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- Karimi, Mohsen, 1983, et al.
(författare)
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Stochastic simulation of droplet breakup in turbulence
- 2020
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 380
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates single droplet breakup from a theoretical perspective and addresses whether breakup in turbulent flows can be studied using highly-resolved simulations. Transient and three-dimensional turbulent flow simulations are performed to investigate if the apparent stochastic outcome from the droplet breakup can be predicted. For a given turbulent dissipation rate the breakup events were simulated for various detailed turbulence realizations. For this purpose, a well-characterized system widely used for kernel development is utilized to validate the simulations with respect to the key characteristics of stochastic breakup, including droplet deformation time, the number of fragments, and the specific breakup rate. The statistical validations show very good agreement with all the quantitative properties relevant to the breakup dynamics. Necklace breakup is also observed in line with patterns found in experiments. Evidence is found that the rate of energy transfer is positively correlated with higher order fragmentation. This can allow development of more accurate breakup kernels compared to the ones that only relies on the maximum amount of energy transfer. It is concluded that the simulation method provides new data on the stochastic characteristics of breakup. The method also provides a means to extract more details than experimentally possible since the analysis allows better spatial and temporal resolutions, and 3D analysis of energy transfer which provides better accuracy compared to experimental 2D data.
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| 2. |
- Nasirimoghaddam, Samiramis, et al.
(författare)
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Assessment of pH-responsive nanoparticles performance on laboratory column flotation cell applying a real ore feed
- 2020
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Ingår i: International Journal of Mining Science and Technology. - : Elsevier BV. - 2095-2686. ; 30:2, s. 197-205
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles (NPs) can promote the column flotation process in mining industry. Nanoparticles’ effects on column flotation process (copper recovery, grade and flotation rate constant) are assessed in Sarcheshmeh Copper Complex, Iran, through response surface methodology (RSM) optimization technique. The γ-Al2O3, α-Fe2O3, SiO2, and TiO2 nanoparticles are selected for these experiments. A flotation rate constant is chosen as a response to assess the effect of nanoparticles on flotation in its kinetic sense. The process pH and nanoparticle dosage are selected as the influential parameters. Results obtained from RSM indicated that the maximum percentage of Cu recovery and grade is obtained at pH of 12 and nanoparticle dosage of 6 kg/t, through α-Fe2O3 and γ-Al2O3 nanoparticles, respectively. Applying nanoparticles in particular γ-Al2O3 and α-Fe2O3 increases the Cu recovery by 8–10% together with the grade by 3–6% in a significant manner. It is revealed that nanoparticles could effectively be applied in enhancing the flotation performance.
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| 3. |
- Oyegbile, Benjamin, et al.
(författare)
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Modelling the Dynamics of Granular Particle Interactions in a Vortex Reactor using a Coupled DPM-KTGF Model
- 2020
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Ingår i: South African Journal of Chemical Engineering. - : Elsevier BV. - 1026-9185. ; 34, s. 31-46
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a shear-driven two-phase particulate flow of monodispersed and polydispersed granular materials has been studied experimentally and numerically as a function of solids concentration and restitution coefficients for different operating speeds N (70 -130 rpm) in a lab-scale rotor-stator agglomeration reactor. A coupled computational fluid-particle dynamics (CFPD) model was developed consisting of a steady-state flow field of the continuous phase coupled to a transient particle tracking of the discrete phase. This was achieved via a one-way coupling between the continuous and the discrete phase by including the effect of drag, lift, pressure gradient, virtual mass forces, as well as granular collisional forces in describing the particle-particle, particle-wall and the fluid-particle interactions. The spatiotemporal evolution of the flow pattern, discrete phase properties, and influence of the operating conditions on the granular properties were characterized. The validation of the numerical model developed in this study was carried out based on the theoretical analysis of the rotor-stator flow and the PIV flow measurements. The results showed that the particle sizes were uniformly distributed within the reactor after steady-state conditions, while a small region of high particle concentration was observed near the rotor due to low vorticity and turbulent intensity around the region. In terms of the operating conditions, the restitution coefficients and the operating speeds do not have a significant influence on the granular properties apart from the small region around the shaft where there is a correlation between these parameters. The particle sizes, however, show a positive correlation with the granular properties. Also, a wider particle size distribution was observed axially towards the stator, which might be attributed to the pumping effect of the Batchelor flow in this direction. It was also concluded that the discrete phase velocity does not seem to vary significantly with the restitution coefficients. Furthermore, the vertical velocity and vorticity profiles give a reasonably good agreement between the CFPD model predictions and PIV measurements. The minor observed deviations were mainly due to some of the experimental limitations rather than the robustness of the CFPD model or the numerical code.
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