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Seminar on Mechanical Science and Bioengineering
100th | June 25, 2015 10:30-11:30 A304 |
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| Quantifiaction of clinical treatments for the biomechanical research | |
| Surgeons applies various translational and rotational loads for diagnosis
and surgeries. The loads applied for diagnosis arepassive palpations, pushing
or pulling loads for measuring joint stability, pain, varus/valgus stress tests.
The loads applied during intraoperative surgeries includes ligament tensioning
for joint soft tissue balancing, compression for anatomic reduction of fracture
bones, cable tightening for fracture fixation, suture pulling for arthroscopic
anchor implantation etc. However, the clinical treatment are still intuitive
and experience-based. Biomechanists want to assess the clinical phenomena
quantitatively rather than qualitatively. Here we can ask surgeons the next
questions： Q1. Do you apply palpation load reproducibly? Is your diagnosis objective or fair intrasubjectively or intersubjectively? Q2. Do you apply surgical ligament stretching or fixation force in reproducible or reasonable manner? How can you be sure that you are doing right? Ca you give beginning surgeons the amount of the loads? Q3. How much pulling or push forces should we apply in practical biomechanical tests of newly developed joint prosthesis, fixation devices or suture anchors? Are the FDA and CE medical device certification protocols practical? In this regard, this speak will share quantification and standardization of clinical treatments for biomechanics research. | |
| Prof. Yeon Soo Lee Dept. of Biomedical Engineering, College of Medical Health Science, Catholic University of Daegu | |
99th | May 20, 2015 14:00-15:30 Seminar Room D |
| Cavitation issues in hydraulic turbine and pump-turbines | |
| Hydraulic turbines and pump-turbines for hydropower stations Cavitation in storage pumps and pump-turbine Cavitation in axial turbines Cavitation in Francis turbine Turbine dynamic behavior | |
| Prof. Francois Avellan Ecole polytechnique federale de Lausanne | |
98th | Mar 13, 2015 14:00-15:30 Room B104 |
| On the continuation of (relative) periodic orbits in box turbulence | |
| In this informal presentation, I will discuss the technicalities of the continuation of periodic orbits in dissipative PDEs with symmetries. I will illustrate the continuation algorithm with examples in the direct numerical simulation and large eddy simulation of fluid motion in a triply periodic domain. | |
| Prof. Lennaert van Veen Faculty of Science, University of Ontario Institute of Technology | |
97th | Feb 13, 2015 14:30-15:30 Room B103 |
| (1) Exact coherent states in plane Poiseuille flow (2) Homotopy between plane Couette flow and pipe flow | |
| (1) Two new families of travelling wave solutions are found in plane Poiseuille flow by continuing the stationary and travelling mirror-symmetric exact coherent states in plane Couette flow. One of them, referred to as MS hereafter, arises from a saddle-node bifurcation, characterised by inherited mirror-symmetry in the spanwise direction. The second family, referred to as AS hereafter, bifurcates by breaking the mid-plane symmetry of MS. Both MS and AS are characterised by two quasi-streamwise low-speed streaks within one spanwise period. The low-speed streaks are aligned with the vertical planes of mirror-symmetry, with their width varying in a varicose fashion in the streamwise direction. These streaks appear close to both top and bottom channel walls for MS, and to only one of the channel walls for AS. We find that the Reynolds numbers at the saddle-node bifurcation for MS and AS are smaller than that of the exact coherent state in plane Poiseuille flow known to date (Waleffe 2003). (2) In order to investigate symmetry connections between two canonical shear flows, i.e. plane Couette (PCF) and pipe flow (PF), which are linearly stable for all Reynolds numbers and therefore undergo subcritical transition, we take annular Poiseuille-Couette flow (APCF) as an intermediary Although PCF and PF are very different geometrically, APCF recovers PCF by taking the narrow gap limit and also PF by taking the limit of vanishing inner cylinder where a homotopy of the basis functions from no-slip to regular conditions at the centre is considered. We show that the double-layered mirror-symmetric solutions in sliding Couette flow (APCF without axial pressure gradient) found by Deguchi & Nagata (2011) can be traced back to the mirror-symmetric solutions in PCF. Also we show that only the double-layered solution successfully reaches the PF limit reproducing the mirror-symmetric solution in PF classified as M1 by Pringle & Kerswell (2007). Symmetry connections for invariant sets between plane Couette flow and plane Poiseuille flow has been presented in my first talk (1). The mirror-symmetric structures existing in shear flows in common may play a robust role in subcritical transition to turbulence. | |
| Prof. Masato Nagata Professor, Department of Mechanics, Tianjin University (P.R. China) | |
96th | Jan 15, 2015 15:00-16:30 Seminar Room J |
| Localised turbulence in circular pipe with gradual expansion: experiments and simulations | |
| Transition to turbulence in pipe flow has been described as an outstanding challenge in hydrodynamics stability theory since theoretical work suggests the flow is linearly stable. Yet, todays powerful computers are able to reproduce many of its properties. However, in the real world, pipe flow is rarely uniform. In this seminar, the results of a combined experimental and three-dimensional direct numerical simulations of Navier-Stokes equations for incompressible viscous fluid in a diverging circular pipe will be presented. Initially, at low Reynolds number, the solution is steady. As the Reynolds number is increased, a symmetry-breaking bifurcation occurs, where an asymmetry growth in the recirculation state is observed. Further increment in velocity leads to the transition of the flow from laminar to localised turbulent state by formation of disordered time-dependent turbulent patch downstream the divergent section. The transition and relaminarization experiments described here quantify the lifetime and the extent of turbulence. The findings suggest that the transition scenario in slowly diverging pipes is a combination of stages similar to those observed in sudden expansions and in straight circular pipe flow. | |
| Dr. Jorge Peixinho CNRS et Universite du Havre | |
95th | Sep. 8, 2014 (Seminar 1) 10:30-12:00 (Seminar 2) 13:00-14:30 Lecture Room B205 |
| See Japanese Page | |
| Prof. Kenichiro Takeishi Faculty of Science and Engineering, Tokushima Bunri University | |
94th | June 13, 2014 13:00-14:00 Seminar Room J |
| See Japanese Page | |
| Prof. Kensuke Kageyama Graduate School of Science and Engineering, Saitama University | |
93rd | May 20, 2014 16:00-17:30 Seminar Room C419-423 |
| Experimental study and basic modeling of simple thermoacoustic oscillators | |
| This seminar deals with the study of self-sustained thermoacoustic oscillations induced by boundary layer effects within a porous material (referred to as a ≪ stack ≫) submitted to a temperature gradient. This process of generation of (acoustic) work from heat has been studied for about three decades, notably because it can be advantageously applied to the development of new kinds of thermodynamic engines. After a brief introduction to thermoacoustic phenomena, I will provide an overview of the different processes saturating wave amplitude growth in thermoacoustic oscillators (acoustic streaming, entrance effects, nonlinear propagation...) and try to emphasize that, despite of the active research in the field, those processes are still poorly described. This will be notably shown from the experimental study (notably using Digital Holography) of a simple oscillator called the thermoacoustic laser. The remaining part of the talk will be devoted the forcing of thermoacoustic oscillators by external sound sources: universal aspects of synchronization phenomena will be emphasized from the experimental study of the thermoacoustic laser coupled to a loudspeaker, and the interest in forcing thermoacoustic oscillations to increase an engine's efficiency will be also demonstrated. | |
| Dr. Guillaume PENELET Laboratoire d'Acoustique de l'Universite du Maine MR CNRS 6613, Avenue Olivier Messiaen, 72085 Le Mans cedex 9, France | |
92nd | April 25, 2014 10:30-11:30 Seminar Room C419-423 |
| Cellular solids studied by X-ray tomography and finite element modelling - a review | |
| This lecture reviews the use of X-ray Computed Tomography (XRCT) to investigate the cellular solids' structure and properties. In the first part, the possibilities offered by XRCT are exposed. Some examples of tomographic images are shown for the three classes of materials (polymer, ceramic and metal based). Different characterisation of the cellular solids performed thanks to XRCT images are explained: calculation of morphological parameters, in-situ and ex-situ mechanical tests. It is shown that the tomographic images are often used in the literature to perform finite element modeling. The second part presents the existing methods to create the meshes from the tomographic images. Some interesting results from the finite element simulations are highlighted. | |
| Eric Maire INSA de Lyon, France | |
91st | April 17, 2014 15:00-16:30 Seminar Room D404-408 |
| Vortical structures in homogeneous high Reynolds number turbulence | |
| DNS data analysis of incompressible homogeneous forced turbulence with the Taylor micro-scale Reynolds number up to O(1000) shows that the vortical structures in high Reynolds number (Re) turbulence are qualitatively different from those in low Reynolds number turbulence. In high Re turbulence, elongated strong vortices are reasonably close packed and dense in layer-like regions with thickness of the order of the Taylor micro-scale and with length of the order of the integral length scale. Conditional statistics near the layer-like regions will be discussed. | |
| Dr. Takashi Ishihara, Assistant Professor Center for Computational Science, Graduate School of Engineering, Nagoya University |
