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2014 年 07 月 10 日
Seminar - "What is a Fluid and how do we model them?" By Prof. K R. Rajagopal

Date: 10 July 2014 (Thursday)

Time: 11:00 am – 12:00 pm

Venue:EF305, The Hong Kong Polytechnic University

Abstract:

This talk will include two parts. In the first part the development of innovative
methods for characterizing the mechanical properties of nanowires, nanobelts and
ultrathin films will be introduced. In the second part the fundamental understanding of
deformation mechanisms of a thin film multilayered structure under mechanical loading
and its removal characteristics involved in abrasive machining will be discussed.

Concepts such as fluids and solids are not as clear and unequivocal as their usage suggests; the concept of a fluid is very fluid and that of a solid not so solid! After a discussion of why most definitions that are used, from the most elementary definition that one encounters in a first course in physics, to sophisticated mathematical definitions based on symmetry groups, are totally inadequate, a rationale is presented for characterizing “fluid-like” and “solid-like” behavior. Then, several generalizations of the usual Navier-Stokes model that forms a cornerstone of fluid mechanics are discussed. Some views of the pioneers of fluid mechanics that have not been given the attention that they deserve are presented. Contrary to ideas that stem from the works of Bernoulli, D’Alembert and Lagrange which have unfortunately become entrenched in mechanics with regard to the determination of the “constraint response”, which do not allow for the possibility of the material moduli to depend on the Lagrange multiplier that enforces the constraint, an idea introduced by Gauss for describing the mechanics of rigid body is generalized so that it can be applied to deformable continua and its implications with regard to the modeling of fluids wherein the material moduli can depend on the Lagrange multiplier are discussed. Finally, some further generalizations to implicit constitutive theories are discussed.

Bio-sketch:

Prof. Rajagopal obtained his PhD in mechanics from University of Minnesota in 1978. He is now Regents Professor, University Distinguished Professor, Forsyth Chair Professor of mechanical engineering and Professor of Chemical Engineering, Civil Engineering, Biomedical Engineering and Mathematics at Texas A&M University. He is editor-in-chief for International Journal of Engineering Science and serves as editorial board member for various international journals. Prof. Rajagopal has published 8 books and 489 referred papers.

This talk will include two parts. In the first part the development of innovativemethods for characterizing the mechanical properties of nanowires, nanobelts andultrathin films will be introduced. In the second part the fundamental understanding ofdeformation mechanisms of a thin film multilayered structure under mechanical loadingand its removal characteristics involved in abrasive machining will be discussed.