Wyniki wyszukiwania - BazTech

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Theory of Red Blood Cell Oscillations in an Ultrasound Field

Johansen K., Kimmel E., Postema M.

Archives of Acoustics

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2017

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Vol. 42, No. 1

121--126

EN

Manipulating particles in the blood pool with noninvasive methods has been of great interest in therapeutic delivery. Recently, it was demonstrated experimentally that red blood cells can be forced to translate and accumulate in an ultrasound field. This acoustic response of the red blood cells has been attributed to sonophores, gas pockets that are formed under the influence of a sound field in the inner-membrane leaflets of biological cells. In this paper, we propose a simpler model: that of the compressible membrane. We derive the spatio-temporal cell dynamics for a spherically symmetric single cell, whilst regarding the cell bilayer membrane as two monolayer Newtonian viscous liquids, separated by a thin gas void. When applying the newly-derived equations to a red blood cell, it is observed that the void inside the bilayer expands to multiples of its original thickness, even at clinically safe acoustic pressure amplitudes. For causing permanent cell rupture during expansion, however, the acoustic pressure amplitudes needed would have to surpass the inertial cavitation threshold by a factor 10. Given the incompressibility of the inner monolayer, the radial oscillations of a cell are governed by the same set of equations as those of a forced antibubble. Evidently, these equations must hold for liposomes under sonication, as well.

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Lagrangian formalism for computing oscillations of spherically symmetric encapsulated acoustic antibubbles

Johansen K., Postema M.

Hydroacoustics

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2016

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Vol. 19

197--207

EN

Antibubbles are gas bubbles containing a liquid droplet core and, typically, a stabilising outer shell. It has been hypothesised that acoustically driven antibubbles can be used for active leakage detection from subsea production facilities. This paper treats the dynamics of spherically symmetric microscopic antibubbles, building on existing models of bubble dynamics. A more complete understanding of microbubble dynamics demands that the effects of the translational dynamics is included into the Rayleigh-Plesset equation, which has been the primary aim of this paper. Moreover, it is a goal of this paper to derive a theory that is not based on ad-hoc parameters due to the presence of a shell, but rather on material properties. To achieve a coupled set of differential equations describing the radial and translational dynamics of an antibubble, in this paper Lagrangian formalism is used, where a Rayleigh-Plesset-like equation allows for the shell to be modelled from first principles. Two shell models are adopted; one for a Newtonian fluid shell, and the other for a Maxwell fluid shell. In addition, a zero-thickness approximation of the encapsulation is presented for both models. The Newtonian fluid shell can be considered as a special case of the Maxwell fluid shell. The equations have been linearised and the natural and damped resonance frequencies have been presented for both shell models.

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Modelowanie oddziaływania pomiędzy kolejno odrywającymi się pęcherzami gazowymi

Mosdorf R., Wyszkowski T.

Modelowanie Inżynierskie

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2011

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T. 11, nr 42

269-274

PL

W pracy przedstawiono wyniki symulacji wzrostu pęcherza gazowego odrywającego się z cylindrycznej dyszy. Wzrost pęcherza opisano równaniem Rayleigha - Plesseta. Czas wzrostu pęcherza wyznaczano na podstawie położenia środka pęcherza ponad wylotem dyszy. W modelu uwzględniono: siłę wyporu, napięcia powierzchniowego, lepkości, inercji oraz strumień pędu gazu zasilającego pęcherz. Model pozwala na wyznaczenie czasu wzrostu pęcherza w funkcji prędkości cieczy otaczającej pęcherz wywołanej przez poprzednio odrywające się pęcherze. Wyniki symulacji porównano z wynikami badań eksperymentalnych, w których pęcherze powietrza wydostawały się z dyszy o średnicy wewnętrznej 1.1 mm. Ruch pęcherzy rejestrowano kamerą Casio EX FX1 z szybkością 1200 klatek na sek. Uzyskano dobrą ilościową zgodność wyników symulacji z wynikami eksperymentalnymi.

EN

In the paper the simulation of air bubble growth has been carried out. The bubble growth has been described using the Rayleigha - Plesseta equation. The time of the bubble growth has been calculated using the position of spherical bubble centre over the nozzle outlet. The following forces: buoyancy, surface tension, drag, Basset, added mass inertia and gas momentum flux have been considered. The time of the bubble growth as the function of liquid flow generated by previously departing bubble has been calculated. The simulation results have been compared with experimental measurement of the air bubble growth. In the experiment the bubbles have been generated from brass nozzle with inner diameter equal to 1.1 mm, submerged in distillated water. The bubble growth has been recorded using the high speed camera Casio EX FX1 (1200 fps). Good agreement between simulation results and experimental measurement has been obtained.