Abstract
Removing inclusions from the melt is an important task in metallurgy with critical impact on the quality of the final alloy. Processes employed with this purpose, such as flotation, crucially depend on the particle size. For small inclusions, the aggregation kinetics constitute the bottleneck and, hence, determine the efficiency of the entire process. If particles smaller than all flow scales are considered, the flow can locally be replaced by a plane shear flow. In this contribution, particle interactions in plane shear flow are investigated, computing the fully resolved hydrodynamics at finite Reynolds numbers, using a lattice Boltzmann method with an immersed boundary method. Investigations with various initial conditions, several shear values and several inclusion sizes are conducted to determine collision efficiencies. It is observed that although finite Reynolds hydrodynamics play a significant role in particle collision, statistical collision efficiency barely depends on the Reynolds number. Indeed, the particle size ratio is found to be the prevalent parameter. In a second step, modeled collision dynamics are applied to particles tracked in a fully resolved bubbly flow, and collision frequencies at larger flow scale are derived.
Highlights
With the aim of maintaining their competitiveness and their position, steelmaking companies face many challenges of which the cleanliness of steels is a predominant one, since the need and value of cleaner steels have both been increasing over recent decades
Using the Lattice Boltzmann Method (LBM) framework, collision cross sections were determined at various Reynolds numbers and particle size ratios
Both parameters modify the cross-section area, it appears that the particle size ratio has a much stronger impact on the collision efficiency than the Reynolds number
Summary
With the aim of maintaining their competitiveness and their position, steelmaking companies face many challenges of which the cleanliness of steels is a predominant one, since the need and value of cleaner steels have both been increasing over recent decades. [1] gave a complete review of the control of steel cleanliness and more recently [2] brought fundamentals concerning NMI and demonstrates that most of NMI have a detrimental influence on the mechanical properties. These negative effects depend on the number of the inclusions and on their size. The cleanliness of steel depends upon the control of the inclusion content and type and upon the elimination of inclusions larger than the critical size harmful to the product
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