwater, Probability distributions, Turbulent flow, Velocimeters, Velocity measurement, Wall flow, Fiber suspension flow, Fiber suspensions, Finite length effects, Particle image velocimetries, Particle tracking velocimetry, Streamwise directions, Wall-bounded turbulent flows, Suspensions (fluids)
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-174986DOI: 10.1016/j.ijmultiphaseflow.2015.05.015ISI: 000362050100002ScopusID: 2-s2.0-84938509205OAI: oai:DiVA.org:kth-174986DiVA: diva2:875189
QC 201511302015-11-302015-10-092015-11-30Bibliographically approved