Mechanics Colloquim
PROGRAM
PROGRAM ZA SEPTEMBAR 2015.
Pozivamo Vas da učestvujete u radu sednica Odeljenja i to:
Sreda, 2. septembar 2015. u 18 casova, sala 301f:
Javier Urzay, Center for Turbulence Research, Stanford University
(http://web.stanford.edu/~jurzay/)
RECENT ADVANCES AND OPEN CHALLENGES IN HIGH-SPEED COMBUSTION PHYSICS
Abstract: Great efforts have been dedicated over the last 50 years to the
research and development of high-speed aerospace vehicles for terrestrial
transportation, space exploration, and long-range global-strike weapons.
However, superlative challenges related to mixing and combustion were
identified very early in the history of development of high-speed
propulsion. This lecture will review recent advances in the understanding of
the fundamental physics and formulation of high-speed combustion, including
autoigniting fuel sprays and supersonic flames. The presentation will
emphasize the importance of interpreting dimensionless parameters in
canonical problems for enabling understanding of more complex physical
scenarios.
Petak, 4. septembar 2015. u 17 casova, Sala 301f MI SANU:
Kostas A.Lazopoulos, Mechanics Laboratory, School of Applied Maths &
Physics, National Technical University of Athens, Greece
FRACTIONAL CONTINUUM MECHANICS
Abstract: Since modern continuum mechanics is mainly characterized by the
strong influence of microstructure, Fractional Continuum Mechanics has been
a promising research field, satisfying both experimental and theoretical
demands. The geometry of the fractional differential is corrected and the
geometry of the tangent spaces of a manifold is clarified providing the
bases of the missing Fractional Differential Geometry. The Fractional
Vector
Calculus is revisited along with the basic field theorems of Green, Stokes
and Gauss. New concepts of the differential forms, such as fractional
gradient, divergence and rotation are introduced. Application of the
Fractional Vector Calculus to Continuum Mechanics is presented. The
Fractional right and left Cauchy-Green deformation tensors and Green
(Lagrange) and Euler-Almanssi strain tensors are exhibited. The change of
volume and the surface due to deformation (configuration change) of a
deformable body are also discussed. Fractional stress tensors are also
introduced. Further the Fractional Continuum Mechanics principles yielding
the fractional continuity and motion equations are also derived.
Sreda, 30. septembar 2015. u 18 casova, sala 301f, MI
SANU
Srdjan Kostic, naucni saradnik, Institut za vodoprivredu ,,Jaroslav Cerni'',
Beograd
srdjan.kostic@jcerni.co.rs, srdjanrgf@gmail.com
NELINEARNA DINAMIKA SEIZMOGENIH RASEDA
Rezime: Seizmogeni rasedi predstavljaju mehanicke diskontiuitete u Zemljinoj
kori, po kojima kretanje u odredjenom velicinskom podrucju nije zanemarljivo
i moze da uslovi nastanak zemljotresa. Sa stanovista teorijske mehanike,
seizmicko kretanje duz raseda pokazuje svojstva stik-slip pomeranja, odnosno
aperiodicnog smenjivanja ciklusa naglog, kratkotrajnog kretanja velike
amplitude i dugotrajnog stacionarnog stanja (pomeranja vrlo male amplitude).
Sa stanovista nelinearne dinamike, seizmicki rezim kretanja moze da se
objasni ili postojanjem stranog atraktora (deterministicki haos), ili
uticajem seizmickog suma. Na seminaru ce biti prikazani rezultati
dosadasnjeg rada autora na izucavanju dinamike osnovnih mehanickih modela
pomeranja duz seizmogenih raseda. Modeli su predstavljani nizom blokova koji
su medjusobno povezani elasticnim oprugama i krecu se po hrapavoj povrsi.
Dinamika ovih modela definisana je sistemima diferencijalnih jednacina sa
kasnjenjem i sa sumom, pri cemu je kontakt blokova i hrapave povrsi odredjen
specificnim zakonima trenja zavisnim samo od brzine pomeranja blokova ili i
od brzine blokova i od stanja hrapavosti povrsi po joj se blokovi krecu.
Resenja ovih sistema jednacina, za odredjene vrednosti kontrolnih
parametara, ukazuju na pojavu bifurkacija u dinamickom sistemu, sa tipovima
oscilacija koji mogu odgovarati razlicitim rezimima seizmickog i aseizmickog
kretanja. Rezultati istrazivanja ukazuju na to da broj pokrenuti blokova u
funkciji njihove amplitude pokazuje karakteristicnu Gutenberg-Rihter
raspodelu, koja je utvrdjena da vazi za distribuciju realno osmatranih
zemljotresa.
Predavanja su namenjena sirokom krugu slusalaca, ukljucujuci studente redovnih i doktorskih studija. Odrzavaju se sredom sa pocetkom u 18 casova u sali 301f na trecem spratu zgrade Matematickog instituta SANU, Knez Mihailova 36.