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NanoES Seminar
NanoES Seminar
WhenThursday, Jul 18, 2019, 12:30 – 1:30 p.m.
Campus roomNanaES 291
Event typesAcademics, Lectures/Seminars
Target AudienceEngineering students, faculty and alumni
Description

Title: Particle Adhesion and Detachment: a Historical Perspective

Gennady Ziskind, PhD
Professor of Mechanical Engineering, Ben-Gurion University of the Negev

Abstract:
The complexity of particle adhesion to and detachment from solid surfaces is caused by two inherent features: particle interaction with the surface to which it is attached, and particle interaction with the fluid to which it is exposed. The particle on the surface is held by a combination of physical attraction, chemical bonds and mechanical stresses, which is usually referred to as the adhesion force. Particle interaction with the fluid depends on the fluid properties and the flow regime. The two features cannot be separated: for example, fluid properties affect also the particle-surface interaction, while surface roughness may alter not only the particle-surface contact but also the fluid flow.

Extensive works on particle adhesion started to appear more than half a century ago. Eventually, it was realized that even when a perfectly spherical and smooth particle touches a nominally flat surface with no chemical activity, diffusive mixing or sintering, adhesion includes the particle and/or substrate deformation. The problem was difficult because possible deformations caused by surface forces had no sufficient explanation. Thus, the actual shape of bodies in contact and, as a result, the accurate magnitudes of surface forces between the particle and the substrate could not be calculated. In 1970s, two prominent models
of particle adhesion, JKR and DMT, appeared and started to be used in parallel, whereas in fact they were based on very different assumptions and starkly contradicted to one another.

It took about two decades to reconcile those models, but one should bear in mind that in any case they describe only the normal force necessary to separate between the bodies, while in the physical world the load may be tangential or oblique, creating a moment in addition to a force. In this talk, we are going to describe some historical milestones on the way to a better understanding of particle behavior on surfaces, including various attempts to model particle detachment, from more conventional force and moment balances to rather unorthodox energy accumulation concepts.

Bio:
Dr. Gennady Ziskind is Professor and Head of Department of Mechanical Engineering at Ben-Gurion University of the Negev in Beer-Sheva, Israel. He earned his M.Sc. and D.Sc. degrees from the Faculty of Mechanical Engineering at the Technion–Israel Institute of Technology, in the field of aerosol mechanics. His present research deals with various aspects of heat and mass transfer and multiphase systems, including phase-change energy storage and thermal management. He has co-authored more than 65 journal articles and more than 100 conference papers. Among other international activities, Dr. Ziskind serves as Associate Editor of Journal of Heat Transfer (ASME, re-appointed to the second term in 2018), and he has just assumed an AE position with International Journal of Thermal Sciences (Elsevier).

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