Research Seminars 2017

Date

Time & Venue

Speaker(S)

Topic

27/02/2017

12-1pm

Civil Engineering Lecture
Room 1

Prof Qingwei Ma
City, University of London

Towards multiscale multimodel simulation of fluids and their interaction with structures in marine engineering

17/03/2017

Prof Jianlei Niu
The University of Sydney

Building environment and energy efficiency - relevance to public health, sustainability and city liveability

31/03/2017

Prof Richard Flay
The University of Auckland

Integration of wind tunnel pressure measurements with the structural model for a large roof

14/04/2017

Dr David Lo Jacono
Institut de Mecanique des Fluides de Toulouse, France

Vortices of V. Strouhal

Seminar Cancelled

28/04/2017

Mr Shengyang Chen
The University of Sydney

Hypolimnetic oxygenating and epilimnetic mixing in a shallow, eutrophic drinking-water reservoir

12/05/2017

Dr James Baker
The University of Sydney

Roll waves and particle size-segregation in dense granular flows

26/05/2017

Dr Yongling Zhao
The University of Sydney

Instability and transition of natural convection boundary layers

09/06/2017 Mr Haoyu Wang
The University of Sydney

Passive solar thermal strategies for building ventilation and thermal comfort

Seminar Cancelled

23/06/2017

Prof Ivan Marusic
The University of Melbourne

High Reynolds number wall turbulence: Universality, structure and interactions


All are welcome to attend and/or present!

Please direct enquiry to A/Prof Chengwang Lei.
Tel: (02) 9351 2457, Email: Chengwang.Lei@sydney.edu.au


Towards multiscale multimodel simulation of fluids and their interaction with structures in marine engineering

27 February 2017

Prof Qingwei Ma
School of Mathematics, Computer Science and Engineering
City, University of London

Abstract
The presentation will summarise the progress of developing the multiscale multimodel simulation of fluids and their interaction with structures in marine engineering. The multimodel methods include the combination of potential and viscous models, potential models of different approximate levels and viscous models of different approximate levels. The multimodel methods have been applied to various different situations, such as large scale ocean wave simulations, wave-structure interaction, vortex shedding and so on.

About the speaker
Professor Ma received his PhD degree from University College London, UK, is currently a Professor in Hydrodynamics and the Director of Research Centre for Fluid-Structure Interaction consisting about 25 staff and researchers in City, University of London. He is also Chair of Environmental Force Group (committee) of Society of Underwater Technology, UK and one of Board of Directors of the International Society of Offshore and Polar Engineers (ISOPE).

He and his team has been engaged in research on interaction between fluid/water-waves and structures for many years. Their focus is on studying nonlinear waves and their interaction with various marine structures. They have developed several advanced numerical methods. Due to his contribution in this area, he was granted the CH Kim Award by ISOPE in 2016.


Building environment and energy efficiency - relevance to public health, sustainability and city liveability

17 March 2017

Prof Jianlei Niu
School of AD&P and School of Civil Engineering
The University of Sydney

Abstract
Modern population spend over 90% of their time indoors and more than 1/3rd global energy consumption can be attributed to maintaining comfort and air quality in buildings. In this seminar, I will present our research on the understanding of the indoor environment, and the development and assessment of technologies that can maintain indoor comfort and environmental health in more energy-efficient ways. Technologies covered will include advanced air distribution methods, development of advanced thermal energy storage technologies, air-to-air heat recovery, advanced glazing and window systems, which are more related to the energy performance. The study of low-emission building materials and understanding the droplets dynamics for the control of airborne infection in built environments will be presented to address the public health concern. Finally, urban environment design, a multidisciplinary professional issue, will be presented, which is the theme of an on-going CRF (collaborative research project). The objective of the research is to create local outdoor thermal comfort to encourage outdoor activities of urban residents, and it will be shown that the application of computer simulation to enable quantitative urban planning will be a paradigm-shift needed for our future cities.

About the speaker
Dr Jianlei Niu is a con-joint Professor of Building Environment and Energy, School of Civil Engineering and School of AD&P, USyd. He received his BSc in HVAC Engineering and MSc in Thermal Engineering from Tsinghua University, and received his PhD in Mechanical Engineering from Delft University of Technology. He also had a unique industrial R&D working experience in UK. With an academic background in turbulence modelling and CFD (computational fluid dynamics) and building thermal performance simulation, he has obtained and completed nearly 20 research grants from various funding bodies, and published over 200 technical papers including over 100 internationally reviewed journal papers and gave a large number of invited lectures and presentations worldwide, some of which were sponsored by the ASHRAE Distinguished Lecturer scheme. He has successfully supervised over ten PhD students. His invention personalized ventilation technology has been patented in both China and USA, and won the Bronze award in 35th International Exhibition of Inventions, Geneva, Switzerland, and another patent PCM (Phase-change-material)-microcapsule–slurry-based thermal storage technology won him a gold award at the 38th event. He also provides specialist consultancy services to the local industry in data centre cooling design.

He serves as co-Editor-in-Chief of the Elsevier journal Energy and Buildings and sits in the editorial board of several SCI journals including Building and Environment, Building Simulation, International Journal of Sustainable Built Environment, and Building Performance Simulation, and he also serves as Scientific Committee Member for the international conference series Indoor Air, Building Simulation, Roomvent, and CLIMA. He was awarded fellowship by ASHRAE, CIBSE, HKIE, IBPSA and ISIAQ.


Integration of wind tunnel pressure measurements with the structural model for a large roof

31 March 2017

Professor Richard G.J. Flay
BE(Hons), PhD, FIMechE, FIPENZ, FRINA, MASME
University of Auckland
New Zealand

Abstract
Wind tunnel tests were performed on a 1:200 scale model of the long span west stadium canopy proposed for QBE Stadium in Auckland. The tests measured the pressures on the proposed roofing elements. These were then processed into pressure coefficients based on the tunnel wind speed. Selection of critical load cases was carried out by integrating for key metrics for this structure, defined as maximum base shears and overturning moments for the whole structure. The wind tunnel pressure data results for these critical load cases were then integrated directly with the structural analysis model. This approach enabled 10 unique load cases to be determined. It was found that this was a very effective way of determining the wind loads and designing an efficient structure to resist them.

About the speaker
Professor Flay studied Mechanical Engineering at the University of Canterbury, graduating BE (Mech) with 1st Class Honours in 1975. He then registered for his PhD at the same university and graduated in 1979 with a PhD in Wind Engineering. This was followed by a period of two years as a National Research Council Visiting Fellow at the Atmospheric Environment Service, Environment Canada, Toronto, where he worked with Dr Hans Teunissen, carrying out research in wind engineering using a Boundary Layer Wind Tunnel. He then moved to a consulting company in Toronto for a period of four years, where he was employed as an Aerodynamic Design Engineer, and carried out design work on many different kinds of wind tunnels, both subsonic and supersonic.

Since returning to New Zealand, Professor Flay joined the Mechanical Engineering Department in 1984 as a senior lecturer. He has been Professor of Mechanical Engineering since 2000. He is Director of the Yacht Research Unit, President of the Royal Institution of Naval Architects (NZ Division), and Chair of the 9th Asia Pacific Conference on Wind Engineering to be held in Auckland in December 2017.

His research interests are focused on the wind, and he has consulted and researched in the areas of wind engineering, wind energy, wind tunnel design, wind tunnel testing and sail aerodynamics. A highlight was his design of the world’s first wind tunnel capable of producing twisted flow for testing yacht sails. This wind tunnel was used by Team New Zealand, and helped them win the America’s Cup in 1995 and successfully defend it in 2000. More recently he has advised on the design of wind tunnels in England, Hong Kong, Australia, India and New Zealand. His main teaching areas are fluid mechanics, thermodynamics, aerodynamics, design, wind engineering and yacht engineering.

In 2015 the Wind Engineering Research Group moved to a new campus at Newmarket in Auckland, and Prof. Flay designed a large Boundary Layer Wind Tunnel with a test section 20 m long x 3.6 m wide x 2.5 m high which was completed in June 2015.The wind tunnel is used for teaching, research and commercial testing. Wind engineering studies are carried out in this wind tunnel using a 512-channel electronically scanned pressure system, several JR3 high frequency force balances, and pedestrian level wind investigations using Irwin probes and the erosion technique. The wind tunnel is also used for cycle aerodynamic drag testing and vehicle testing with a moving ground-plane under the model vehicle.

Prof. Flay’s more recent research has concentrated on wind flows over complex terrain, modelling wind loads on bridges, sail aerodynamics, turbine blade loading, loads on large roofs, extreme wind speeds for wind loading design in New Zealand, and the aerodynamics of buoyancy vortices in the atmosphere.


Vortices of V. Strouhal - (Seminar Cancelled)

14 April 2017

Dr David Lo Jacono
Institut de Mecanique des Fluides de Toulouse
France

Abstract
During this seminar, I will talk about the link between Strouhal's findings and vortices. We learn that the Strouhal number characterises the shedding frequency of vortices behind a bluff-body, yet Strouhal never encountered a vortex. I will try to show the role played by various well-known researchers (Rayleigh, Bénard, Kármán, etc.), and others that are less well known yet have a key role towards understanding wake dynamics. Starting from the motivation of Strouhal and ending with the modern analysis of wakes in 1930, I will try to build an incomplete and brief history of 19th-20th century (wake) fluid mechanics focussing on motivation and experimental insights. This work was originally part of my ScD dissertation and further completed for the recently held colloquium "A century of Fluid Mechanics 1870-1970" celebrating the IMFT century anniversary.

About the speaker
David Lo Jacono graduated from EPFL in 2005 while working on thermo-diffusive instabilities. He was then an academic visitor at Monash University as a Swiss National Science Fellow working on bioengineering problems. Later, as an ARC Fellow he worked on bluff-body and wind turbine wake problems within the Department of Mechanical and Aerospace Engineering. Since, 2009, David Lo Jacono is working at l’Institut de Mécanique des Fluides de Toulouse (IMFT-CNRS), associated with l’Université Paul Sabatier, in Toulouse, France.


Hypolimnetic oxygenating and epilimnetic mixing in a shallow, eutrophic drinking-water reservoir

28 April 2017

Mr Shengyang Chen
The University of Sydney

Abstract
Artificial mixing is often carried out in lakes and reservoirs for the purpose of oxygenation and destratification. Studies show that mixing can prevent deterioration of water quality caused by hypoxia and algal bloom in natural water bodies. Understanding the effects of artificial mixing induced by water-quality management systems on thermal structures and constituent transport can help to optimize the design and operation of the systems. The mixing generally results in an increase of dissolved oxygen in the water, as well as an increase of temperature in the deeper layers of the water bodies but a decrease of the temperature in the upper layers.

Bubble-plume and side stream pumping devices are two of the commonly used devices that have been shown to successfully mitigate water quality problems in many cases. To investigate the mixing mechanism involved in the system operation, in-situ whole-reservoir experiments were carried out for analyzing the three-dimensional (3-D) effects of artificial mixing in a shallow, eutrophic, drinking-water reservoir, where a bubble-plume epilimnetic mixer (EM) and a side-stream supersaturation oxygenation water-jet system (SSS) were deployed to operate concurrently. In addition, a semi-implicit 3-D hydrodynamic model (Si3D) coupled with bubble-plume and water-jet models was adopted to understand the findings from the field experiments. One of the objectives of the research is to accurately predict artificial mixing outcomes in natural water using the calibrated coupled Si3D, which are useful for water quality management.

About the speaker
Mr Shengyang (Chris) Chen is a PhD candidate in the School of Civil Engineering, The University of Sydney (USYD), working with Dr Chengwang Lei at USYD and Dr John Little at Virginia Tech (VT) in the USA. He received his BE in Water Supply and Drainage Engineering from Hunan University in China, MEngSc (Water, Wastewater, and Waste) from The University of New South Wales, and MPhil (Environmental Fluids) from USYD. He has expertise in modelling techniques (e.g. multiphase flow modelling using Computational Fluid Dynamics models) and in-situ sampling methods using CTD profilers and ADCP in lakes and reservoirs.

His PhD research project focuses on artificial mixing in lakes and reservoirs for water quality mitigation, which is an interdisciplinary research involving researchers from USYD, VT, and Western Virginia Water Authority. He visited VT as a graduate researcher in 2015 and 2016 respectively to carry out field measurements in a drinking-water reservoir in Virginia. Chris is a recipient of the William and Catherine Mcllrath Scholarship and an Australian Postgraduate Award from USYD. His PhD research is also supported by Fralin Life Sciences Institute and Global Change Centre at VT.


Roll waves and particle size-segregation in dense granular flows

12 May 2017

Dr James Baker
The University of Sydney

Abstract
Flows down inclined open channels can spontaneously develop periodic surface waves as small upstream disturbances grow as material moves downslope. The resulting pulses, referred to as 'roll waves', travel faster than the bulk flow and have important implications for hazard mitigation because their amplitudes and peak mass flux are significantly higher than the base flow from which they form. This roll-wave instability is commonly observed in turbulent water flows but can also occur in dense granular flows, where collections of discrete particles flow like a fluid when subject to sufficient stresses. Geophysical examples of such flows include snow avalanches, debris flows or pyroclastic currents, which typically each consist of particles with a wide range of shapes, sizes and densities. Granular flows are prone to segregate according to these properties, with particle size-segregation often being particularly striking and leading to the formation of regions with different frictional properties, which consequently has a feedback effect on the flow.

This study investigates the influence of particle size-segregation on the roll-wave instability in dense granular flows. Inclined chute experiments are carried out using a bidisperse mixture of large and small grains flowing over a rough bed. We observe the formation of roll waves propagating at constant velocities, dependent on the material composition, with larger particles being preferentially sheared towards the flow surface and wave crests. A simple continuum model, which bears many resemblances to the classical shallow-water equations but accounts for granular rheology and segregation, is proposed and able to qualitatively capture the experimental observations.

About the speaker
Dr James Baker obtained a Master of Mathematics (MMath) degree from the University of Oxford in 2012, before moving to the University of Manchester to complete his PhD in Applied Mathematics in 2016. His thesis examined the mechanics of granular avalanches using a combination of mathematical theory, numerical simulations and laboratory experiments. Last November James joined the University of Sydney’s School of Civil Engineering as a postdoctoral research associate, where he has been working within SciGEM to develop dynamic X-ray imaging techniques for visualisation of three-dimensional granular flows.

Instability and transition of natural convection boundary layers

26 May 2017

Dr Yongling Zhao
The University of Sydney

Abstract
Natural convection is a common flow phenomenon that arises from thermal surfaces such as the surface of the Earth, computer heat-sinks and the skin of the human body. A particular topic of continuous research interest is the instability and transition of the thermal boundary layer, which governs the laminar–turbulent transition of the boundary layer and in turn determines heat and mass transfer and aerodynamic properties.

This study investigates the instability and transition of natural convection boundary layers from an isothermally heated vertical flat surface using a combination of direct stability analysis (DSA) and particle image velocimetry (PIV) measurements. DSA is firstly carried out for two-dimensional boundary layers. Characteristic frequencies of the natural convection boundary layers at various Rayleigh numbers are determined and verified by random-mode and single-mode numerical perturbation experiments. Direct numerical simulation is then performed for three-dimensional boundary layers perturbed by Tollmien-Schlichting and oblique waves to investigate the K-type and H-type transitions. The typical aligned and staggered Λ-shaped vortices characterizing the K-type and H-type transitions are observed for the first time in pure natural convection boundary layers. The aligned Λ-shaped vortices are also verified by PIV results. Further analysis of turbulence energy production suggests that the turbulence energy production by buoyancy rather than the Reynolds stresses dominates the K-type and H-type transitions.

About the speaker
Dr Yongling Zhao obtained a Master of Philosophy (MPhil) degree from the University of Adelaide in 2011, before moving to the University of Sydney to complete his PhD in Fluid Mechanics in 2015. His PhD thesis examined the instability and transition of natural convection boundary layers using a combination of direct stability analyses and PIV measurements. After one year working in industry as an R&D supervisor, Yongling joined the Centre for Wind, Waves and Water as a postdoctoral research associate, where he has been working with A/Prof Chengwang Lei and Prof John Patterson on buoyancy driven flows. Yongling was a recipient of the Australian Postgraduate Award, Civil Engineering Foundation Governor's Scholarship, and the Certificate of Research Excellence 2013 from the University of Sydney.


Passive solar thermal strategies for building ventilation and thermal comfort - (Seminar Cancelled)

9 June 2017

Mr Haoyu Wang
The University of Sydney

Abstract
Passive thermal comfort strategies have been widely studied since the turn of the century. Among the passive thermal comfort strategies ever proposed, solar chimney and water wall stand out as two of the most popular topics in this field. However, some limitations are found in the applications of these two strategies. For example, conventional solar chimney only works during the day and prohibits lighting, whereas water wall introduces excessive heat during hot days and loses significant amount of heat during the night.

In this study, a novel strategy combining a solar chimney and a water wall is introduced. In the new strategy, a water wall replaces the absorber wall in the solar chimney and acts as an energy storage reservoir. During the day, part of the solar energy is used to induce ventilation while the rest is stored by the water wall. When solar radiation is not available, for example, during the night, the water wall serves as a backup heat source and releases the stored heat to the solar chimney to extend the period of ventilation. The performance of this integrated structure will be studied using thermal network analysis, numerical simulations and laboratory experiments, and will be compared with that obtained with a standalone solar chimney or a water wall. The effects of surface tinting, water colour and different configurations on the performance of the integrated structure will also be investigated.

About the speaker
Mr Haoyu Wang is a PhD candidate in the School of Civil Engineering, the University of Sydney. He received a Bachelor degree in Thermal Energy and Power Engineering from Shanghai Jiao Tong University, China, in 2014 and a Master degree in Energy Science, Technology and Policy from Carnegie Mellon University, USA, in 2015. Before joining the University of Sydney in August 2016, he worked as an intern at the Industrial Burner Department at Shanghai Marine Diesel Engine Research Institute, China, and engaged in numerical analysis of industrial products. Under the supervision of A/Prof Chengwang Lei, he is now working on a project focusing on passive thermal comfort strategies and the associated conjugated thermal boundary layer problem.


High Reynolds number wall turbulence: Universality, structure and interactions

23 June 2017

Prof Ivan Marusic
The University of Melbourne

Abstract
A key consideration in the characterization of the mechanics of turbulent flows is to understand the generation, evolution and interactions of the large-scale structures and the range of eddying motions that make up the turbulent flow. The non-linearity of these processes makes the problem very challenging, both computationally and experimentally. This is particularly true in wall-bounded flows where an increasing hierarchy of energy-containing eddy scales exists with increasing Reynolds number.

In this talk we will review recent studies in high Reynolds number flow facilities and from the atmospheric surface layer documenting unique high Reynolds number phenomena in wall turbulence. The focus will be the logarithmic region, looking at issues regarding its universality, coherent structures and how they interact across the boundary layer. These findings lead to a new consideration of so-called “inner-outer” interactions and form the basis of a predictive model for the near-wall inner region and the wall-shear stress. The implications of this model will be discussed.

About the speaker
Professor Ivan Marusic is an Australian Research Council Laureate Fellow and Redmond Barry Distinguished Professor in the Department of Mechanical Engineering at the University of Melbourne. He received his PhD in 1992 and BE (Hons) Mech in 1987 from the University of Melbourne. His research is primarily in experimental and theoretical studies of turbulence at high Reynolds numbers. This includes studies in atmospheric surface layer flows and aquatic ecosystems. Prior to arriving in Melbourne in 2007 as an ARC Federation Fellow he was a faculty member at the University of Minnesota, where he was a recipient of an NSF Career Award and a Packard Fellowship in Science and Engineering. He is an Associate Editor of the Journal of Fluid Mechanics, and a Fellow of the American Physical Society and the Australasian Fluid Mechanics Society. In 2014 he was elected as a Fellow of the Australian Academy of Science.