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Seminar on Mechanical Science and Bioengineering
160th | Nov 29, 2019 15:00-16:00 Room A328 |
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| In Japanese | |
159th | Nov 13, 2019 16:30-17:30 Room D404 |
| Turbulent flow fields and their statistical proximity to null models using synthetic data | |
| The scientific questions we ask regarding the physics ofturbulence are typically investigates using experimental measurements (e.g. hot wires to obtain single-point, time-series data), or numerical simulations (fully time resolved data in time and three spatial dimensions) but with a cost in terms of data storage. In nonlinear physics, the use of synthetic, surrogate data has been important for testing the statistical significance of values measured from data (e.g. the maximal Lyapunov exponent of a system observed from a time series). In this talk I will outline this philosophy and then discuss in detail two contributions that can be used for examining turbulence with these methods. The first approach uses a complex-valued wavelet transform to permit turbulence data to be studied, conditioned on preservation of their multifractal structure. The second distinct method is based on the randomisation of the velocity gradient tensor rather than a specific scalar quantity. Some preliminary applications of these techniques will be described. | |
| Chris Keylock Loughborough University |
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158th | Nov 11, 2019 15:00-16:00 Room D404 |
| In Japanese | |
157th | Oct 1, 2019 14:00-15:30 Room G508 |
| Finite-size particle clustering in homogeneous-isotropic turbulence | |
| Although fluid-particle systems are technologically relevant in many contexts, our understanding of their dynamics is still incomplete. Phenomena such as particle clustering are therefore still difficult to predict with the aid of engineering-type approaches. The situation is even more intricate when the particles are not small compared to the smallest flow scales, and/or the Reynolds number on the particle scale is not negligibly small. In this situation it becomes necessary to resolve the flow around the individual particles up to a precision which yields the correct hydrodynamic forces. This fully-resolved approach, although computationally demanding, is becoming increasingly feasible for investigating said dynamics in idealized configurations. Here we will report on numerical studies of forced homogeneous-isotropic turbulence seeded with spherical particles having diameters ranging from 5 to 17 Kolmogorov length scales, in particular without gravity. We are interested in elucidating the turbulence/particle interaction mechanisms by investigating such questions as: in which parameter regime does particle clustering arise? How does its intensity scale? Where are particles preferentially located with respect to turbulent flow structures? | |
| Prof. Markus Uhlmann Karlsruher Institut für Technologie | |
156th | Sep 9, 2019 16:00-17:00 Room D404 |
| Nonlinear wave like coherent structures in non-parallel flows | |
| High-speed boundary layer and jet flows are typical flows having a self-similar laminar profile at sufficiently large Reynolds numbers. Here we shall consider development of nonlinear wave-like coherent structures on top of those non-parallel flows. In the past 30 years, numerous wave-like invariant solutions were found in parallel shear flows, as this is the first step in applying the dynamical systems theory picture of turbulence to the flows. However, for inherently non-parallel flows, the slow spatial development of the base flow causes difficulties in applying similar numerical computational methodology. Here we use various reductions of the governing equations based on the large Reynolds number multiple scale analysis, in order to compute (quasi) invariant solutions embedded in a local station of non-parallel flows. | |
| Dr. Kengo Deguchi School of Mathematical Sciences, Monash University | |
155th | July 12, 2019 10:30-11:30 Seminar room, Engineering Science International Building |
| Microfluidic applications for Assisted Reproductive Technology (ART) | |
| Many biological studies, drug screening methods, and cellular therapies require preservation, culture, and manipulation of living cells outside their natural environment. The gap between the cellular microenvironment in vivo and in vitro and non-physiological preservation conditions such as low temperatures and cryoprotectant toxicity, however, pose challenges for obtaining physiologically relevant responses from cells used in basic biological studies or drug screenings and for achieving the maximum functional potential from cells used therapeutically. The micro- and nano- technologies and methods close the physiological gap to provide biological information otherwise unobtainable and enhance cellular performance in therapeutic applications. This talk will present multidisciplinary efforts directed towards the development of biomedical micro- and nano systems inspired by the human body and biophysics. Specifically, this talk will deal with i) A microfluidic system that improves in vitro fertilization (IVF) technology by recreating spatio-temporal patterns of chemical and fluid mechanical environments that cells may experience in the body, ii) Microfluidic systems for single cell analysis: embryo metabolism and controlled cryoprotectant loading profiles, iii) Microcapillary heat and mass transfer system for “ice-free” cryopreservation (or vitrification) of cells. | |
| Associate Prof. Yun Seok Heo Biomedical Engineering, School of Medicine, Keimyung University, Korea | |
154th | July 1, 2019 14:00-15:30 Seminar room, Engineering Science International Building |
| In Japanese | |
153rd | Jun 27, 2019 10:40-11:30 Room C419 (4th floor) |
| In Japanese | |
152nd | May 14, 2019 10:30-11:30 Seminar room, Engineering Science International Building |
| In Japanese | |
151st | May 7, 2019 15:30-17:10 Seminar room, Engineering Science International Building |
| Cellular Active Fluids | |
| Monolayers of cells in tissue and bacterial colonies growing on substrates are ample examples of materials that are continuously driven out of equilibrium by the activity of their constituent elements. One generic property of these active materials is the spontaneous emergence of collective flows which often leads to chaotic flow patterns characterised by swirls, jets, and topological defects in their orientation field. In this talk I will discuss recent works on cell monolayers and growing bacterial colonies, where we find interesting correlations between liquid crystal-like features of these active systems and their biological functionality. | |
| Amin Doostmohammadi Rudolf Peierls Centre for Theoretical Physics, University of Oxford, UK | |
| Mechanobiology of self-assembly and differentiation by stem cells under restricted adhesion condition | |
| Stem cells, including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) possess unlimited ability to expand under culture, and to differentiate into virtually all human cell types, making them invaluable biological resources with enormous application potential in medicine, basic studies and drug development. This talk will highlight our ongoing work aimed at understanding the mechanobiology of self-assembly and differentiation of stem cells in which we employ microfabrication techniques to modulate the stem cell culture microenvironment so as to unlock their differentiation and self-organization potentials. Specifically, we will introduce our original technique, namely, the micromesh technique, which enables us to modulate the balance between cell-cell and cell-substrate adhesions in order to influence tissue mechanics resulting from self-organization and differentiation of stem cells. We will demonstrate the potential of this approach to mechanically trigger trophoblast-like differentiation and primordial germ cell-like differentiation patterns in human iPSCs and murine ESCs, respectively. | |
| Kennedy Omondi Okeyo Institute for Frontier Life and Medical Sciences, Kyoto University |
