The Influence of Ultrasound Irradiation on Falling Sphere in Pseudo-Plastic Fluid

Iwamuro, Minoru; Watamura, Tomoaki; Sugiyama, Kazuyasu

doi:10.3811/jjmf.2019.007

Cited by 2 publications

(4 citation statements)

References 14 publications

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“…The typical fluctuating velocity amplitude in Iwamuro et al. (2019) is estimated as m s, that is comparable to the fall speed . Hence, the dimensionless oscillation amplitude would be of order unity.…”

Section: Numerical Simulationmentioning

confidence: 90%

“…We choose the dimensionless angular frequency and oscillation amplitude by referring to experimental work using a spherical particle (Iwamuro et al. 2019). Considering the liquid density kgm, the sound pressure amplitude Pa, the frequency s and the speed of sound m s, the fluctuating acceleration amplitude is estimated as m s.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…The ratio of the fluctuating force amplitude to the time-averaged drag force would be (Δα * )/G ∼ 10 3 , which scales the dimensionless angular frequency ω. The typical fluctuating velocity amplitude in Iwamuro et al (2019) is estimated as…”

Section: Numerical Simulationmentioning

confidence: 99%

“…The pulsation, oscillation and acoustic excitation increase the speed of a bubble (Stein & Buggisch 2000;Iwata et al 2008;Karapetsas et al 2019), drop (Mendoza-Fuentes et al 2018) or particle (Iwamuro, Watamura & Sugiyama 2019), and significantly augment the rate of heat transfer in shear-thinning fluids (Gupta, Patel & Chhabra 2020Mishra, Patel & Chhabra 2020;Mishra & Chhabra 2021). Qualitatively, the cause is attributed to the reduction in the effective viscosity.…”

Section: Introductionmentioning

confidence: 99%

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Drag force on an oscillatory spherical bubble in shear‐thinning fluid

2023

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Power-law shear-thinning fluid motions induced by a translating spherical bubble with sinusoidal oscillation at a high frequency are numerically studied. We focus on reducing the time-averaged drag force $D$ on the bubble owing to the oscillation-enhanced shear-thinning effect. Under the assumption of negligible convection, the unsteady Stokes equation is directly solved in a finite-difference manner over a wide parameter space of the dimensionless oscillation amplitude $A$ (corresponding to the oscillatory-to-translational velocity ratio) and the power-law index $n$ of the viscosity. The results show that, for small amplitude ( $A\ll 1$ ), the drag reduction ratio $1-D/D_0$ (here, $D_0$ is $D$ with no oscillation) is proportional to $A^2$ . In contrast, for large amplitude ( $A \gg 1$ ), the drag ratio $D/D_0$ is proportional to $A^{n-1}$ , revealing a power-law behaviour. In the case of $A \gg 1$ for a strong shear-thinning fluid with small $n$ , the square of the vorticity over the entire domain is much smaller than that of the shear rate, and thus the bulk flow may be regarded as irrotational. To provide a fundamental perspective on the drag reduction mechanism, a theoretical model is proposed based on potential theory, and demonstrated to well capture the power-law relation between $D/D_0$ and $A$ .

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Section: Numerical Simulationmentioning

confidence: 90%

Section: Numerical Simulationmentioning

confidence: 99%

Section: Numerical Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Drag force on an oscillatory spherical bubble in shear‐thinning fluid

2023

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多相融体の流動特性評価とプロセスシミュレーション

Higuchi,

Shimasaki,

Ueda

et al. 2024

Tetsu-to-Hagane

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In the process of steelmaking refining, slag used in the preliminary treatment of molten iron or the converter is a multiphase melt. It contains solid particles that cannot dissolve entirely from the raw materials and gas bubbles generated through reactions, thus making it a multiphase molten material with dispersed components. The flow characteristics of the suspensions, foams, and emulsions significantly affect the separation of iron particles in the slag and the behavior of slag discharge. Multiphase melts typically behave as non-Newtonian fluids, so the evaluation, focusing on viscosity, is crucial to understanding their flow characteristics. This report reviews recent advances in slag visualization techniques for understanding the flow of multiphase molten materials. The results are as follows:Through studies of viscosity measurements of multiphase melts using rotational viscometers, falling-ball methods, and dam break methods in cold experiments with simulated slag and hightemperature experiments with slag compositions close to practical operation, it has been shown that the apparent viscosity increases with an increase in the volume fraction of solid particles and bubbles. The complex behaviors of the viscosity measurement values could have been reproduced with high precision using predictive models based on recent developments in machine learning. In terms of process evaluation, the application of mesh and mesh-free methods is advancing as methods of computational fluid dynamics (CFD) that take non-Newtonian behavior into account, providing valuable insights into evaluating slag discharge properties and more.

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The Influence of Ultrasound Irradiation on Falling Sphere in Pseudo-Plastic Fluid

Cited by 2 publications

References 14 publications

Drag force on an oscillatory spherical bubble in shear‐thinning fluid

Drag force on an oscillatory spherical bubble in shear‐thinning fluid

多相融体の流動特性評価とプロセスシミュレーション

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