Spring 2016
Seminars are held on Mondays from 2:30 - 3:30PM in Cullimore Hall, Room 611, unless noted otherwise. For questions about the seminar schedule, please contact David Shirokoff.
Date: April 18, 2016
Speaker: Abhinendra Singh
Benjamin Levich Institute,
City University of New York
Title: "Effect of Cohesion on the Flow Behavior: From Dry Granular Matter to Suspensions"
Abstract:
Particulate systems (such as toothpaste, clay etc.) are omnipresent in our daily life. Computer simulations have turned out to be a powerful tool to investigate the flow behavior of such systems. A topic of special relevance is to understand the yield behavior of these materials, i.e., when do they start to flow or what is the stress required to keep them flowing? My talk will be divided into two sections: I will begin with talking about the interaction between two dry, fine cohesive particles, which are at the heart of all the complex many body problems. In order to understand the dissipative collision between two particles, the coefficient of normal restitution (COR) is the key element. Using the energy conservation arguments, we expressed the COR as a function of the impact velocity. I will show and rationalize that particles show a sticking behavior at low impact velocity, while they rebound at higher velocities [1]. Further, I will also present the effect of cohesion on the bulk behavior of slow, quasistatic flow behavior of granular materials. In order to quantify the intensity of cohesion, we introduce the “Bond number (Bo)”. And we found that Bo =1 acts as crossover point showing many features of slow granular flows to be independent of cohesion for Bo<1, while effect of cohesion shows up for Bo>1 [2]. The next part of the seminar will focus on the effect of cohesion on the flow behavior of concentrated suspensions. Here, I will present how the attraction affects the shear thickening in case of concentrated suspensions. One interesting observation, which was predicted previously but not simulated to date, is that attractive forces can result in a large lowshear viscosity (or yield stress) which obscures the shear thickening.
References:
[1] A. Singh, V. Magnanimo, and S. Luding, http://arxiv.org/abs/1503.03720
[2] A. Singh, V. Magnanimo, K. Saitoh, and S. Luding, Phys. Rev. E 90,
022202 (2014)