A numerical method is presented to simulate bubble–particle interaction phenomena in particle-laden flows.The bubble surface is represented in an Eulerian framework by a volume-of-fluid(VOF)method,while particle moti...A numerical method is presented to simulate bubble–particle interaction phenomena in particle-laden flows.The bubble surface is represented in an Eulerian framework by a volume-of-fluid(VOF)method,while particle motions are predicted in a Lagrangian framework.Different frameworks for describing bubble surfaces and particles make it difficult to predict the exact locations of collisions between bubbles and particles.An effective bubble,defined as having a larger diameter than the actual bubble represented by the VOFmethod,is introduced to predict the collision locations.Once the collision locations are determined,the attachment of particles to the bubble surface is determined using a novel numerical algorithm based on collision/induction times.The proposed numerical method is validated through simulations of a rising bubble moving through a layer of particles.The validity of the collision detection algorithm is examined by comparing the collision probability predicted by the present numerical method with that predicted from a theoretical relationship based on bubble/particle diameters.The attachment probability predicted by the present algorithm is found to agree well with that of an experiment.展开更多
Turbulent flow, the transpor＇t of inclusions and bubbles, and inclusion removal by fluid flow, transport and by bubble flotation in the strand of the continuous slab caster are investigated using computational models...Turbulent flow, the transpor＇t of inclusions and bubbles, and inclusion removal by fluid flow, transport and by bubble flotation in the strand of the continuous slab caster are investigated using computational models, and validated through comparison with plant measurements of inclusions. Steady 3-D flow of steel in the liquid pool in the mold and upper strand is simulated with a finitedifference computational model using the standard k-εturbulence rondel. Trajectories of inclusions and bubhles tire calculated by integrating each local velocity, considering its drag and buoyancy forces, A ＂random walk＂ model is used to incorporate the effect of turbulent fluctuations on the particle motion. The attachment probability of inclusions on a bubble surface is investigated based on fundamental fluid flow simulations, incorporating the turbulent inclusion trajectory and sliding time of each individual inclusion along the bubble surface as a function of particle and bubble size. The chunge in inclusion distribution due to removal by bubble transport in the mold is calculated based on the computed attachment probability of inclusions on each bubble and the computed path length of the bubbles. The results indicate that 6%-10% inclusions are removed by fluid flow transport. 10% by bubble flotation, and 4% by entrapment to the submerged entry nozzle （SEN） walls. Smaller bubbles and larger inclusions have larger attachment probabilities. Smaller bubbles are more efficient for inclusion removal by bubble flotation, so Inng as they are not entrapped in the solidifying shell A larger gas flow rate favors inclusion removal by bubble flotation. The optimum bubble size should be 2-4mm.展开更多
基金supported by the National Research Foundation of Korea(NRF)under the Grant Numbers NRF-2021R1A2C2092146 and RS-2023-00282764.
文摘A numerical method is presented to simulate bubble–particle interaction phenomena in particle-laden flows.The bubble surface is represented in an Eulerian framework by a volume-of-fluid(VOF)method,while particle motions are predicted in a Lagrangian framework.Different frameworks for describing bubble surfaces and particles make it difficult to predict the exact locations of collisions between bubbles and particles.An effective bubble,defined as having a larger diameter than the actual bubble represented by the VOFmethod,is introduced to predict the collision locations.Once the collision locations are determined,the attachment of particles to the bubble surface is determined using a novel numerical algorithm based on collision/induction times.The proposed numerical method is validated through simulations of a rising bubble moving through a layer of particles.The validity of the collision detection algorithm is examined by comparing the collision probability predicted by the present numerical method with that predicted from a theoretical relationship based on bubble/particle diameters.The attachment probability predicted by the present algorithm is found to agree well with that of an experiment.
文摘Turbulent flow, the transpor＇t of inclusions and bubbles, and inclusion removal by fluid flow, transport and by bubble flotation in the strand of the continuous slab caster are investigated using computational models, and validated through comparison with plant measurements of inclusions. Steady 3-D flow of steel in the liquid pool in the mold and upper strand is simulated with a finitedifference computational model using the standard k-εturbulence rondel. Trajectories of inclusions and bubhles tire calculated by integrating each local velocity, considering its drag and buoyancy forces, A ＂random walk＂ model is used to incorporate the effect of turbulent fluctuations on the particle motion. The attachment probability of inclusions on a bubble surface is investigated based on fundamental fluid flow simulations, incorporating the turbulent inclusion trajectory and sliding time of each individual inclusion along the bubble surface as a function of particle and bubble size. The chunge in inclusion distribution due to removal by bubble transport in the mold is calculated based on the computed attachment probability of inclusions on each bubble and the computed path length of the bubbles. The results indicate that 6%-10% inclusions are removed by fluid flow transport. 10% by bubble flotation, and 4% by entrapment to the submerged entry nozzle （SEN） walls. Smaller bubbles and larger inclusions have larger attachment probabilities. Smaller bubbles are more efficient for inclusion removal by bubble flotation, so Inng as they are not entrapped in the solidifying shell A larger gas flow rate favors inclusion removal by bubble flotation. The optimum bubble size should be 2-4mm.
