Numerical Simulation and Investigation of System Parameters of Sonochemical Process

Chakma, Sankar; Moholkar, Vijayanand S.

doi:10.1155/2013/362682

Cited by 38 publications

(24 citation statements)

References 34 publications

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“…The first law of thermodynamics is employed for calculating the internal energy change inside the bubble (Toegel et al 2000;Samiei et al 2011;Chakma and Moholkar 2013)…”

Section: Temperature Change Of the Bubblementioning

confidence: 99%

Bubble dynamics in boiling histotripsy

Pahk

Gélat

Kim

et al. 2018

Ultrasound in Medicine & Biology

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Boiling histotripsy is a non-invasive, cavitation-based ultrasonic technique which uses a number of millisecond pulses to mechanically fractionate tissue. Though a number of studies have demonstrated the efficacy of boiling histotripsy for fractionation of solid tumours, treatment monitoring by cavitation measurement is not well studied because of the limited understanding of the dynamics of bubbles induced by boiling histotripsy. The main objectives of this work are to (a) extract qualitative and quantitative features of bubbles excited by shockwaves and (b) distinguish between the different types of cavitation activity for either a thermally or a mechanically induced lesion in the liver. A numerical bubble model based on the Gilmore equation accounting for heat and mass transfer (gas and water vapour) was developed to investigate the dynamics of a single bubble in tissue exposed to different High Intensity Focused Ultrasound fields as a function of temperature variation in the fluid. Furthermore, ex vivo liver experiments were performed with a passive cavitation detection system to obtain acoustic emissions. The numerical simulations showed that the asymmetry in a shockwave and water vapour transport are the key parameters which lead the bubble to undergo rectified growth at a boiling temperature of 100°C. The onset of rectified radial bubble motion manifested itself as (a) an increase in the radiated pressure and (b) the sudden appearance of higher order multiple harmonics in the corresponding spectrogram. Examining the frequency spectra produced by the thermal ablation and the boiling histotripsy exposures, it was observed that higher order multiple harmonics as well as higher levels of broadband emissions occurred during the boiling histotripsy insonation. These unique features in the emitted acoustic signals were consistent with the experimental measurements. These features can, therefore, be used to monitor (a) the different types of acoustic cavitation activity for either a thermal ablation or a mechanical fractionation process and (b) the onset of the formation of a boiling bubble at the focus in the course of HIFU exposure.

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“…The first law of thermodynamics is employed for calculating the internal energy change inside the bubble (Toegel et al 2000;Samiei et al 2011;Chakma and Moholkar 2013)…”

Section: Temperature Change Of the Bubblementioning

confidence: 99%

Bubble dynamics in boiling histotripsy

Pahk

Gélat

Kim

et al. 2018

Ultrasound in Medicine & Biology

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“…In order to understand such behaviour of a cavitation reactor, the apparent rate constant (which in reality is function of cavitation device configuration, operating conditions, number of passes through cavitation device and so on) is correlated with results obtained with cavity dynamics models. Extensive work on cavity dynamics models has been done by Pandit -Gogate -Moholkar and their co-workers (see for example, Gireesan and Pandit, 2017;Chakma and Moholkar, 2013;Sharma et al, 2008;Krishnan et al, 2006;Kanthale et al, 2005 and references cited therein. Krishnan et al (2006) developed the framework to predict OH generation from collapse conditions.…”

Section: Introductionmentioning

confidence: 99%

Modelling of vortex based hydrodynamic cavitation reactors

Sarvothaman

Simpson

Ranade

2019

Chemical Engineering Journal

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Vortex based hydrodynamic cavitation reactors offer various advantages like early inception, less erosion and higher cavitational yield. No systematic modelling efforts have been reported to interpret the cavitation performance of these vortex based devices for cavitation. It is essential to develop a modelling framework for describing performance of cavitation reactors. We have addressed this need in the present work. A comprehensive modelling framework comprising three layers: per-pass performance models (overall process), computational fluid dynamics models (flow on reactor scale) and cavity dynamics models (cavity scale) is developed. The approach and computational models were evaluated using the experimental data on treatment of acetone-contaminated water. The presented models were successful in describing the experimental data using initial cavity size as an adjustable parameter. Efforts were made to quantify optimum operating conditions and scale-up. The developed approach, models and results will provide useful design guidelines for pollutant degradation using vortex based cavitation reactors. It will also provide a sound and useful basis for comprehensive multiscale modelling of hydrodynamic cavitation reactors.

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“…increase the absorption of photons, is a well-known technique [15][16][17][18][19][20][21][22][23]. As the transition metal 20 ions are incorporated into the TiO 2 or ZnO lattice, impurity energy levels in the band gap of 21 where, M and M n+ represent the metal and metal ion dopant respectively.…”

Section: Introductionmentioning

confidence: 99%

Investigation in mechanistic issues of sonocatalysis and sonophotocatalysis using pure and doped photocatalysts

Chakma

Moholkar

2015

Ultrasonics Sonochemistry

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107

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This paper attempts to investigate the mechanistic issues of two hybrid advanced oxidation processes (HAOPs), viz. sonocatalysis and sonophotocatalysis, in which the two individual AOPs, viz. sonolysis and photocatalysis, are combined. Three photocatalysts, viz. pure ZnO and Fe-doped ZnO (with two protocols) have been employed. Fe-doped ZnO catalyst has been characterized using standard techniques. Decolorization of two textile dyes has been used as the model reaction. With experiments that alter the characteristics of ultrasound and cavitation phenomena in the medium, the exact synergy between the two AOPs has been determined using a quantitative yard stick. The results revealed a negative synergy between the two AOPs, which is an almost consistent result for decolorization of both dyes using all three photocatalysts. Fe-doping of ZnO catalyst helps in generation of more OH radicals that could augment decolorization. However, these radical mainly react with dye molecules adsorbed on catalyst surface. Intense shock waves generated by cavitation bubbles cause desorption of dye molecules from catalyst surface and reduce the probability of dye-radical interaction, thus reducing the net utility of photochemically generated OH radicals towards dye decolorization. This is rationale underlying the negative synergy between sonolysis and photocatalysis. Fe-doped ZnO catalyst increases the extent of decolorization, but the synergy between the two individual AOPs remains unaltered with doping.

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Numerical Simulation and Investigation of System Parameters of Sonochemical Process

Cited by 38 publications

References 34 publications

Bubble dynamics in boiling histotripsy

Bubble dynamics in boiling histotripsy

Modelling of vortex based hydrodynamic cavitation reactors

Investigation in mechanistic issues of sonocatalysis and sonophotocatalysis using pure and doped photocatalysts

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