Development of an ultrasonic resonator for ballast water disinfection

Ultrasonic disinfection involves the application of low-frequency acoustic energy in a water body to induce cavitation. The implosion of cavitation bubbles generates high speed microjets >1 km/s, intense shock wave >1 GPa, localized hot spots >1000 K, and free-radicals, resulting in cell rupture and death of micro-organisms and pathogens. Treatment of marine ballast water using power ultrasonic is an energy-intensive process. Compared with other physical treatment methods such as ultraviolet disinfection, ultrasonic disinfection require 2 to 3 orders of magnitude more energy to achieve similar rate of micro-organism mortality. Current technology limits the amount of acoustic energy that can be transferred per unit volume of fluid and presents challenges when it comes to high-flow applications. Significant advancements in ultrasonic processing technology are needed before ultrasound can be recognized as a viable alternative disinfection method. The ultrasonic resonator has been identified as one of the areas of improvement that can potentially contribute to the overall performance of an ultrasonic disinfection system. The present study focuses on the design of multiple-orifice resonators (MOR) for generating a well-distributed cavitation field. Results show that the MOR resonator offers significantly larger vibrational surface area to mass ratio. In addition, acoustic pressure measurements indicate that the MOR resonators are able of distributing the acoustic energy across a larger surface area, while generating 2-4 times higher pressures than existing ultrasonic probes

Ultrasonic disinfection using large area compact radial mode resonators

Ultrasonic water treatment is based on the ability of an ultrasonic device to induce cavitation in the liquid, generating physical and chemical effects that can be used for biological inactivation. Effective treatment requires the ultrasonic device to generate intense cavitation field in a large treatment volume. Most conventional ultrasonic radiators fulfil only the first of these two requirements, rendering such devices highly unsuitable for use in high-volume, high-flow liquid processes. The present research investigates the design and performance of a new type of radial resonator in terms of their electromechanical characteristics, nonlinear behaviour, and their ability to treat synthetic ballast water with lower power consumption and short treatment times. The radial resonators were designed using finite element (FE) modelling, and the best designs related to their predicted modal behaviour and vibration uniformity were selected for fabrication and experimental evaluation. Experimental modal analysis (EMA) of the radial resonators showed excellent correlation with the FE models, deviating by only 0.3% at the tuned mode. Impedance analysis showed that the mechanical quality factor of the radial resonators are 28–165% higher than the commercial high-gain probe, but their coupling coefficients are 40–45% lower. Harmonic response characterisation (HRC) revealed shifts in the resonance frequencies at elevated excitation voltages. Duffing-like behaviour were observed in all resonators. RP-1 exhibited the Duffing-like behaviour to a far greater extent compared to the RPS-16 and RPST-16 multiple orifice resonators, indicating the influence of geometric parameters on the overall stiffness of the structure. Finally, experiments with Artemia nauplii and Daphnia sp. showed excellent biological inactivation capability of the radial resonators. Comparison with previous studies showed that 90% reduction in Artemia nauplii can be achieved with up to 33% less energy and using just one radial resonator compared to the dozens of conventional resonators used in precedent investigations. The present research have successfully demonstrated the use of FE modeling, EMA, and HRC to develop, validate, and characterise a new type of radial resonator. Experimental analysis showed that the radial resonators exhibited promising electrical, mechanical, and acoustical characteristics that has the potential to be cost-efficient, scalable, and a viable alternative water treatment method

Ultrasonic disinfection using large area compact radial mode resonators

Ultrasonic water treatment is based on the ability of an ultrasonic device to induce cavitation in the liquid, generating physical and chemical effects that can be used for biological inactivation. Effective treatment requires the ultrasonic device to generate intense cavitation field in a large treatment volume. Most conventional ultrasonic radiators fulfil only the first of these two requirements, rendering such devices highly unsuitable for use in high-volume, high-flow liquid processes. The present research investigates the design and performance of a new type of radial resonator in terms of their electromechanical characteristics, nonlinear behaviour, and their ability to treat synthetic ballast water with lower power consumption and short treatment times. The radial resonators were designed using finite element (FE) modelling, and the best designs related to their predicted modal behaviour and vibration uniformity were selected for fabrication and experimental evaluation. Experimental modal analysis (EMA) of the radial resonators showed excellent correlation with the FE models, deviating by only 0.3% at the tuned mode. Impedance analysis showed that the mechanical quality factor of the radial resonators are 28–165% higher than the commercial high-gain probe, but their coupling coefficients are 40–45% lower. Harmonic response characterisation (HRC) revealed shifts in the resonance frequencies at elevated excitation voltages. Duffing-like behaviour were observed in all resonators. RP-1 exhibited the Duffing-like behaviour to a far greater extent compared to the RPS-16 and RPST-16 multiple orifice resonators, indicating the influence of geometric parameters on the overall stiffness of the structure. Finally, experiments with Artemia nauplii and Daphnia sp. showed excellent biological inactivation capability of the radial resonators. Comparison with previous studies showed that 90% reduction in Artemia nauplii can be achieved with up to 33% less energy and using just one radial resonator compared to the dozens of conventional resonators used in precedent investigations. The present research have successfully demonstrated the use of FE modeling, EMA, and HRC to develop, validate, and characterise a new type of radial resonator. Experimental analysis showed that the radial resonators exhibited promising electrical, mechanical, and acoustical characteristics that has the potential to be cost-efficient, scalable, and a viable alternative water treatment method

Granular Flow and Heat Transfer in a Screw Conveyor Heater: A Discrete Element Modeling Study

Master'sMASTER OF ENGINEERIN

Vibration Response of a High Power Compact Large-Area Ultrasonic Resonator

Ultrasonic water treatment is based on the ability of an ultrasonic device to induce cavitation in the liquid, generating physical and chemical effects that can be exploited to produce effective treatment. This require the device be capable of generating high amplitude pressure waves in a relatively large volume of water and biological inactivation within a realistic exposure period for the application. Most conventional ultrasonic devices fulfill only the first requirement, rendering such devices highly unsuitable for use in high-volume, high-flow liquid processes. In this report, the multiple orifice radial (MOR) resonator is proposed to overcome the said limitations by offering both high vibrational amplitude and large radiating area in a relatively compact assembly. This paper discusses the approach to the MOR resonator design and follow on with experimental measurements to characterize their dynamic characteristics. Results show that the vibrational amplitudes at the radiating surfaces of the radial resonators are comparable with conventional high-output ultrasonic probes. This demonstrates the high acoustic power capability of the MOR devices proposed

Parametric Study of Multiple-Orifice Ultrasonic Resonators

No abstract available

Development of a Novel Ultrasonic Resonator for Ballast Water Disinfection

No abstract available

Development of a Novel Ultrasonic Resonator for Ballast Water Disinfection

No abstract available

An experimental study of gas nuclei-assisted hydrodynamic cavitation for aquaculture water treatment

We present an experimental study on hydrodynamic cavitation generated by accelerating liquid through a series of constrictions in the presence of gas bubbles and explore its possible applications in water treatment with particular example in aquaculture industry. The formation of intense cavitation bubbles is visualized using a high-speed photography. The cavitation is initiated when a gas bubble moves towards a narrow cylindrical constriction where it accelerates, expands and then splits into smaller bubbles owing to the sharp pressure gradient of the liquid flow inside the constriction section. As the bubbles emerge downstream from the constrictions, they are exposed to a higher pressure region and collapse violently forming a cloud of bubbles. Smaller and more dispersed bubbles are produced by further passing the bubbles through a second series of constrictions. By introducing gas bubbles that serve as cavitation nuclei prior to the constriction, it is unnecessary to force the liquid flow below its vapor pressure to produce intense cavitation, thus enhancing the cavitation activities. We also present experimental evidences of a significant reduction of gram-negative Escherichia coli concentration after exposing them to the cavitation bubbles. Yet, the cavitation bubbles are found to be not sufficiently strong to lyse endospores Bacillus subtilis that are widely used in aquacultures

Numerical and Experimental Studies of Collapsing Cavitation Bubbles for Ballast Water Treatment

In this paper, we report both experimental and computational studies of hydrodynamic cavitation generated by accelerating liquid through a series of constrictions. The detailed process of cavitation generation is visualized using a high-speed photography. The cavitation is initiated when a gas bubble moves towards the constrictions. The gas bubble initially accelerates, expands and then splits into smaller bubbles when it moves along the constriction. As these bubbles migrate into a large liquid compartment, they collapse violently to form a bubble cloud, owing to a sudden jump in liquid pressure in the compartment. The experimental observation is further confirmed using computational fluid dynamics (CFD) simulations. We also present experimental evidence showing a significant reduction in gram-negative Escherichia coli concentration after it passes through the constrictions