Brendan Florio

The production and emission of fugitive dust is a topic ofconcern that Concrush brought to the MISG, 2020. Concrushis recycled concrete manufacturing company in the Hunterregion of New South Wales. Concrush's operations producefugitive dust, fine particles that can escape the site. Fugitive dust can travel long distances from the site ofemission, and can have negative health impacts includingrespiratory illnesses. Presently, concrete recyclingfacilities are managed by the Environmental ProtectionAgency using guidelines initially developed for the coalindustry. Concrush seeks to understand the appropriatenessof these guidelines, and how they can reduce and managefugitive dust on their Teralba site. Mathematical modellingof dust emission and transport, together with a review ofsimilar processes in the literature, identified a number ofpractical options for Concrush to reduce their dustemissions. In addition, opportunities for improved datacollection are identified.

To predict the trajectory of projectiles such as bullets and mortar shells, we require knowledge of the acting forces, including drag. For the most part, the drag coefficient (which is dependent on the local Mach number) is well-understood for subsonic and supersonic velocities. However, there is often a rapid and unintuitive change in the drag behaviour near the speed of sound. The transonic behaviour of the projectiles is addressed in two major ways. First we explain the underlying physics of drag in the three major regimes. The appearance of shock waves alters the drag forces dramatically. In some situations, the physical models are simplified to directly obtain the drag coefficient profile. Then we tackle an inverse problem, where firing table data gives the drag coefficient profile. The drag profile obtained by both point-by-point optimisation and by parametrising a suitable family of functions. Finally, transonic data is difficult to obtain in wind-tunnel experiments, so based on our understanding of the physics, alternative experiments are suggested. This research was undertaken as part of the 2017 Mathematics in Industry Study Group (Adelaide) with industry partner, the Defence Science and Technology group.

Hot groundwater in sedimentary basins can provide geothermal energy for low-temperature direct heat use applications, such as heating swimming pools, heating/cooling of buildings, desalination and industrial pre-heating (Regenauer-Lieb and Horowitz, 2007). The economic viability of geothermal energy projects depends on the depth that must be drilled to reach the required temperature. Thus, a primary goal of geothermal exploration is to identify areas where the geothermal gradient is higher than normal, such that useful temperatures are attained at relatively shallow depth. Our knowledge of temperature in the subsurface comes primarily from temperature measurements in boreholes, which can be interpolated to create a 3D model of temperature distribution. Such models reveal spatial variations in the geothermal gradient, which have traditionally been interpreted in terms of variations in thermal conductivity and basal heat flow, assuming that conduction is the dominant mechanism of heat transport. However, heat transport in sedimentary basins is dominated by advection and/or convection in some areas. The combined effects of advection, convection and conduction cause the temperature gradient to vary laterally and with depth, such that temperature predictions based on extrapolation of shallow geothermal gradients to greater depths may be incorrect. In this study we use borehole temperature measurements in the Perth Basin (Western Australia) and the Cooper Basin (South Australia and Queensland) to reveal spatial variations in the geothermal gradient. We consider whether these patterns are consistent with convection or conduction and discuss the implications for geothermal energy in these basins.

The possibility of convective upwelling in the sedimentary Perth Basin, based on available data and simple models, was examined and its relative contribution to heat transport in a geothermal context assessed. The presence of such upwelling could greatly increase the viability of geothermal power extraction from the Basin. The onset of convection is determined by the Rayleigh number, which provides a measure for the balance between buoyancy driven upwelling and viscous resistance to flow. Being sedimentary, the porous aquifer system is layered and fractured so that the effects of anisotropy, especially that in permeability, need to be accounted for when determining the critical Rayleigh number. Variations in viscosity and the coefficient of thermal expansion also occur within the convection zone. Estimates were made for the relative size of the convective contribution to heat transport. The possibility of the surface detection of cellular convection and the effects of horizontal inflow into the convection zone were examined.