Cavitation Energy Research Articles

Sono-chemical successive ionic layer adsorption and reaction for the synthesis of CdS quantum dots onto mesoporous TiO2 photoanodes

Aiming at high efficiency of quantum dot-sensitized solar cells (QDSCs) with CdS quantum dots (QDs)/mesoporous TiO2 (mp-TiO2) photoanodes, physical properties of CdS QDs/mp-TiO2 grown by sono-chemical successive ionic layer adsorption and reaction (SC-SILAR) process were studied. It is found that SC-SILAR process has less growth time and larger absorbance of CdS QDs besides a uniform penetration into mp-TiO2 films, compared with the conventional SILAR process. Experimental results show that SC-SILAR is an effective method for growing CdS QDs with high efficiency due to an extra sono-chemical energy of acoustic cavitation.

Mapping of cavitational activity in a pilot plant dyeing equipment

A large number of papers of the literature quote dyeing intensification based on the application of ultrasound (US) in the dyeing liquor. Mass transfer mechanisms are described and quantified, nevertheless these experimental results in general refer to small laboratory apparatuses with a capacity of a few hundred millilitres and extremely high volumetric energy intensity. With the strategy of overcoming the scale-up inaccuracy consequent to the technological application of ultrasounds, a dyeing pilot-plant prototype of suitable liquor capacity (about 40L) and properly simulating several liquor to textile hydraulic relationships was designed by including US transducers with different geometries.Optimal dyeing may be obtained by optimising the distance between transducer and textile material, the liquid height being a non-negligible operating parameter. Hence, mapping the cavitation energy in the machinery is expected to provide basic data on the intensity and distribution of the ultrasonic field in the aqueous liquor. A flat ultrasonic transducer (absorbed electrical power of 600W), equipped with eight devices emitting at 25kHz, was mounted horizontally at the equipment bottom.Considering industrial scale dyeing, liquor and textile substrate are reciprocally displaced to achieve a uniform colouration. In this technology a non uniform US field could affect the dyeing evenness to a large extent; hence, mapping the cavitation energy distribution in the machinery is expected to provide fundamental data and define optimal operating conditions. Local values of the cavitation intensity were recorded by using a carefully calibrated Ultrasonic Energy Meter, which is able to measure the power per unit surface generated by the cavitation implosion of bubbles. More than 200 measurements were recorded to define the map at each horizontal plane positioned at a different distance from the US transducer; tap water was heated at the same temperature used for dyeing tests (60°C). Different liquid flow rates were tested to investigate the effect of the hydrodynamics characterising the equipment.The mapping of the cavitation intensity in the pilot-plant machinery was performed to achieve with the following goals: (a) to evaluate the influence of turbulence on the cavitation intensity, and (b) to determine the optimal distance from the ultrasound device at which a fabric should be positioned, this parameter being a compromise between the cavitation intensity (higher next to the transducer) and the US field uniformity (achieved at some distance from this device).By carrying out dyeing tests of wool fabrics in the prototype unit, consistent results were confirmed by comparison with the mapping of cavitation intensity.

Ballistically equivalent aluminium targets and the effect of hole slenderness ratio on ductile plate perforation

The concept of ballistically equivalent metals for ductile plate perforation has been defined and demonstrated for five aluminium alloys. Heuristic derivation of a semi-empirical relation between specific cavitation energy sc and hole slenderness ratio h/D (the ratio between plate thickness h and projectile nose base diameter D which is also known as the normalized plate thickness) has exposed a logarithmic dependence which is verified by experimental data. A closed-form logarithmic expression for sc which takes into account the h/D effect has led to a closed-form formula for the ballistic limit. The expression for sc is based on the spherical cavitation yield stress YcS which serves as a scaling yield stress for strain-hardening (softening) response. It is found that ballistically equivalent metals should have practically the same values of YcS and elastic modulus. The perforation of aluminium targets by 7.62 mm APM2 bullets is discussed and vast amount of experimental data is used to validate the particular ballistic limit formula. Application of the closed-form model is also demonstrated with connection to the more general concept of ballistically equivalent targets. The h/D effect on perforation of multilayered targets is examined and it is found that for ductile plate perforation the ballistic limit of a monolithic target is higher than the ballistic limit of any combination of its air-gapped parts. Under the constraint of n air-gapped protective layers with total thickness h the minimum ballistic limit is obtained for n identical layers.

Evaluation of the effect of ultrasonic variables at locally ultrasonic field on yield of hesperidin from penggan (Citrus reticulata) peels

It has been reported that the maximum ultrasonic power depended on the distance of ultrasonic irradiation surface. Therefore, to confirm this point, an experiment for ultrasound-assisted extraction (UAE) of hesperidin from penggan peels at locally ultrasonic field was performed by response surface methodology (RSM). A three-level three-factor Box–Behnken design was applied to evaluate the effects of three independent variables including ultrasonic power, extraction time and temperature on the yields of hesperidin at high and low ultrasonic irradiation surface. The results showed that the coefficients of two mathematical-regression models by means of the second-order polynomial equation obtained at high and low ultrasonic irradiation surface was 0.9742 and 0.9745, respectively, thus indicating that quadratic polynomial model could be used to estimate the ultrasound-assisted extraction of hesperidin. By comparison of the ultrasonic irradiation surface influence, the yield of hesperidin obtained at low ultrasonic irradiation surface was much higher than the high ultrasonic irradiation surface. Moreover, the scanning electron microscopy (SEM) showed that the particles' microstructures of Penggan peel obtained at low ultrasonic irradiation surface were destroyed more heavily than high ultrasonic irradiation surface. As a result, the vicinity of ultrasonic irradiation surface can generate stronger cavitation energy.

Enhanced-cavitation heating protocols in focused ultrasound surgery with broadband split-focus approach

A novel approach combining dual frequency and split focus approaches is proposed to substantially enhance heating in treatment by using a prototype broadband splitfocus transducer. Using a dual-frequency mode in which the higher frequency is twice the lower frequency, the superimposition of two frequency pressures in the confocal region can enhance nucleation cavitation and inertial cavitation activity. Ex vivo liver or gel phantom experiments using the dual frequencies of 1.2 and 2.4 MHz confirmed a lesion size about two times larger than that obtained using a single 1.6 MHz frequency. The mean square indicating inertial cavitation energy from filtered passive cavitation detection (PCD) data demonstrated that the inertial cavitation activity dominated the enhanced heating rate and that the extra frequency components in the dual-frequency case contributed to increasing the lesion size. The dual-frequency, split-focus protocol takes great advantages of temporally and spatially enhanced-cavitation heating. The results revealed that the dual-frequency, split-focus method enhanced the heating rate one order of magnitude more than other methods. The inertial cavitation energy waveform revealed that the strong inertial cavitation action was involved in enhanced heating in the entire 22 s treatment. The greater spatial area of preformed bubble-layer surface reflection (or scatter ultrasound) regime in the dual-frequency, split-focus protocol enhanced the proximal acoustic field and enlarged the enhanced-pressure field toward the transducer about 3 times in the axial original-focal dimension, as well as laterally. This regime supported the sustained inertial cavitation during a 22 s treatment. An increased pulse-repetition frequency (PRF) protocol was formed using dual frequency and split focus, increasing PRF from 1 to 10, 20, and 40 Hz to take advantage of pulse-induced cavitation. The experiments demonstrated that the lesion size with 20 Hz PRF was about 2.5 times that obtained with 1 Hz PRF, and possessed quick 0.2 s lesioninception time. Within the high-frequency band, the inertialcavitation frequency integral was approximately proportional to the lesion size of 1, 10, 20, and 40 Hz PRF respectively, indicating higher frequency contribution to enhanced heating.

Application of model of calendar planning for project management in building

Our results show that the amount of agglomerates of microorganisms decreases during the sonication and the concentration of individual microorganisms in suspension increases proportionally to the sonication time, the radius of colonies of cellular microorganisms decreases. Concentration of microorganism colonies increases linearly with time. This allows to calculate the rate of colonies decomposition into smaller. The total surface of the particles, participating in the aggregate formation is proportional to the aggregate concentration in the system and the surface, involved in the bonds between the particles in a single aggregate. Cavitation energy is spent on the destruction of bonds between particles in the aggregate, which is obviously proportional to the surface of surface segments of individual cells, connecting them with the neighbors in the colony. The reaction order on the aggregate concentration in the system is different from the first one. We have proposed an equation, which describes the destruction process of cell colonies of microorganisms under the influence of ultrasound.

Investigation of kinetics conformities with a law of decomposition of agglomerates of microorganisms in the condition of acoustic cavitation

Our results show that the amount of agglomerates of microorganisms decreases during the sonication and the concentration of individual microorganisms in suspension increases proportionally to the sonication time, the radius of colonies of cellular microorganisms decreases. Concentration of microorganism colonies increases linearly with time. This allows to calculate the rate of colonies decomposition into smaller. The total surface of the particles, participating in the aggregate formation is proportional to the aggregate concentration in the system and the surface, involved in the bonds between the particles in a single aggregate. Cavitation energy is spent on the destruction of bonds between particles in the aggregate, which is obviously proportional to the surface of surface segments of individual cells, connecting them with the neighbors in the colony. The reaction order on the aggregate concentration in the system is different from the first one. We have proposed an equation, which describes the destruction process of cell colonies of microorganisms under the influence of ultrasound.

The effect of adiabatic thermal softening on specific cavitation energy and ductile plate perforation

The effect of adiabatic thermal softening on specific cavitation energy of metals is analytically investigated with respect to ballistic limit predictions. Explicit stress-plastic strain relation that includes strain hardening response, thermal softening effect and constant strain rate sensitivity is obtained from Johnson–Cook integral equation under adiabatic conditions and an analogous stress-strain relation is suggested for the Ludwik hardening model. Extensions of these two adiabatic curves for an arbitrary strain hardening response are derived from generalized integral equations and an example for the Voce hardening model is demonstrated. Adiabatic thermal softening is found to be governed by an exponential decay which is controlled by two nondimensional softening parameters and the strain hardening effect while increase of yield stress by a constant strain rate response leads to an increase of the thermal softening effect. Decrease of spherical and cylindrical, plane-strain and plane-stress, specific cavitation energies due to adiabatic thermal softening is quantified for several aluminium and Weldox steel alloys and reveals an effect of 2–21% with the greatest impact on aluminium 7075-T651 plates under plane-stress conditions. This effect is reduced by a factor of two in ballistic limit predictions but is intensified in estimations of low residual velocities via striking velocities that are close to the ballistic limit. Comparison of theory predictions with simulation results and experimental data for several aluminium and Weldox steel alloys demonstrates the validity of the present analytical model.

Parametrization of the solvent action on modern artists' paint systems

A solvent action parametrization scheme has been developed combining relevant parameters of the solvent action on modern artists' paints to characterize the solvation and dissolving properties of different binding media. The new system combines different concepts used in solvent chemistry. It is based on the normalized and solute-dependent dimension [hδH + eET(30)cv]N. It comprises a polarity value ET(30)cv as the magnitude of the enthalpy, and a combined value representing the cavitation energy δH as an entropy-influencing factor. Forty-eight solvents were divided into five subgroups based on their interaction and structural properties. This binary scheme permits to reliably quantify spaces of efficiency. The graphical selectivity of the scheme was applied to four binding media systems (oil, alkyd, acrylic-, and acrylic-polystyrene) by determination of the swelling capacity of 48 solvents. The graphical visualization of the systematic parametrization of solvents permits one to judge the intermolecular interaction and other effects of solvation relevant to the restoration of painted artwork.

Fundamental solutions of cavitation in porous solids: a comparative study

The expansion of internally pressurized cavities, embedded in infinite bodies, in spherical and cylindrical (plane strain and plane stress) configurations, is investigated within the framework of finite plasticity. Material response is modeled by the Gurson theory for porous solids and includes strain hardening. Numerical results, obtained under the assumption of nearly universal loading histories, reveal limit cavitation states for all three deformation patterns. Cavitation is identified with asymptotic levels of the specific cavitation energy, which is highest for the spherical cavity and smallest for plane stress (plate) holes. The influence of material porosity is assessed in context of weight optimization of protective plates. A limited comparison with experimental data for porous titanium plate perforation reveals close prediction of ballistic limit velocity.

Quantification of cell death due to ultrasound therapy with both traditional and nested microbubbles

This work is a quantitative, in vitro investigation of cell death caused by ultrasound (US) therapy with two microbubble formulations, one typical and one nested in the aqueous core of a polymer microcapsule. In the case of un-nested mircobubbles, no cell death was observed below the inertial cavitation threshold, but cell death increased with increasing microbubble concentration and with peak negative ultrasound pressure at pressures exceeding the inertial cavitation threshold. Little to no cell death was observed with nested microbubbles, irrespective of the occurrence of inertial cavitation. We attribute the increased cell viability both to an increase in the inertial cavitation threshold and to absorbance of the energy of inertial cavitation by the outer PLA shell. Nested microbubbles can thus be considered safer than traditional, un-nested contrast agents for imaging without sacrificing the quality of the image.

A Simple Road for the Transformation of Few-Layer Graphene into MWNTs

We report the direct formation of multiwalled carbon nanotubes (MWNT) by ultrasonication of graphite in dimethylformamide (DMF) upon addition of ferrocene aldehyde (Fc-CHO). The tubular structures appear exclusively at the edges of graphene layers and contain Fe clusters. Fc in conjunction with benzyl aldehyde, or other Fc derivatives, does not induce formation of NT. Higher amounts of Fc-CHO added to the dispersion do not increase significantly MWNT formation. Increasing the temperature reduces the amount of formation of MWNTs and shows the key role of ultrasound-induced cavitation energy. It is concluded that Fc-CHO first reduces the concentration of radical reactive species that slice graphene into small moieties, localizes itself at the edges of graphene, templates the rolling up of a sheet to form a nanoscroll, where it remains trapped, and finally accepts and donates unpaired electron to the graphene edges and converts the less stable scroll into a MWNT. This new methodology matches the long held notion that CNTs are rolled up graphene layers. The proposed mechanism is general and will lead to control the production of carbon nanostructures by simple ultrasonication treatments.

Bubble Structures Between Two Walls in Ultrasonic Cavitation Erosion

The cavitation bubble structures for the stationary specimen method were clarified for various distances, h, between the stationary specimen and the horn-tip surface. The generated cavitation bubbles constituted a huge number of tiny bubbles and bubble clusters of different sizes. The maximum cluster size was 1.4 mm. The observed cavitation patterns systematically changed during tests from the subcavitating state to the supercavitating state with respect to the separation distance, h. For h <4 mm, the bubbles have a definite trajectory, and the pressure patterns manifest a circular shape as a result of streaming induced by ultrasonic cavitation. The feature morphology of the eroded surfaces revealed that the predominant failure mode was fatigue. In the light of the material failure features and the cavitation patterns, it is also deduced that the important mechanism to transfer the cavitation energy to the solid is shock pressures accompanied by collapsing clusters.

Evaluation of the mechanisms of the effect of ultrasound on Microcystis aeruginosa at different ultrasonic frequencies

Blooms of cyanobacteria are now considered to be a common environmental issue. They are hazardous to both domestic and wild animals and humans. Current treatments are unable to effectively control such blooms as they become tolerant to biocides and it is difficult to degrade cyanobacterial toxins in water. Alternative methods for control are currently under investigation. One potential effective method is ultrasonic irradiation. Ultrasound inactivates algal and cyanobacteria cells through cavitation by generating extreme conditions, resulting in a number of physical, mechanical and chemical effects. The aim of this study was to investigate the effect of ultrasound at different frequencies on Microcystis aeruginosa. Flow cytometry was used to measure cyanobacterial metabolic cell viability in addition to the more commonly used haemocytometry, optical density and fluorimetry. Results indicate low frequency 20 kHz ultrasound with high intensity (0.0403 W cm−3) is effective for the inactivation of cyanobacterial cells. Higher frequencies of 580 kHz (0.0041 W cm−3) also resulted in an inactivation effect, but 1146 kHz (0.0018 W cm−3) showed a declumping effect as evidenced by flow cytometry. Ultrasonic treatment over time under different sonication conditions demonstrates the following:1. Acoustic cavitation via mechanical effects can induce sufficient shear forces to directly rupture cyanobacteria cells.2. At higher ultrasonic frequencies the mechanical energy of cavitation is less but a larger proportion of free radicals are produced from the ultrasonic degradation of water, which chemically attacks and weakens the cyanobacteria cell walls.3. At higher frequencies free radicals also damage chlorophyll a leading to a loss in photosynthetic cell viability.4. At low powers ultrasonic energy results in declumping of cyanobacteria.

The CFD Analysis of Twin Flapper -nozzle Valve in Pure Water Hydraulic

Based on aqueous medium with low viscosity, poor lubrication, high vapor pressure and corrosion, and other special physical, chemical properties, this paper analyzed the pure water flow through the valve port, the cavitation corrosion, spiral vortex, energy loss, temperature rise and other issues may occur near the entrance. Flow field model has been established by the SolidWorks software. And the internal flow field in visual simulation analysis has been done through the FLUENT software. The pressure, speed, temperature, turbulent kinetic energy cloud pictures have been obtained, the analytical results has been validated. Meanwhile it prepared for structure optimization of pilot valve.

Comparison of calorimetric energy and cavitation energy for the removal of bisphenol-A: The effects of frequency and liquid height

For decades, the measurement of heat generated during sonication – the calorimetric method – has been considered to represent the energy efficiency of ultrasonic reactors for useful chemical reactions. In this study, a modified calorimetric energy method using cavitating and non-cavitating solutions, referred to as cavitation energy method, has been developed and compared with conventional calorimetric method for the removal of an organic pollutant, bisphenol-A, in aqueous solutions under various experimental conditions. As the liquid height/volume was increased, cavitation yield for the degradation and mineralization of BPA significantly increased at 36kHz and 262kHz. Higher cavitation yields were obtained for both degradation and mineralization at 262kHz compared to 36kHz. It was found that the cavitation energy had a better correlation with the degradation and mineralization of BPA compared to the calorimetric energy. The enhancement observed at higher liquid height has been suggested to be due to the establishment of a standing wave field. The cavitation energy method seems to be useful to design the sonochemical reactors for the removal aqueous pollutants.

On the efficiency of cavitation action on the process of the starch size preparation for the textile industry

The efficiency was evaluated of the bifrequency ultrasonic (US) cavitation action on the process of the preparation of starch sizes for cotton yarns. The application of the ultrasonic energy of bifrequency cavitation provides the possibility to prepare sizes without chemical reagents for the starch splitting and to cook the sizes at a lower temperature of about 85°C. The proposed method allows one to prepare sizes without high vapor pressures, to considerably reduce the time of the size preparation, and to decrease the consumption of food stuffs (the starch by up to 30% and vegetable oil by up to 50%).

Inhibitory effect of ultrasound on barnacle ( Amphibalanus amphitrite) cyprid settlement

The inhibitory effect of ultrasound on barnacle ( Amphibalanus amphitrite) cyprid was investigated under three excitation frequencies (23, 63, and 102 kHz). The linear regression models were built to study the effect of ultrasound pressure and exposure time on the cyprid settlement. The negative slopes of the linear regression lines indicate reduced settlement behavior with increased exposure time and acoustic pressure. The excitation frequency of 23 kHz was found to be the most effective on settlement inhibition, with 63 and 102 kHz exhibiting similar but weaker response. Separately, ultrasonic cavitation was investigated and confirmed in the filtered seawater (FSW) and partially degassed filtered seawater (PDFSW) via the acoustic spectrum analysis. The cavitation energy was found to be double in FSW than in PDFSW at 23 kHz with the acoustic pressure of 20 kPa. The much higher settlement reduction and stronger cavitation in FSW at 23 kHz suggest that cavitation is a possible if not most likely mechanism for the cyprid inhibition. The cavitation induced force may lead to physical damage to the cyprids which subsequently will result in much higher mortality. The cavitation effect was proven to be stronger at 23 kHz than the other two frequencies with the same acoustic energy, which might explain the enhanced efficiency on settlement reduction at this frequency.

Physical features of ultrasound assisted enzymatic degradation of recalcitrant organic pollutants

This work has attempted to provide answer to the interaction of sonolysis and enzymatic treatment on degradation of recalcitrant dyes in a combined treatment. The model system comprises of two dyes, acid red and malachite green as model pollutants, along with horseradish peroxidase as a model enzyme and ultrasound of 20 kHz frequency. A dual approach of coupling experimental results with simulations of cavitation bubble dynamics has been adopted. Utilization of oxidation potential of horseradish peroxidase has been found to be a function of convection level in the medium. Cavitation phenomenon is found to have an adverse effect on enzyme action due to generation of high amplitude shock waves, which denature the enzyme. Degradation of dye at high static pressure increases due to absence of cavitation and high energy interaction (or collisions) between enzyme and dye molecules, which are beneficial towards enzymatic oxidation of the latter. High intensity convection generated by ultrasound also obviates need for an external shielding agent such as PEG that prevents attachment of the phenoxy radicals to enzyme that blocks the active sites of the enzyme.

Molecular orientations at interfaces by extended polarizable continuum model

This study presents an investigation into orientation of molecular solutes at the interface of liquid water and other media. The calculation of electrostatic free energy of molecular solute is based on an extension of the polarizable continuum model (PCM) to interfacial system. The extended PCM computational scheme is incorporated with the self-consistent field procedure which is necessary to obtain more accurate electrostatic free energy and charge density distribution. The computation of non-electrostatic energy for interfacial system is also realized. Applying the numerical procedure to molecular systems, N,N′-diethyl-p-nitroaniline (DEPNA) at air/water interface and p-nitrophenol (PNP) at cyclohexane/water interface, the average orientational angles are in reasonable agreement with the experimental results. Taking both the electrostatic and the non-electrostatic energies into account, the analysis on the energy profiles shows that the electrostatic solvation energy is the dominant factor in determining the orientation angle for PNP, whereas for DEPNA, the orientation angle mainly depends on the cavitation energy. This suggests that, in addition to the electrostatic energy, taking the cavitation energy into account may provide a more complete view when we survey the molecular orientation at interface. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011