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ME-EM Virtual Graduate Seminar Speaker Series
Anubhab Roy, PhD
Indian Institute of Technology Madras
Abstract: Sedimentation of non-spherical particles occurs in many natural situations and has important consequences for a wide range of engineering applications. The orientation of non-spherical sedimenting particles influences the rate of sedimentation, the presence or absence of horizontal drift and the scattering of light from particle suspensions. Development of accurate models for the forces acting on fibres moving through fluids has long been a central problem in fluid mechanics. Stokes (1851) considered the drag on an infinite cylinder in the paper in which he introduced his viscous drag law, but it was not until 60 years later with the work of Oseen (1910) and Lamb (1911) that an accurate model was developed. Extensive efforts to observe and model forces on cylinders with finite length developed slowly until slender-body theory was formalized by Batchelor (1970) and Cox (1970).
In this talk I will discuss the effects of fluid inertia on the settling motion of fibers. The classical results of Khayat & Cox (1989) is used first to explain two experimental observations - a symmetry breaking orientational transition in sedimenting asymmetric fibers and the orientation distribution of symmetric fibers settling in a turbulent flow. The theory of Khayat & Cox uses a matched asymptotic expansion with a viscous inner flow and Oseen’s approximation for the outer flow. We develop a novel finite Re slender body theory that allows the inner flow to be described by steady Navier-Stokes and thus provide better comparisons to realistic scenarios where the Reynolds number (Re) defined based on the fiber diameter is non-zero.
Bio: Dr. Roy is an Assistant Professor in the Department of Applied Mechanics, Indian Institute of Technology Madras (IIT-M), Chennai, India. He received his PhD in Engineering Mechanics from Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru in 2013 and B. Tech degree in Civil Engineering from Indian Institute of Technology-BHU, Varanasi (IIT-BHU) in 2006. He was a postdoctoral fellow at the School of Chemical and Biomolecular Engineering, Cornell University before joining the Fluid Mechanics group at Applied Mechanics-IIT-M. His work focusses on hydrodynamic instabilities and suspension dynamics, with applications to geophysical flows. He is the recipient of Young Scientist Award (2020) from Indian National Science Academy and Young Faculty Recognition Award (2020) from IIT Madras.
Invited by: Susanta Ghosh
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