The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Fabian Denner - One of the best experts on this subject based on the ideXlab platform.
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Capillary waves with surface viscosity
Journal of Fluid Mechanics, 2018Co-Authors: Li Shen, Fabian Denner, Berend Van Wachem, Neal Morgan, Daniele DiniAbstract:Experiments over the last 50 years have suggested a tentative correlation between the surface (shear) viscosity and the stability of a foam or emulsion. We examine this link theoretically using small-amplitude capillary waves in the presence of a surfactant solution of dilute concentration, where the associated Marangoni and surface viscosity effects are modelled via the Boussinesq–Scriven formulation. The resulting integro-differential initial value problem is solved analytically, and surface viscosity is found to contribute an overall Damping effect to the amplitude of the capillary wave with varying degree depending on the length scale of the system. Numerically, we find that the Critical Damping wavelength increases for increasing surface concentration but the rate of increase remains different for both the surface viscosity and the Marangoni effect.
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marangoni effect on small amplitude capillary waves in viscous fluids
Physical Review E, 2017Co-Authors: Li Shen, Fabian Denner, Berend Van Wachem, Neal Morgan, Daniele DiniAbstract:We derive a general integro-differential equation for the transient behavior of small-amplitude capillary waves on the planar surface of a viscous fluid in the presence of the Marangoni effect. The equation is solved for an insoluble surfactant solution in concentration below the Critical micelle concentration undergoing convective-diffusive surface transport. The special case of a diffusion-driven surfactant is considered near the the Critical Damping wavelength. The Marangoni effect is shown to contribute to the overall Damping mechanism, and a first-order term correction to the Critical wavelength with respect to the surfactant concentration difference and the Schmidt number is proposed.
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Frequency dispersion of small-amplitude capillary waves in viscous fluids.
Physical Review E, 2016Co-Authors: Fabian DennerAbstract:This work presents a detailed study of the dispersion of capillary waves with small amplitude in viscous fluids using an analytically derived solution to the initial value problem of a small-amplitude capillary wave as well as direct numerical simulation. A rational parametrization for the dispersion of capillary waves in the underdamped regime is proposed, including predictions for the wave number of Critical Damping based on a harmonic-oscillator model. The scaling resulting from this parametrization leads to a self-similar solution of the frequency dispersion of capillary waves that covers the entire underdamped regime, which allows an accurate evaluation of the frequency at a given wave number, irrespective of the fluid properties. This similarity also reveals characteristic features of capillary waves, for instance that Critical Damping occurs when the characteristic time scales of dispersive and dissipative mechanisms are balanced. In addition, the presented results suggest that the widely adopted hydrodynamic theory for damped capillary waves does not accurately predict the dispersion when viscous Damping is significant, and an alternative definition of the Damping rate, which provides consistent accuracy in the underdamped regime, is presented.
Daniele Dini - One of the best experts on this subject based on the ideXlab platform.
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Capillary waves with surface viscosity
Journal of Fluid Mechanics, 2018Co-Authors: Li Shen, Fabian Denner, Berend Van Wachem, Neal Morgan, Daniele DiniAbstract:Experiments over the last 50 years have suggested a tentative correlation between the surface (shear) viscosity and the stability of a foam or emulsion. We examine this link theoretically using small-amplitude capillary waves in the presence of a surfactant solution of dilute concentration, where the associated Marangoni and surface viscosity effects are modelled via the Boussinesq–Scriven formulation. The resulting integro-differential initial value problem is solved analytically, and surface viscosity is found to contribute an overall Damping effect to the amplitude of the capillary wave with varying degree depending on the length scale of the system. Numerically, we find that the Critical Damping wavelength increases for increasing surface concentration but the rate of increase remains different for both the surface viscosity and the Marangoni effect.
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marangoni effect on small amplitude capillary waves in viscous fluids
Physical Review E, 2017Co-Authors: Li Shen, Fabian Denner, Berend Van Wachem, Neal Morgan, Daniele DiniAbstract:We derive a general integro-differential equation for the transient behavior of small-amplitude capillary waves on the planar surface of a viscous fluid in the presence of the Marangoni effect. The equation is solved for an insoluble surfactant solution in concentration below the Critical micelle concentration undergoing convective-diffusive surface transport. The special case of a diffusion-driven surfactant is considered near the the Critical Damping wavelength. The Marangoni effect is shown to contribute to the overall Damping mechanism, and a first-order term correction to the Critical wavelength with respect to the surfactant concentration difference and the Schmidt number is proposed.
Kazuo Inoue - One of the best experts on this subject based on the ideXlab platform.
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Critical Damping of structures with elastically supported visco elastic dampers
Earthquake Engineering & Structural Dynamics, 2002Co-Authors: Yujin Lee, Izuru Takewaki, Koji Uetani, Kazuo InoueAbstract:This paper presents a new formulation for Critical Damping of structures with elastically supported visco-elastic dampers.Owing to the great dependence of damper performance on the support stiffness, this model is inevitable for reliable modelling of structures with visco-elastic dampers. It is shown that the governing equation of free vibration of this model is reduced to a third-order differential equation and the conventional method for defining the Critical Damping for second-order differential equations cannot be applied to the present model. It is demonstrated that the region of overdamped vibration is finite in contrast to that (semi-infinite) for second-order differential equations and multiple Critical Damping coefficients exist. However, it turns out that the smaller one is practically meaningful. Copyright © 2001 John Wiley & Sons, Ltd.
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Critical Damping of structures with elastically supported visco‐elastic dampers
Earthquake Engineering & Structural Dynamics, 2001Co-Authors: Yujin Lee, Izuru Takewaki, Koji Uetani, Kazuo InoueAbstract:This paper presents a new formulation for Critical Damping of structures with elastically supported visco-elastic dampers.Owing to the great dependence of damper performance on the support stiffness, this model is inevitable for reliable modelling of structures with visco-elastic dampers. It is shown that the governing equation of free vibration of this model is reduced to a third-order differential equation and the conventional method for defining the Critical Damping for second-order differential equations cannot be applied to the present model. It is demonstrated that the region of overdamped vibration is finite in contrast to that (semi-infinite) for second-order differential equations and multiple Critical Damping coefficients exist. However, it turns out that the smaller one is practically meaningful. Copyright © 2001 John Wiley & Sons, Ltd.
Hiroko Arai - One of the best experts on this subject based on the ideXlab platform.
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Critical Damping constant of microwave assisted magnetization switching
Applied Physics Express, 2016Co-Authors: Toshiki Yamaji, Hiroko Arai, Rie Matsumoto, Hiroshi ImamuraAbstract:Microwave-assisted switching of magnetization in a perpendicularly magnetized disk was theoretically studied and special attention was paid to the effect of a Damping constant on the switching field. We found that there exists a Critical Damping constant above which the switching field suddenly increases. We derived an analytical expression of the Critical Damping constant and showed that it decreases with increasing frequency of the microwave field, while it increases with increasing amplitude of the microwave field and the effective anisotropy field.
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Critical Damping constant of a spin torque oscillator with a perpendicularly magnetized free layer and an in plane magnetized reference layer
Physical Review B, 2015Co-Authors: Hiroko Arai, Rie Matsumoto, Shinji Yuasa, Hiroshi ImamuraAbstract:We theoretically analyzed the effects of Damping on spin torque induced oscillation in a spin torque oscillator with a perpendicularly magnetized free layer and an in-plane magnetized reference layer. It was found that there exists an unexpectedly small Critical Damping constant, above which no steady-state oscillation can be excited by spin torque. It was also found that the Critical Damping constant is almost independent of the anisotropy constants but increases with the spin polarization of the injected current.
Hiroshi Imamura - One of the best experts on this subject based on the ideXlab platform.
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Critical Damping constant of microwave assisted magnetization switching
Applied Physics Express, 2016Co-Authors: Toshiki Yamaji, Hiroko Arai, Rie Matsumoto, Hiroshi ImamuraAbstract:Microwave-assisted switching of magnetization in a perpendicularly magnetized disk was theoretically studied and special attention was paid to the effect of a Damping constant on the switching field. We found that there exists a Critical Damping constant above which the switching field suddenly increases. We derived an analytical expression of the Critical Damping constant and showed that it decreases with increasing frequency of the microwave field, while it increases with increasing amplitude of the microwave field and the effective anisotropy field.
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Critical Damping constant of a spin torque oscillator with a perpendicularly magnetized free layer and an in plane magnetized reference layer
Physical Review B, 2015Co-Authors: Hiroko Arai, Rie Matsumoto, Shinji Yuasa, Hiroshi ImamuraAbstract:We theoretically analyzed the effects of Damping on spin torque induced oscillation in a spin torque oscillator with a perpendicularly magnetized free layer and an in-plane magnetized reference layer. It was found that there exists an unexpectedly small Critical Damping constant, above which no steady-state oscillation can be excited by spin torque. It was also found that the Critical Damping constant is almost independent of the anisotropy constants but increases with the spin polarization of the injected current.