Developing an accurate non-Newtonian surface rheology model

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Being 'energy efficient' is something we have all come to better understand in recent times. As we continue to grapple with the cost-of-living crisis we have become ever familiar with the need to make energy-efficient decisions in the home. However, if we are to meet net-zero CO2 emissions targets we must think more globally about how to reduce the burning of fossil fuels. At present, one of the largest sources of CO2 emissions stems directly from the burning of fossil fuels for transportation purposes. Maritime transport alone emits around 1076 million tonnes of CO2 annually and is responsible for around 2.9% of global emissions caused by human activities. Indeed, in the United Nations 2023 Intercontinental Panel on Climate Change report, the authors note that "Rapid and far-reaching transitions across all sectors and systems are necessary to achieve deep and sustained emissions reductions and secure a liveable and sustainable future for all." One sector that contributes significantly to the production of greenhouse gases, via numerous different means, is the metallurgy industry. Whether this be through the burning of fossil fuels to produce the finished metallurgical products, or via the greenhouse gas costs associated with the continued travel of these materials across the globe, for example in the lifecycle of a steel-hulled cargo vessel. It is, therefore, imperative that we begin replacing dense and energy-inefficient materials such as steel, with functionalised energy-efficient light alloys.Molten aluminum alloys are widely utilised for the casting of lightweight parts that can be used to replace their traditional heavyweight counterparts. These high-strength alloys tend to oxidise very quickly when first exposed to air. A thin oxide film develops on the surface of the metal and this helps to protect the aluminium alloys against corrosion. However, the development of these thin films can be both a blessing and a curse. The film acts as a layer of protection from the outside elements which, under regular usage conditions, ensures the metal will not corrode. However, during the casting process, when the aluminum is still in a molten state, this thin oxide film can be encapsulated into the bulk of the liquid metal flow. It has been shown that this encapsulation process, which can happen many times over, necessarily leads to the embedding of these oxide films within the main body of the finished product. As a result of this process, the quality and fatigue life of the solidified cast parts can be greatly diminished. As such, gaining a better understanding of how to control this process plays a pivotal role in reducing the costs associated with the production lifecycle, thus resulting in an increased demand for the usage of lightweight alloys. These 'mass savings' then, in turn, contribute to the reduction of the generation of greenhouse gases. One needs to burn fewer fossil fuels moving a product from A to B given that the product is lighter than its traditional counterpart.The goal of the investigation will be to develop a mathematical model that is able to accurately describe the dynamics between the interface of the liquid metal flow and the oxide layer above. At present, the current state-of-the-art fails to capture this important behaviour. Our model will be validated and verified against current experimental observations and the results that stem from this study will provide new insights as to how this oxidization process can be controlled in a practical setting.