Paper accepted (Fusion Eng. Des.) on effective thermal conductivity

Title: Influence of gas pressure on the effective thermal conductivity of ceramic breeder pebble beds

Author(s): Weijing Dai, Simone Pupeschi, Dorian Hanaor, Yixiang Gan

Fusion Engineering and Design, in press. [DOI][PDF:045_FED_2017]

Figure: Gas pressure related size dependency of the contact units.

Abstract: Lithium ceramics have been considered as tritium breeder materials in many proposed designs of fusion breeding blankets. Heat generated in breeder pebble beds due to nuclear breeding reaction must be removed by means of actively cooled plates while generated tritiums is recovered by purge gas slowly flowing through beds. Therefore, the effective thermal conductivity of pebble beds that is one of the governing parameters determining heat transport phenomenon needs to be addressed with respect to mechanical status of beds and purge gas pressure. In this study, a numerical framework combining finite element simulation and a semi-empirical correlation of gas gap conduction is proposed to predict the effective thermal conductivity. The purge gas pressure is found to vary the effective thermal conductivity, in particular with the presence of various sized gaps in pebble beds. Random packing of pebble beds is taken into account by an approximated correlation considering the packing factor and coordination number of pebble beds. The model prediction is compared with experimental observation from different sources showing a quantitative agreement with the measurement.

Keywords: effective thermal conductivity; ceramic breeding materials; pebble beds; granular materials; gas pressure

Full paper can be downloaded via Publications page.

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Ms Yongmei Zhang joined the group

Ms Yongmei Zhang has just started her PhD program in March, 2017, and she will work on the mechanics of interfaces. Yongmei graduated with Master of Engineering in Solid Mechanics from the School of Aerospace, Xi’an Jiaotong University, China in 2016.

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PostDoc Opening in Carbon Storage

A postdoctoral research associate in carbon storage has been advertised in the School of Civil Engineering, Faculty of Engineering and IT at the University of Sydney. The official advertisement by The University of Sydney can be found via https://goo.gl/wqsvLl

The Postdoctoral Research Associate will undertake a project funded by the Australian Research Council on CO2 storage, named “Assessing reservoir performance for carbon storage in saline aquifers.” The Chief Investigators include A/Professor Luming Shen, Dr Federico Maggi, Dr Yixiang Gan, Professor Abbas El-Zein, Dr Zhejun Pan.


The project aims at developing and testing a modelling framework to assess the injectivity, storage capacity, and containment of supercritical CO2 injected in deep saline aquifers.The project broadly covers multiphase flow in porous/fractured geological materials, and emphasizes physical, hydraulic, and geomechanical processes at multiple spatial and temporal scales. The project is expected to provide a validated computational framework that can be used by stakeholders to improve analysis and assessment of reservoir performance under various scenarios of CO2 injection operations and boundary environmental conditions. This opening is fundamentally based on the development of advanced computational frameworks but it is part of a greater effort that also involves in-situ data collection and experimental laboratory tests conducted by other participants to this project. The project is led by A/Prof Luming Shen in the School of Civil Engineering at the University of Sydney, and involves the collaboration of the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia.

 

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ModVal14, Karlsruhe, Germany

From 2-3 March, 2017, Dr Gan attended the 14th Symposium on Fuel Cell and Battery Modeling and Experimental Validation (ModVal14), Karlsruhe, Germany. In the conference, the recent work in the research group on “Universality of the emergent scaling in finite random binary percolation networks” was presented.

The presentation slides can be viewed and downloaded via:

2017_Gan_ModVal14_s

 

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Paper accepted (PLOS ONE) on RC networks

Title: Universality of the Emergent Scaling in Finite Random Binary Percolation Networks

Author(s): Chongpu Zhai, Dorian Hanaor, Yixiang Gan

PLOS ONE, in press. [DOI:10.1371/journal.pone.0172298]

Figure: (Left) A lattice network containing randomly distributed resistors and capacitors; (Right) Normalised admittance module as a function of frequency.

Full paper can be downloaded via Publications page.

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Visitors from KIT

Mr Simone Pupeschi and Mrs Marigrazia Mascardini are visiting us from Karlsruhe Institute of Technology (KIT), Germany from Jan to April, 2017. They have previously visited us in 2015, with the photo attached from their last visit. 

Simone and Mari are two final-year PhD students at KIT and have been working on thermo-mechanical behaviour of tritium breeder materials under extreme loading conditions (high temperature and neutron irradiation) for nuclear fusion reactors (i.e., ITER and Fusion for Energy projects). 

Photo from a Thai dinner taken on 1/2/2017, from left: Simone, Ratna, Yixiang, Mari and Simon.

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Inaugural Sydney Research Accelerator (SOAR) Fellows launch

Last week, Dr Gan attended the launch event of the Inaugural Sydney Research Accelerator (SOAR) Fellows. The fellows from the University’s new Sydney Research Accelerator (SOAR) program came together last week for a networking morning tea with the Vice-Chancellor, Dr Michael Spence, and Deputy Vice-Chancellor (Research), Professor Duncan Ivison.

In its first year, the program will enable 10 early-career and 10 mid-career researchers to further their research in important areas such as preventing melanoma, preparing for the next global pandemic, building more powerful batteries for electric cars and helping those from disadvantaged backgrounds access education.

Group photo (from left): Deputy Vice-Chancellor (Research) Professor Duncan Ivison with SOAR Fellows Associate Professor Xiaoke Yi, Associate Professor Karl Maton, Dr Yixiang Gan, Associate Professor Chris Ling, Dr Wojciech Chrzanowski, Associate Professor Tara Murphy, Dr Stefanie Schurer, Dr Jane Lê, Associate Professor Paulo Ferreira, Associate Professor Michael Valenzuela, Associate Professor Anne Cust, Associate Professor Susan Park, Associate Professor Anika Gauja.

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A few photos from the event (1/12/2016).

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IWMEM2016 workshop

International Workshop on Mechanics of Energy Materials (IWMEM2016) has been successfully hosted at The University of Sydney, 14-15 November, 2o16.

The workshop contained 22 presentations, regarding a wide range of research on challenging engineering problems in energy systems, and 40 participants from Germany, China, India, USA and Australia. After the presentations, an open discussion session has been carried out for variety of questions faced in the current trends in energy systems, and the plan to host the next IWMEM in Suzhou, China, 2017.

The group photo is taken in front of The University of Sydney Quadrangle.

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Also, there are some photos during our open discussion sessions:

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Mingchao awarded Endeavour Research Fellowship

Our previous visiting PhD student, Mr Mingchao Liu,from Tsinghua University has been awarded with Endeavour Research Fellowship from Australian Government. This prestige fellowship will support him to conduct a six-month research project at The University of Sydney in 2017.

Congratulations to Mingchao.

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More details about Endeavour Scholarships and Fellowships (link):

The Endeavour Scholarships and Fellowships are the Australian Government’s competitive, merit-based scholarships and fellowships providing opportunities for Australians to undertake study, research or professional development overseas and for overseas citizens to do the same in Australia.

The Endeavour Scholarships and Fellowships build Australia’s reputation for excellence in the provision of education and research, support the internationalisation of the Australian higher education and research sectors and offer high-achieving Australians opportunities to increase their knowledge and expertise in their field.

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Dr Gan selected as Sydney Research Accelerator fellow

Dr Gan has been selected as one of the inaugural Sydney Research Accelerator (SOAR) fellows at The University of Sydney. The news has just been announced by the University.

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SOAR stands for Sydney Outstanding Academic Researcher program.

Extracted from the announcement (link):

The first cohort of fellows of the University’s new Sydney Research Accelerator (SOAR) program has been announced.

In its first year, the program will enable 10 early-career and 10 mid-career researchers to further their research in important areas such as preventing melanoma, preparing us for the next global pandemic, building more powerful batteries for electric cars and helping those from disadvantaged backgrounds succeed in education.

As part of their two-year program, fellows are awarded $50,000 per year to support their research, innovation and development plans. They also benefit from a personalised program of research development support and structured mentoring.

Deputy Vice-Chancellor (Research) Professor Duncan Ivison said the program recognises and develops the University’s most talented researchers as part of the University’s 2016-20 unprecedented investment in research.

“Through SOAR, we will support up-and-coming research leaders to build momentum and increase the scale and impact of their research.”

“At the University of Sydney, we want to celebrate and nurture high-performing researchers to realise their full potential and SOAR is just one of the many new programs we are developing to do just that.”

Professor Ivison said the program would allow our best and most promising researchers more opportunity to fast-track their career development and position them as pioneers in new fields. It will help them build leadership skills and aid the development of new partnerships with industry and other leading academics around the world.

Dr Andrew Black, Director of Research Development and Collaboration, said the program received an overwhelming level of interest.

“The volume and calibre of the applicants was extremely high, which highlights the University’s ability to attract leading researchers across a variety of disciplines. With the demand and early success of the program, we hope to increase the number of fellowships offered in 2018.”

Highlighting the University’s commitment to gender equity, 50 percent of the fellowships were awarded to women.

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Saba won 1st Prize in Civil Poster Presentation 2016

Congratulations to Mrs Saba Gharehdash, who won Annie B Wilson 1st Prize in Civil Engineering Poster Presentation 2016 last Friday. The presentation is entitled “Mechanical and Hydraulic Behaviour of Blast Induced Fractured Rock”. She is a PhD candidate supervised by A/Prof Luming Shen and Dr Yixiang Gan.

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Professor Marc Kamlah is visiting the lab

My former PhD advisor, Professor Marc Kamlah from Karlsruhe Institute of Technology (KIT) Germany, is visiting the lab for four weeks. Marc is the group leader and now acting as the head of Institute of Applied Materials – Mechanics of Materials and Biomechanics (IAM-WMB) where over 60 Scientists work experimentally and theoretically in the field of the mechanics of materials and bio-mechanics. More details about IAM-WMB via https://www.iam.kit.edu/wbm/index.php

He will attend later the International Workshop on Mechanics of Energy Materials (IWMEM 2016) at The University of Sydney.

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Chongpu presented at IEEE Holm Conference and won Young Investigator Award

Mr Chongpu Zhai (a PhD candidate) presented our work on “Stress-dependent frequency response of conductive granular materials” at The IEEE Holm Conference on Electrical Contacts (9-12 October, 2016, Florida USA) and won the Young Investigator Award.

Well done and Congratulations, Chongpu.

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The paper was co-authored by Chongpu Zhai, Dorian Hanaor, Gwénaëlle Proust, and Yixiang Gan, at The University of Sydney.

Conference website: http://www.ieee-holm.org/

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Mr Oleg Birkholz is visiting the lab

Mr Oleg Birkholz from Karlsruhe Institute of Technology (KIT), Germany is visiting us at The University of Sydney. Oleg is working on the numerical aspects of modelling lithium-ion battery systems, via the discrete element method and resistor-capacity (RC) network. He will stay with us for two months and working on modelling electro-mechanical properties of granular energy systems.
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Conference presentations (ICTAM and SOFT)

Recently, two previous visitors (Mingchao and Mari) have presented their work at two conferences.

(1) In August, Mr Mingchao Liu (Tsinghua University, China) attended the 24th International Congress of Theoretical and Applied Mechanics (ICTAM2016) in Montreal, Canada, presenting “Surface effect on the adsorption-induced deformation of ordered porous materials”.

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(2) In September, Mrs Marigrazia Moscardini (Karlsruhe Institute of Technology, Germany) attended the 29th Symposium on Fusion Technology (SOFT 2016) in Prague, Czech Republic, presenting “Discrete element modelling of ellipsoidal particles for fusion applications”.

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Manuscript accepted (Langmuir)

A manuscript has been accepted by Langmuir on a theoretical analysis of capillary penetration in porous media: 

Liu, M., Wu, J., Gan,Y., Hanaor, D., Chen, C. (2016). Evaporation limited radial capillary penetration in porous media. Langmuir. in press.

DOI: 10.1021/acs.langmuir.6b02404

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Figure: (a) Schematic illustration of an annular porous medium fed by inner and outer reservoirs. (b) Calculated phase diagram of evaporation limited radial capillary penetration in an annular porous medium.

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Ms Yi Zhang submitted MPhil thesis

Ms Yi Zhang has just submitted her MPhil thesis, on “Static and Dynamic Behaviour of Inter-granular Liquid Bridges: Hysteresis of Contact Angle and Capillary Forces”, at School of Civil Engineering, The University of Sydney, and this is our research group.

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31.08.2016

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Manuscript accepted (FED)

A manuscript has been accepted by Fusion Engineering and Design, summarising Simone’s work during his stay at The University of Sydney, funded by a Go8-DAAD project. Simone is working at Karlsruhe Institute of Technology, Germany.

Pupeschi, S., Knitter, R., Kamlah, M., Gan, Y. (2016) Numerical and experimental characterization of ceramic pebble beds under cycling mechanical loading. Fusion Engineering and Design. in press.

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Paper online, TAML

Liu, M., Jin, P., Xu, Z., Hanaor, D.A.H., Gan, Y., Chen, C.Q. (2016)  Two-dimensional modeling of the self-limiting oxidation in silicon and tungsten nanowires. Theoretical and Applied Mechanics Letters. in press. [DOI]

TAML2016

Abstract: Self-limiting oxidation of nanowires has been previously described as a reaction- or diffusion-controlled process. In this letter, the concept of finite reactive region is introduced into a diffusion-controlled model, based upon which a two-dimensional cylindrical kinetics model is developed for the oxidation of silicon nanowires and is extended for tungsten. In the model, diffusivity is affected by the expansive oxidation reaction induced stress. The dependency of the oxidation upon curvature and temperature is modeled. Good agreement between the model predictions and available experimental data is obtained. The developed model serves to quantify the oxidation in two-dimensional nanostructures and is expected to facilitate their fabrication via thermal oxidation techniques.

Keywords: Self-limiting oxidation; Finite reactive region; Kinetics model; Nanowires

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Paper online, IJMMD

Flores-Johnson, E.A., Wang, S., Maggi, F., El Zein, A., Gan, Y., Nguyen, G.D., Shen, L. (2016) Discrete element simulation of dynamic behaviour of partially saturated sand. International Journal of Mechanics and Materials in Design. in press. [DOI]

 

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Abstract
The discrete element method (DEM) together with the finite element method (FEM) in LS-DYNA was employed to investigate the dynamic behaviour of sand under impact loading. In this approach, the partially saturated sand was modelled in DEM with capillary forces being taken into account through an implicit capillary contact model, while other solids were simulated using FEM. A slump test was first performed with dry sand to calibrate the contact parameters in DEM. Low velocity impact tests were then conducted to investigate the effect of water saturation on the shape and height of sand piles after impact, and to validate the simulations. It was found in the experiments that an increasing water saturation (in the range between 10 and 30 %) affected the height of sand pile for a given drop height due to an increasing cohesion between particles. The simulations captured the experimental ejecta patterns and sand pile height. Finally, a low confinement split Hopkinson pressure bar test from earlier literature was modelled; the DEM–FEM simulations could reproduce the trends of experimentally observed stress–strain curves of partially saturated sand under high strain rate loading, indicating that it was feasible to model dynamic behaviour of dry and wet sand with low saturation (<20 %) in LS-DYNA; however, a number of questions remain open about the effect of grain shape, grain crushing and viscosity.

Keywords: Partially saturated sand; Impact; Capillary force; Discrete element method; DEM–FEM simulation; LS-DYNA

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