1pm Tuesday 22 May
Venue: QB 1.15
Speaker: David Nicholson
Lunch will be provided in the Pugsley LT foyer area from 1pm.
Multi-agent data fusion systems provide a decentralised framework for enabling situation awareness and coordinated decision-making in uncertain, partially observed, and hazardous environments. Such environments are characteristic of a range of industrial applications, e.g. defence, disaster response. BAE Systems and EPSRC funded the Autonomous Learning Agents for Decentralised Data and Information Networks (ALADDIN) project from 2005-2010. This talk will present a number of examples of how fundamental multi-agent systems research, developed in ALADDIN, was matured and transferred into applications of interest to BAE Systems. The talk will then move on to describe ORCHID, a new project that builds on ALADDIN by introducing the human dimension to consider human-agent collectives. Applications of ORCHID Technology in future energy and disaster response systems will be presented.
1pm Tuesday 31st January
Venue: QB 1.15
Speaker: Dr John Macdonald
Abstract:
"The London Millennium Bridge infamously wobbled excessively on its opening day, but similar pedestrian-induced vibrations have since been identified on bridges of various structural forms. The mechanism has generally been attributed to synchronisation of pedestrian footsteps, but other site measurements, including on the Clifton Suspension Bridge, challenge this view. In contrast to other models of the behaviour, the approach taken considers the basic mechanism of human balance. This gives the surprising result that pedestrians walking randomly, as normal, can lead to dynamic instability, as observed on the Millennium Bridge. Ongoing developments in this area include further modelling of human gait and experiments on an oscillating treadmill with a motion capture system and a virtual reality representation of a bridge. It is hoped to address fundamental questions about human gait and balance, with potential applications to healthcare and robotics, as well as giving improved guidelines for bridge design."
1pm Tuesday 6 December
Venue: QB 1.15
Speaker: Andrea Cammarano
Despite the combined improvements in computing power and modelling capabilities one major hindrance to optimal design is the present incapability to capture experimentally (identify) nonlinear dynamic behaviour which characterise many engineering structures. Currently, it is standard engineering practice to apply techniques that can provide an answer to whether or not the system being tested is nonlinear but do not help to identify the type and magnitude of nonlinearity.
This work tries to investigate the complex mechanism behind the behaviour of non-linear structures with multi degrees of freedom. The main idea is to study where and why the usual methods cannot be used, and to develop new techniques to identify the source of the non-linearity and its effect on
the behaviour of the entire structure.
The final aim is to recreate a mathematical model able to reproduce and predict the behaviour of a structure, even in those cases where experimental data are not available.
Date: Tuesday 8 November
Time: 1pm
Venue: QB 1.15
Dr Andrea Diambra
Mixing soils with tensile resistant fibres is a new technique to improve strength and deformation characteristic of weak soils. However, despite the promising laboratory results, this technique has been currently applied only to marginal geotechnical structures. This talk will emphasise the advantages of using fibres and it will open the discussion for potential and more important civil engineering applications. It will be shown that addition of fibres may even prevent the soil liquefaction induced by earthquakes or dynamic actions.
Date: 17 June 2011
Room: 1.15 QB
Time: 2pm
Bob Randall is a visiting Emeritus Professor in the School of Mechanical and Manufacturing Engineering at the University of New South Wales (UNSW), Sydney, Australia, which he joined as a Senior Lecturer in 1988. Prior to that, he worked for the Danish company Bruel & Kjaer for 17 years, after ten years experience in the chemical and rubber industries in Australia, Canada and Sweden. He was promoted to Associate Professor in 1996 and to Professor in 2001. He has degrees in Mechanical Engineering and Arts (Mathematics, Swedish) from the Universities of Adelaide and Melbourne, respectively. He is the invited author of chapters on vibration measurement and analysis in a number of handbooks and encyclopedias, and a member of the editorial boards of four journals including Mechanical Systems and Signal Processing and Trans. IMechE Part C. His book Vibration-based Condition Monitoring was recently published by Wiley. He is the author of more than 190 papers in the fields of vibration analysis and machine diagnostics, and has successfully supervised fourteen PhD and three Masters projects in those areas. Since 1996, he has been Director of the DSTO (Defence Science and Technology Organisation) Centre of Expertise in Helicopter Structures and Diagnostics at UNSW.
In a number of fields, including machine condition monitoring (MCM) and operational modal analysis (OMA), one only has access to response measurements, which are a compound of forcing function and transfer function components. In the former case, it is of interest to divide the signal between the two components, since a change in condition could be indicated by either. In the latter case, it is the structural properties, as represented by the transfer functions, which are of interest. A first division is often into discrete frequency and random components, and a number of techniques have been devised to achieve this, with different pros and cons. Removal of discrete frequency components from stationary random responses, for example, makes it much easier to apply a number of OMA techniques. The paper compares a number of separation algorithms, including a couple of new ones based on the cepstrum. These have particular advantages when the “periodic” components are not completely periodic, such as blade pass frequencies in fans, turbines etc, where the transmission of periodic pulses to the casing is via a turbulent fluid, giving cyclostationary signals. The cepstrum itself provides a viable technique for operational modal analysis, at least for SIMO systems, where the forcing function and transfer function effects are additive in the cepstrum, and often separable. MIMO systems can be decomposed into a sum of SIMOs by a number of techniques involving blind source separation, and a number of possibilities are briefly discussed.
19th May 2011,
2.00 pm
Room 1.7 , Queen's Building
In the past few years, a technological revolution has occurred in the fields of integrated Micro Electro Mechanical Systems (MEMS) that offers new opportunities for smart structures design and optimization. We know today that the mechanical integration of active smart materials, electronics, chip sets and power supply systems is possible for the next generation of smart "composite" structures that can be considered as a new class of adaptive metamaterials. By using such an integrated active or hybrid distributed set of electromechanical transducers, one can attain new desired functionalities. In this sense, one can speak of "integrated distributed smart structures". In this work, we present an application of the Floquet-Bloch theorem in the context of electrodynamics for vibroacoustique power flow optimization by mean of distributed and shunted piezoelectric material. The main purpose of this work is first to propose a dedicated numerical approach able to compute the multi-modal wave dispersions curves into the whole first Brillouin zone for periodically distributed damped 2D mechanical systems. By using a specific indicator evaluating the evanescent part Bloch's waves, we optimize, in a second time, the piezoelectric shunting electrical impedance for controlling energy diffusion into the proposed semi-active distributed set of cells
4 April 2011, 2 pm
Venue: Room 1.15 Queens Building
One inherent characteristic of nonlinear systems is the frequency-energy dependence of their oscillations. This presentation introduces an efficient algorithm, geared toward high-dimensional systems, for computing this frequency-energy dependence. The algorithm is illustrated using several examples, including a full-scale aircraft. The presentation also shows that the intentional use of nonlinearity may offer great opportunities for engineering design. In view of the frequency-energy dependence, essentially nonlinear vibration absorbers lack a preferential resonance frequency, a feature that cannot be achieved with the linear tuned mass damper. The absorber performance is examined by considering the suppression of aeroelastic instability.
Gaëtan Kerschen
Gaëtan Kerschen is an Associate Professor in the Aerospace and Mechanical Engineering Department at the University of Liège, where he is also the head of the Space Structures and Systems Laboratory. In 2003, he earned a Ph.D. in Aerospace Engineering from the University of Liège. In 2003 and 2004, he was a visiting postdoctoral fellow at National Technical University of Athens and at the University of Illinois at Urbana-Champaign. He is currently a member of the editorial boards of the Journal of Small Satellites and Mechanical Systems and Signal Processing Journal. His current and past research work has dealt with nonlinear oscillations, structural health monitoring, finite element model validation, signal processing, system identification and thermal radiation.
Date: 15/2/2011
Time: 2pm
Location: 0.35 Andrew Robertson Room
In this seminar, the flows around realistic configurations of helicopters are considered. These are problems of industrial relevance as well as interesting areas for fundamental fluid dynamics research. Within the helicopter flow, transition to turbulence, massive separation, stall and transonic phenomena co-exist with aeroacoustics and aeroelasticity.
To date, the flow around a helicopter is still a formidable challenge for theoretical analyses and Computational Fluid Dynamics computations. Following a systematic validation approach of the CFD for fundamental flow cases, confidence in the predictions is built and blind comparisons of CFD with experimental data as well as flight-tests were made. The seminar presents an overview of the efforts of the Liverpool lab over the past years towards building the capability to analyse and predict helicopter flows. Along the way, fluid mechanics and aerodynamics phenomena were investigated including: tip flows and vortices, blade-vortex interaction, dynamic stall, transonic flow, bluff body flow, and wakes. These problems present true challenges for CFD methods and consequently new CFD techniques had to be developed. In addition, the complex flow physics of each individual phenomenon merits a separate investigation. During the seminar, the current state-of-the-art will be presented with respect to the analysis of helicopter flows with CFD along with highlights of fundamental flow phenomena that need to be adequately resolved before routine industrial predictions.
Professor George Barakos obtained a Diploma in Engineering from the National Technical University of Athens in 1992. His diploma thesis was on the numerical simulation of turbulent buoyant flows. In 1994, he received a Masters of Applied Science in Chemical Engineering from the University of Ottawa, where he developed finite element methods for Non-Newtonian viscoelastic flows with free surfaces. George completed his studies in 1999 after receiving a Ph.D. from the Department of Mechanical Engineering of the University of Manchester Institute of Science and Technology (UMIST), with a Ph.D. thesis on the modelling of unsteady, turbulent aerodynamic flows.
As a post-doctoral researcher he worked on fluid-structure interaction problems at the Engineering Department of Queen Mary and Westfield College. His research on wing flutter problems and external aerodynamics was funded through the Framework 5 EC project UNSI. He continued his career at the Department of Mechanical Engineering at Imperial College (Rolls-Royce Vibration Technology Centre) as a Research Associate, working on turbomachinery flows, high performance computing and unstructured grid methods, in close collaboration with the Rolls-Royce company.
In 2001 he was appointed Lecturer at the Aerospace Department of the University of Glasgow and established research in CFD, parallel computing, turbulence modelling, fluid structure interaction and unsteady aerodynamic flows. The main application area of his research is rotorcraft aerodynamics and aeromechanics, and he is currently leading the development of predictive methods for the Rotorcraft Aeromechanics DARP. George was promoted to Senior Lecturer at the same University in 2005. In November 2005, he joined the Engineering Department of Liverpool University, where the CFD laboratory of Glasgow was relocated, and he is currently leading the development of CFD methods for rotorcraft, wind turbines and weapon bay flows. He was promoted to Reader in November 2007 and became Professor in 2009. In December 2009,
George established the AgustaWestland-Liverpool Advanced Rotorcraft Centre to integrate research in CFD and simulation carried out at Liverpool with the research and development department of AgustaWestland. He is currently teaching undergraduate and graduate-level courses on Fluid Mechanics, Aerodynamics, Numerical Methods, Computational Fluid Dynamics and Thermodynamics, and is the director of the MSc and MRes degree programmes in Simulation in aerospace Engineering. George is the author of some 80 research papers and a regular contributor to national and international conferences on aerodynamics, fluid mechanics and CFD.