http://espace.library.uq.edu.au/ The University of Queensland en Fez http://blogs.law.harvard.edu/tech/rss http://espace.library.uq.edu.au/view/UQ:149943 2008-06-06T00:00:00Z Dietrich, C. R. og Walker, A. og Scoccimarro, M. og Ross, H. og Trisophon, K. http://espace.library.uq.edu.au/view/UQ:23903 The artificial dissipation effects in some solutions obtained with a Navier-Stokes flow solver are demonstrated. The solvers were used to calculate the flow of an artificially dissipative fluid, which is a fluid having dissipative properties which arise entirely from the solution method itself. This was done by setting the viscosity and heat conduction coefficients in the Navier-Stokes solvers to zero everywhere inside the flow, while at the same time applying the usual no-slip and thermal conducting boundary conditions at solid boundaries. An artificially dissipative flow solution is found where the dissipation depends entirely on the solver itself. If the difference between the solutions obtained with the viscosity and thermal conductivity set to zero and their correct values is small, it is clear that the artificial dissipation is dominating and the solutions are unreliable. 2007-07-12T00:00:00Z Macrossan, M. N. og Hancock, M. http://espace.library.uq.edu.au/view/UQ:298145 2013-04-23T12:05:38Z Philippe Lorrain og Stefan Brieschenk og Bianca Capra og Russell Boyce http://espace.library.uq.edu.au/view/UQ:264524 Sparse-Lagrangian filtered density function (FDF) simulations using a generalized multiple mapping conditioning mixing model and density coupling via a conditional form of the equivalent enthalpy method are performed for both constant density and variable density turbulent jet diffusion flames. The consistency between the sparse-Lagrangian FDF for the reactive species and the Eulerian large eddy simulation (LES) for velocity along with the accuracy of the reactive species predictions relative to the exact equilibrium solution are presented in detail. The sensitivity to the number of particles used in the simulations, the mixing localization structure, chemistry and numerical time step are all investigated. The analysis shows that consistency between the FDF and LES fields is relatively insensitive to the sparseness of the particle distributions and other model parameters but that the reactive species are strongly dependent on the degree of mixing localization in the LES mixture fraction space. An algorithm is developed to control the localization for any sparse distribution of particles with inter-particle distances within the inertial range, and it is shown that reactive species predictions are sensitive to the mixing distance in a reference mixture fraction space while there is very low sensitivity to the number of particles used in the simulations. 2012-01-08T00:00:00Z Cleary, M. J. og Klimenko, A. Y. http://espace.library.uq.edu.au/view/UQ:221859 A method of improving the adhesion of carbon thin films deposited using a cathodic vacuum arc by the use of implantation at energies up to 20 keV is described. A detailed analysis of carbon films deposited onto silicon in this way is carried out using complementary techniques of transmission electron microscopy and x-ray photoelectron spectroscopy (XPS) is presented. This analysis shows that an amorphous mixing layer consisting of carbon and silicon is formed between the grown pure carbon film and the crystalline silicon substrate. In the mixing layer, it is shown that some chemical bonding occurs between carbon and silicon. Damage to the underlying crystalline silicon substrate is observed and believed to be caused by interstitial implanted carbon atoms which XPS shows are not bonded to the silicon. The effectiveness of this technique is confirmed by scratch testing and by analysis with scanning electron microscopy which shows failure of the silicon substrate occurs before delamination of the carbon film. 2010-11-21T00:00:00Z Gerstner, E. G. og McKenzie, D. R. og Puchert, M. K. og Timbrell, P. Y. og Zou, J. http://espace.library.uq.edu.au/view/UQ:253771 Tool wear manifests in change of roughness of roll surfaces and governs the surface quality of both coated and uncoated products. Decrease of friction and wear in the roll–strip interface will stabilize the performance of the cold roll forming (CRF) mill and ensure uniform process output. The scope of this paper includes an experimental study of adhesive wear of hardened tool steel blocks sliding against a mild steel wheel and field observation of tool wear in the CRF of zinc coated mild steel. Wear mechanisms are identified for the materials interacting during the CRF process. The results include an empirical value of tool wear coefficient for D2 steel sliding against unlubricated uncoated hot rolled AISI C1020 mild steel. 2011-10-02T00:00:00Z Galakhar, Alexander S. og Gates, Jeffrey D. og Daniel, William J. T. og Meehan, Paul A. http://espace.library.uq.edu.au/view/UQ:139544 An adiabatic testing procedure for determining the self-heating propensity of coal has been evaluated using New Zealand coals. Repeatability of the self-heating rate (R-70), Obtained by the method, is less than +/-5% of the average value for tests performed consecutively over 3-4 days. For longer time periods, even using samples under controlled storage, the self-heating rate value decreases noticeably due to pre-oxidation effects. This pre-oxidation effect can be described by the equation R-70(t) = at(b), where t is the time in days, b a constant dependent on storage method and particle size and a the R-70 value of fresh coal. When stored samples are used for analysis, knowledge of this relationship can be used to extrapolate a fresh coal R-70 value by doing repeated tests over time. (C) 2000 Elsevier Science B.V. All rights reserved. 2008-06-10T00:00:00Z Beamish, BB og Barakat, MA og St George, JD http://espace.library.uq.edu.au/view/UQ:101888 2007-08-23T00:00:00Z Smith, Z. V. og McAree, P.R. http://espace.library.uq.edu.au/view/UQ:218219 Nowadays mining projects are seeking new versions of evaluation that are based on the flexibility in the project. Real option valuation (ROV) is one of the modern evaluation methods that provides a tool to adapt and revise mining projects under uncertainty and future variable movements. Most evaluation approaches simply assume that some variables are fixed, such as production rate, variable cost, fixed cost and lifetime of project. The first section of this paper reviews a comprehensive study of ROV in mining projects. The paper then introduces a new model that solves problems where previous methods lacked. The new method endeavours to find maximum mining project value by adding total cost as a function of production rate into ROV. The second section has been applied to a new model on the Century zinc mine in north-west Queensland, thus illustrating the future overview of that mine. The new version of ROV gave a significant positive value for the Century Mine, when the closure and reopening options where available throughout the life of the mine. Consequently, the new method evaluates real options to add value to mining projects, maximising project’s value, estimating cost function, optimising production rates and offers opportunities in projects to amplify gains or to mitigate losses. 2010-10-11T00:00:00Z Shafiee, S. og Topal, E. og Nehring, M. http://espace.library.uq.edu.au/view/UQ:270693 2012-03-20T00:00:00Z Saulov, D. N. og Rudolph, V. og Klimenko, A. Y. http://espace.library.uq.edu.au/view/UQ:201989 2010-04-08T10:24:36Z http://espace.library.uq.edu.au/view/UQ:100036 2007-08-23T00:00:00Z Hood, M. http://espace.library.uq.edu.au/view/UQ:148593 2008-06-06T00:00:00Z Butcher, A. R. og Helms, T. og Gottlieb, P. http://espace.library.uq.edu.au/view/UQ:255688 A possibility of a rigid flat plate that is placed in the wake of a square cylinder for a passive sound control is investigated numerically. The changes in the sound generation with gap distances are inspected at a Reynolds number of 150 and a Mach number of 0.2 for a constant plate length of D. Two regimes that significantly effects the sound generation are identified. The first regime, i.e. pre-vortex regime, is for 0 G 2.3D and the second regime, i.e. post-vortex regime, is for 2.4D G 7D. A sound reduction can be obtained in pre-vortex regime, where about 2.9 dB sound reduction is obtained when there is no gap between the two bodies. Contrary, at least an increase 8.0 dB sound level is emitted when the plate is placed in the post-vortex regime. Despite of that, a 6.3 dB sound reduction is obtained when the plate length is reduced to 0.26D and placed at 5.6D downstream of the cylinder. The sound reduction is limited by the deformation in the sinusoidal signal of the plate due to the unsteady plate stall process. 2011-10-13T00:00:00Z Ali, Mohamed Sukri Mat Ali og Doolan, Con J. og Wheatley, Vincent http://espace.library.uq.edu.au/view/UQ:229229 The generation of aeolian tones by the interaction of a low Reynolds number, low Mach number flow with a rigid square cylinder attached to a rigid thin flat plate is numerically investigated. When the length of the plate is varied from L = 0:5D to 6D, where D is the side length of the square cylinder, the results can be grouped into three distinct regimes. For the first regime (L . D), the aoelian tone levels decrease with increasing plate length. For the second regime (2D . L . 4D), the aeolian tone levels are always higher than the single square cylinder case and they increase with increasing plate length. For the third regime (5D . L . 6D), the levels of the aeolian tones decrease as the length of the plate increases but the levels are higher than the other regimes. These acoustic results can be explained in terms of the fluid mechanics occuring in the near wake of the cylinder. 2011-02-15T00:00:00Z Ali, Mohamed Sukri Mat og Doolan, Con J. og Wheatley, Vincent http://espace.library.uq.edu.au/view/UQ:97171 2007-08-24T00:00:00Z Jokic, M. D. og Daniel, W. J. T. og Asokanthan, S. F. og Mee, D. J. http://espace.library.uq.edu.au/view/UQ:12294 Stalker (AIAA Paper 87-0403) has suggested that, by ejecting molecules directly upstream from the entire face of a satellite, it is possible to reduce the drag on a satellite in low-Earth orbit and hence maintain orbit with a total fuel mass (for forward ejection and conventional reaction rockets) less than the typical mass requirements of conventional rockets. An analytical analysis is presented here, as well as Monte Carlo simulations. These indicate that to reduce the overall drag on the satellite significantly, collisions between the freestream and ejected molecules must occur at least two satellite diameters upstream. This can be achieved if the molecules are ejected far upstream from the satellite’s surface through a sting that projects forward from the satellite. Using some estimates of what would be feasible sting arrangements, we find that the drag on the satellite can be reduced to such an extent that the satellite’s orbit can be maintained with a total fuel mass of less than 60% of that required for reaction rockets alone. Upstream ejection is effective in reducing the drag for freestream Knudsen numbers less than approximately 250, but not otherwise. 2007-02-05T00:00:00Z G. P. Cathcart og M. N. Macrossan http://espace.library.uq.edu.au/view/UQ:209370 2010-07-21T00:00:00Z Houwing, A. F. P. og Gai, S. L. og Mudford, N. R. og Sandeman, R. J. og Boyce, R. R. http://espace.library.uq.edu.au/view/UQ:68891 Two new implementations of a tethered satellite system to provide aeroassist during a planetary flyby are investigated. In each mission scenario the interaction of the Martian atmosphere with an aerodynamic lifting surface, which is tethered to an orbiter, is used to perturb the flight path of the system. The aerodynamic forces generated by interacting with the atmosphere augment the gravity assist provided by the planet. In the first aerogravity-assist maneuver the tethered satellite system has congruent post- and preflyby configurations. The second scenario, which is referred to as a dual-destination mission, involves the system mass being separated during the flyby. Both of these aerogravity-assist maneuvers are shown to facilitate significant, propellant-free velocity changes. 2007-08-15T00:00:00Z Jokic, MD og Daniel, WJT http://espace.library.uq.edu.au/view/UQ:96124 2007-08-24T00:00:00Z Jokic, M. D. og Asokanthan, S. F. og Daniel, W. J. T. og Mee, D. J. http://espace.library.uq.edu.au/view/UQ:258983 2011-10-22T00:00:00Z Zhang, Jun og Elsanousi, Ammar og Lin, Jing og Huang, Yang og Elssfah, E. M. og Chen, Dongfeng og Gao, Jianming og Huang, Zhixin og Ding, Xiaoxia og Tang, Chengcun http://espace.library.uq.edu.au/view/UQ:196617 This research focusses on the aerothermodynamics of hypersonic vehicles - a field in which Australia maintains world leadership in niche areas. In particular, we are concerned with the complex flow structures that occur in both external and internal (scramjet engine) flowpaths associated with such vehicles, and for scramjet flowpaths, with the coupling between these structures and the combustion processes that lead to thrust generation. 2010-02-25T00:00:00Z Deepak, N. R. og Boyce, R. R. http://espace.library.uq.edu.au/view/UQ:9927 A new approach to DSMC collision modelling, called viscosity-DSMC or mu-DSMC, is described. The characteristic collision cross-section (of any standard collision model) is made to vary from cell to cell, based on the time-averaged temperature in each cell. In this way the collision model will display the Chapman-Enskog viscosity given by any desired viscosity law mu = mu(T), including a curve fit to experimental data. For example, we show that a hard sphere collision model, with hard sphere collision probability, used with a different molecular size in each cell, can reproduce a Sutherland viscosity law. Similarly, by making the reference cross-section of a VHS collision model a function of the temperature, we show that the VHS collision model can reproduce the viscosity given by the more complicated generalized hard sphere (GHS) collision model. We calculate the structure of a plane 1D shock using the new approach and show that the results agree closely with those from standard DSMC using the GHS model. A particularly simple, and computationally efficient, method is to use the Maxwell VHS model, in which all collision pairs are equally likely, as the basis of the new method. That is, the characteristic size of the maxwell VHS model is varied from cell to cell, based on the time-averaged cell temperature and the (arbitrary) desired viscosity law mu = mu(T). Since the time-averaged cell temperature is available in standard DSMC as part of the procedures which determine the steady state flow, the new methods are as fast as, or faster than DSMC using the standard VHS model. Unlike more complicated models with realistic viscosities, the new procedures are compatible with the Borgnakke-Larsen energy exchange scheme and the established chemistry models for DSMC. ©2005 American Institute of Physics 2005-02-25T00:00:00Z Macrossan, M. N. http://espace.library.uq.edu.au/view/UQ:183649 2009-09-04T00:00:00Z Liu, M. og Zanna, S. og Ardelean, H. og Frateur, I. og Schmutz, P. og Song, G.L. og Atrens, A. og Marcus, P. http://espace.library.uq.edu.au/view/UQ:130659 The choice of extended warranties (EWs) currently available to consumers is extremely limited. Their EW purchase decisions have to be made at or very close to the time that they purchase the products and, at this point, they are uncertain about item reliability, future operating costs, and usage time before replacement. In this paper, we discuss an EW that offers more flexibility and we investigate optimal pricing strategies for the EW provider and optimal maintenance and replacement strategies for the consumer. 2008-02-18T00:00:00Z Jack, N. og Murthy, D. N. P. http://espace.library.uq.edu.au/view/UQ:289802 This focused review includes two parts. In the first part, the previous studies on the deformations of monocrystalline Si induced by nanoscratching were summarised. In the second part, our recent studies on the scratching-induced deformation of Si were systematically presented. The studies have demonstrated that lateral force in nanoscratching plays a key role in the amorphization and phase transformation of Si under mechanical loading. The deformation route of Si appears to be different from those reported from the nanoindentation studies. 2013-01-25T07:39:16Z Wu, Yueqin og Huang, Han og Zou, Jin http://espace.library.uq.edu.au/view/UQ:186771 2009-11-17T00:00:00Z Huang, Tianyou og Wang, Gui og et al. http://espace.library.uq.edu.au/view/UQ:135355 2008-04-15T00:00:00Z Green, M. og Williams, I. og McAree, P. R. http://espace.library.uq.edu.au/view/UQ:8863 A free-piston driven shock tunnel, operating in the non-reflected mode, was used to obtain a strongly dissociating flow of pure nitrogen (Mach 5.66) over a blunt nosed body, 65 mm long. The flow speed is approximately 6 km/s and the Damkohler number of O(1) indicates that the flow is in chemical non-equilibrium. The useful test time is shorter than for conventional shock tunnel operation but the "prior-steady-flow" technique has been used to establish a fully developed flow. Interferograms of the afterbody flow have been made and compared with results obtained from a finite volume (kinetic theory based) CFD method the "Equilibrium Flux Method" for chemically reacting flows. The results show good agreement between experiments and computations. The experiments were perfomed in the T3 shock tunnel at the Australian National University. [For more details of the CFD method see M N Macrossan J Comput Physics v80, p204 1989. For more details of the flow and the experiments see M N Macrossan J Fluid Mechanics v207, p167 1990]. 2005-12-09T00:00:00Z Macrossan, Michael N. og Stalker, Ray J. http://espace.library.uq.edu.au/view/UQ:263858 2011-12-20T00:00:00Z Odabaee, Mostafa og Hooman, Kamel http://espace.library.uq.edu.au/view/UQ:101875 2007-08-23T00:00:00Z Dean, W. R. og Grandone, S. B. og Tadic, D. M. og Gledhill, M. E. og Qin, Z. http://espace.library.uq.edu.au/view/UQ:2829 2006-04-19T00:00:00Z Dean, W. R. og Grandone, S. og Tadic, D. og Gledhill, M. og Qin, J. http://espace.library.uq.edu.au/view/UQ:276158 Film embrittlement criteria were determined for photo-oxidative degradation of linear low density polyethylene (LLDPE) films by using a range of characterisation techniques: tensile, high-temperature GPC, MAS-NMR, FTIR-ATR, WAXS and SAXS. The key embrittlement criteria was the loss of 95% elongation at break and the reduction in interlamellar distance, reduced down to approximately 30–50 Å, as a result of recrystallisation of mobile short chain fragments produced from chain scission reaction. Interlamellar thinning correlated well with the changes in double yield points seen in the tensile data, where the absence of the second yield point signified that the tie molecules at the lamellar interface underwent chain scission and could no longer transfer the tensile stress to reach c-axis slip of the lamellar crystals. This was also supported by a reduction in amorphous–lamellar interfacial width with ageing time, extracted from SAXS data using the linear correlation function. 2012-06-25T09:36:05Z Hsu, Yu-Chieh og Weir, Michael P. og Truss, Rowan W. og Garvey, Christopher J. og Nicholson, Timothy M. og Halley, Peter J. http://espace.library.uq.edu.au/view/UQ:123345 The crystallography of fcc/bcc(bct) martensite transformation, including nucleation and growth, has been discussed from the viewpoint of invariant-line and O-lattice theory. The formation of martensite is accomplished by the immigration of well-defined glissile interface (121)(fcc) type and its misfit dislocations can produce the lattice invariant deformation (LID) on the basis of phenomenal theory of martensitic crystallography (PTMC), however, LID is retarded slightly after the migration of interphase (121)(fcc), i.e. a thin plate-like zone exists without LID in martensite near the well-defined interface. When the temperature reduces to the M-s point, the lattice parameter of austenite matrix is root 3/2 times that of the martensite without LID. This critical condition for spontaneous transformation agrees with that the stack fault energy in matrix is less than zero according to Olson and Cohen's nucleation model. 2008-01-25T00:00:00Z Yang, J. B. og Yang, Z. G. og Qiu, D. og Zhang, W. Z. og Zhang, C. og Bai, B. Z. og Fang, H. S. http://espace.library.uq.edu.au/view/UQ:178306 This paper follows the evolution in understanding of the multiple mapping conditioning (MMC) approach for turbulent combustion and reviews different implementations of MMC models. As the MMC name suggests, the original version represents a consistent combination of CMC-type conditional equations (conditional moment closure) and generalised mapping closure. It seems that the strength of the MMC model, and especially that of its stochastic version, lies in a more general (and much more transparent) interpretation. In this new generalised interpretation, we can replace complicated derivations by physical reasoning and the model appears to be a natural extension of modelling approaches developed in recent decades. MMC can be seen as a methodology for enforcing certain known characteristics of turbulence on a conventional mixing model. This is achieved by localising the mixing operation in a reference space. The reference space variables are selected to emulate the properties of a turbulent flow which have a strong effect on reactive quantities. The best and simplest example is an MMC model which has a single reference variable emulating the mixture fraction. In diffusion flames turbulent fluctuations of reacting quantities are strongly correlated with fluctuations of the mixture fraction. By making mixing local in the reference mixture fraction space a CMC-type mixing closure is enforced. In the original interpretation of MMC the reference variables are modelled as Markov processes. Since the reference variables should emulate properties of turbulent flows as realistically as possible the next step, and the basis of generalised MMC, is to remove the Markovian restriction and set reference variables equal to traced Lagrangian quantities within DNS or LES flow fields. Indeed, no Markov value can emulate the mixture fraction better than the mixture fraction itself. (Using a Markov vector process of dimension higher than the number of conditioning variables represents a more economical alternative for producing reference variables in generalised MMC.) The generalised MMC approach effectively incorporates the mixture fraction-based models, the PDF methods and LES/DNS techniques into a single methodology with possibility of blending useful features developed previously for conventional models. The generalised approach to MMC stimulates a more flexible understanding of simulations using sparsely placed Lagrangian particles as tools that may provide accurate joint distributions of reactive scalars at relatively low computational cost. The physical reasoning behind the new interpretation of MMC is supported by example computations for a partially premixed methane/air diffusion flame (Sandia Flame D). The scheme utilises LES for the dynamic field and a sparse-Lagrangian filtered density function method with MMC mixing for the scalar field. Two different particle mixing schemes are tested. Simulations are performed using only 35,000 Lagrangian particles (of these only 10,000 are chemically active) on a single workstation. The relatively low computational cost allows the use of realistic chemical kinetics containing 34 reactive species and 219 reactions. 2009-06-05T00:00:00Z Cleary, Matthew og Klimenko, Alexander Y. http://espace.library.uq.edu.au/view/UQ:97167 2007-08-24T00:00:00Z Inger, G. R. og Higgins, C. E. og Morgan, R. G. http://espace.library.uq.edu.au/view/UQ:198504 A hole in one: Hollow nanoporous structures are prepared by controlled decomposition-dissolution. The partial thermal decomposition of transition-metal salts forms a metal oxide shell on the surface of the metal salt particles. Acid washing removes the metal salt cores, resulting in hollow nanoporous metal oxide shells (see picture). This new strategy provides a template-free single-source route to hollow structures. 2010-03-10T00:00:00Z Wang, L. Z. og Tang, F. Q. og Ozawa, K. og Chen, Z. G. og Mukherj, A. og Zhu, Y. C. og Zou, J. og Cheng, H. M. og Lu, G. Q. http://espace.library.uq.edu.au/view/UQ:138275 Compared to a smooth channel, a finned-channel provides higher heat transfer coefficient and increasing the fin height enhances the heat transfer. However, this heat transfer enhancement is associated with an increase in the pressure drop. This leads to an increased pumping power requirement so that one may seek an optimum design for such systems. The main goal of this paper is to define the exact location and size of fins in such a way that a minimal pressure drop coincides with an optimal heat transfer based on the genetic algorithm. Each arrangement of fins is considered as a solution of the problem (an individual for genetic algorithm). An initial population is generated randomly at the first step. Then the algorithm has searched among these solutions and made new solutions iteratively by its functions to find an optimum design as reported in this article. 2008-05-13T00:00:00Z Mousavi, S. S. og Hooman, K. og Mousavi, S. J. http://espace.library.uq.edu.au/view/UQ:190594 Agglomeration and bending of equiaxed crystals were studied by microstructural characterization of specimens produced by near-static cooling, high-pressure die casting and Thixomolding®, where the solidifying crystals experience different levels of mechanical stresses. EBSD was used to acquire statistical grain misorientation data which is linked to crystal agglomeration and bending behavior during solidification. An aluminum alloy and two magnesium alloys were used to compare grain misorientations for different crystal structures. The length fraction of low-energy grain boundaries in HPDC and Thixomolded samples was substantially higher than in “statically cooled” samples. This is attributed to the high shear stresses and pressure applied on the solidifying alloy, which promote crystal collisions and agglomeration. In-grain misorientations were found to be significant only in branched dendritic crystals which were subjected to significant shear stresses. This is related to the increased bending moment acting on long, protruding dendrite arms compared to more compact crystal morphologies. 2009-12-20T00:00:00Z Otarawanna, S. og Gourlay, C. M. og Laukli, H. I. og Dahle, A. K. http://espace.library.uq.edu.au/view/UQ:138556 2008-05-15T00:00:00Z Ou, D.R. og Mori, T. og Ye, F. og Zou, J. og Drennan, J. http://espace.library.uq.edu.au/view/UQ:282641 This paper summarised our recent results on the development of grinding technologies for the fabrication of aspheric components at micro/meso scales made of cemented tungsten carbide. Based on these results, a grinding protocol was proposed for the fabrication of aspheric moulds. The protocol includes the understanding of deformation and removal mechanisms of hard and brittle materials involved in grinding, the preparation of grinding wheels, the compensation of profiling errors and the optimisation of the grinding process. 2012-10-01T19:59:42Z Huang, Han http://espace.library.uq.edu.au/view/UQ:147621 2008-06-06T00:00:00Z La Rosa, D. M. og Chitombo, G. P. http://espace.library.uq.edu.au/view/UQ:220696 2010-11-16T00:00:00Z Pierce, M. og Weatherley, D. K. og Kojovic, T. http://espace.library.uq.edu.au/view/UQ:217392 2010-09-29T00:00:00Z Palanisamy, S. og Nagarajah, C.R. og Graves, K. og Iovenitti, P. http://espace.library.uq.edu.au/view/UQ:274366 This paper presents 3D numerical simulation of an air-cooled metal foam heat exchanger with potential application in thermal management of fuel cell systems in general and Proton Exchange Membrane Fuel Cells, PEMFCs, in particular. It has been shown that the new design can lead to a uniform temperature distribution for the heated plate especially at higher air flow speeds. The heat transfer enhancement because of the foams leads to an increase in the pressure drop which is, interestingly, comparable to that of water-cooled PEMFCs. Other potential benefits of the application of metal foams for fuel cell thermal management are briefly discussed and estimated. 2012-05-21T22:20:58Z Boyd, Ben og Hooman, Kamel http://espace.library.uq.edu.au/view/UQ:293388 2013-03-11T12:28:34Z Creagh, Michael og Beasley, Peter og Dimitrijevic, Igor og Brown, Melrose og Tirtey, Sandy http://espace.library.uq.edu.au/view/UQ:139558 2008-06-10T00:00:00Z Dahle, A. K. og St John, D. H. http://espace.library.uq.edu.au/view/UQ:11392 The kinetic-theory-based solution methods for the Euler equations proposed by Pullin and Reitz are here extended to provide new finite volume numerical methods for the solution of the unsteady Navier-Stokes equations. Two approaches have been taken. In the first, the equilibrium interface method (EIM), the forward- and backward-flowing molecular fluxes between two cells are assumed to come into kinetic equilibrium at the interface between the cells. Once the resulting equilibrium states at all cell interfaces are known, the evaluation of the Navier-Stokes fluxes is straightforward. In the second method, standard kinetic theory is used to evaluate the artificial dissipation terms which appear in Pullin's Euler solver. These terms are subtracted from the fluxes and the Navier-Stokes dissipative fluxes are added in. The new methods have been tested in a 1D steady flow to yield a solution for the interior structure of a shock wave and in a 2D unsteady boundary layer flow. The 1D solutions are shown to be remarkably accurate for cell sizes large compared to the length scale of the gradients in the flow and to converge to the exact solutions as the cell size is decreased. The steady-state solutions obtained with EIM agree with those of other methods, yet require a considerably reduced computational effort. 2006-12-20T00:00:00Z Macrossan, M. N. og Oliver, R. I. http://espace.library.uq.edu.au/view/UQ:239022 Al-AlN composite powders were fabricated through nitriding aluminium powder mixtures of AA 6061-2%Mg-1%Sn-3%Nylon at 560 °C in nitrogen at atmospheric pressure. Each nitrided particle is enveloped by an in-situ formed AlN shell, which is a nanocomposite of Al-AlN, comprising nanoscale AlN whiskers and an Al matrix. The thickness of the ‘AlN shell’ increases with nitridation time, through which the AlN content can be readily controlled. The partially nitrided powders were consolidated using back pressure-assisted Equal Channel Angular Pressing (ECAP) at 200 °C, with a view to dispersing the nanoscale AlN. It was found that the processing behaviours of the Al-AlN composite powders were significantly affected by the AlN content. The ‘AlN shells’ were difficult to fragment as they deformed readily during ECAP. As a result, agglomeration or segregation of the AlN phase was observed after multi-passes of ECAP, particularly at large volume fractions. The attendant microstructures show shear banding and surface cracking when the AlN content is more than 20 vol.%. However, at a low volume fraction of AlN (8.9%), multi-passes of ECAP resulted in a dense Al-AlN microstructure with a reasonable dispersion of the AlN in the matrix. 2011-03-25T00:00:00Z Yu, Peng og Bettles, Colleen og Schaffer, G. B. og Qian, Ma http://espace.library.uq.edu.au/view/UQ:67375 2007-08-15T00:00:00Z Hall, BJ og Schaffer, GB og Ning, Z og McPhee, WAG og Miller, DN og Drennan, J og Cumming, DJ