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Siphonic roof drainage systems are finding increasing acceptance amongst architects and builders of large commercial buildings in Australia. The benefits of siphonic roof drainage over conventional roof drainage systems include underground excavation savings, higher flow volumes, fewer outlets and stormwater harvesting and reuse potential. Siphonic roof drainage systems are generally designed using the steady state Bernoulli and the Colebrook-White equations. Both of these equations assume a full bore flow regime which only occurs for short periods in siphonic systems. This means that the majority of storm events do not cause the system to run at its full capacity or efficiency. In Australia, systems are designed to cope with a maximum design rainfall intensity, usually the 1 in 100 year storm event. While the performance of siphonic roof drainage systems at this rainfall intensity is well understood, the system performance at lower rainfall intensities and unsteady flow regimes is largely unknown. This research aims to investigate and identify the improvements which can be effected to the overall performance of siphonic roof drainage by the removal of air from the system. The research will also investigate the effect the air entrainment has on siphonic flows. / PhD Doctorate

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The turbulen flow in an asymmetric diffuser has been en studied by the means of Reynold average Navier-Stokes equations with both differential and explict algebraic expressions to model the Reynolds stress tensor. Modifications to the differential stress model have been derived, using the inverse turbulence timescale to obtain the dissipation of turbuence kinetic energy. The explicit algebraic Reynolds stress model has been used in combination with a two-equation platform to close the system of equations. Modifications made to the transport equation for the inverse turbulence timescale has made it possible to substantially relax the deman on near-wall resolution of this quantity. The rapid growth wth present in the original formulation can be treated as an explicit function of the wall-normal distance. In order to use the new formulation for the transport equation, an equation has as been derived to obtain the shortest distance bettwee a point and the closest wall, regardles of the geometric complexity of the domain. An explicit algebraic expression to model the passive scalar flux vector has been investigated using a comparison with a standard eddy-diffusivity model in the asymmetric diffuser. Results show a substantial improvement of the complexity of the scalar field and scalar flux vector in sepaarated flows. Automated code generation has been used in all the above studies to generate versatile model testing tools for general two-dimensional geometries. Finite element formulations are used for these tools.

<p>The turbulen flow in an asymmetric diffuser has been en studied by the means of Reynold average Navier-Stokes equations with both differential and explict algebraic expressions to model the Reynolds stress tensor. Modifications to the differential stress model have been derived, using the inverse turbulence timescale to obtain the dissipation of turbuence kinetic energy. The explicit algebraic Reynolds stress model has been used in combination with a two-equation platform to close the system of equations. Modifications made to the transport equation for the inverse turbulence timescale has made it possible to substantially relax the deman on near-wall resolution of this quantity. The rapid growth wth present in the original formulation can be treated as an explicit function of the wall-normal distance. In order to use the new formulation for the transport equation, an equation has as been derived to obtain the shortest distance bettwee a point and the closest wall, regardles of the geometric complexity of the domain. An explicit algebraic expression to model the passive scalar flux vector has been investigated using a comparison with a standard eddy-diffusivity model in the asymmetric diffuser. Results show a substantial improvement of the complexity of the scalar field and scalar flux vector in sepaarated flows. Automated code generation has been used in all the above studies to generate versatile model testing tools for general two-dimensional geometries. Finite element formulations are used for these tools.</p>

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The Bayer process for the production of alumina (A1203) from bauxite involves a perennial gibbsite (y-Al(OH)3) precipitation step, relating to an inherently slow crystal growth from supersaturated sodium aluminate solutions (pregnant Bayer liquors). The kinetics and mechanisms involved in the transformation of the tetrahydroxo, Al(III)-containing species in solution into octahedrally-coordinated Al(OH)3 crystals in the presence of NA+ and excess of ions, are as yet not fully known. To gain further knowledge and better understanding of the nature of solution species, their specific interaction and participation in the gibbsite crystallization mechanisms, the role alkali ions play in the kinetic behaviour and mechanisms of nucleation, growth and aggregation/agglomeration from caustic aluminate solutions of industrial strength has been investigated.

The Bayer process for the production of alumina (A1203) from bauxite involves a perennial gibbsite (y-Al(OH)3) precipitation step, relating to an inherently slow crystal growth from supersaturated sodium aluminate solutions (pregnant Bayer liquors). The kinetics and mechanisms involved in the transformation of the tetrahydroxo, Al(III)-containing species in solution into octahedrally-coordinated Al(OH)3 crystals in the presence of NA+ and excess of ions, are as yet not fully known. To gain further knowledge and better understanding of the nature of solution species, their specific interaction and participation in the gibbsite crystallization mechanisms, the role alkali ions play in the kinetic behaviour and mechanisms of nucleation, growth and aggregation/agglomeration from caustic aluminate solutions of industrial strength has been investigated.

Context: Fluid-particle systems are seldom used in games, the apparent performance costs of simulating a fluid-particle system discourages the developer to implement a system of such. The processing power delivered by a modern GPU enables the developer to implement complex particle systems such as fluid-particle systems. Writing efficient fluid-particle systems is the key when striving for real-time fluid-particle simulations with good scalability. Objectives: This thesis ultimately tries to provide the reader with a well-performing and scalable fluid-particle system simulated in real-time using a great number of particles. The fluid-particle system implements two different fluid physics models for diversity and comparison purposes. The fluid-particle system will then be measured for each fluid physics model and provide results to educate the reader on how well the performance of a fluid-particle system might scale with the increase of active particles in the simulation. Finally, a performance comparison of the particle scalability is made by completely excluding the fluid physics calculations and simulate the particles using only gravity as an affecting force to be able to demonstrate how taxing the fluid physics calculations are on the GPU. Methods: The fluid-particle system has been run using different simulation scenarios, where each scenario is defined by the amount of particles being active and the dimensions of our fluid-particle simulation space. The performance results from each scenario has then been saved and put into a collection of results for a given simulation space. Results: The results presented demonstrate how well the fluid-particle system actually scales being run on a modern GPU. The system reached over a million particles while still running at an acceptable frame rate, for both of the fluid physics models. The results also shows that the performance is greatly reduced by simulating the particle system as a fluid-particle one, instead of only running it with gravity applied. Conclusions: With the results presented, we are able to conclude that fluid-particle systems scale well with the number of particles being active, while being run on a modern GPU. There are many optimizations to be done to be able to achieve a well-performing fluid-particle system, when developing fluid-particle system you should be wary of the many performance pitfalls that comes with it. / Vätskebaserade partikelsystem används sällan inom realtidsspel. Dessa system är väldigt prestandakrävande, till den grad att de avskräcker utvecklare från att implementera dem i sina realtidsspel. GPGPU ger utvecklare möjligheten att implementera komplexa partikelsystem, såsom vätskepartikelsystem, och simulera dessa system i realtid. Den här uppsatsen utforskar två olika fysikmodeller som kan användas för vätskesimulering, och sedan utförs det prestandamätningar under varierande omständigheter. Baserat på dessa prestandamätningar så kan slutsatser dras om hur skalbart ett vätskepartikelsystem är, alltså hur prestandan sjunker i förhållande till antalet partiklar i systemet. Slutsatser som dras efter att samtliga mätningar har utförts är att dessa system har en god skalbarhet, men att det finns många prestandafallgropar man måste se upp för när man utvecklar ett vätskepartikelsystem.