Flume Experiments on Energy Conversion Behavior for Oscillating Buoy Devices Interacting with Different Wave Types

Oscillating buoy device, also known as point absorber, is an important wave energy converter (WEC) for wave energy development and utilization. The previous work primarily focused on the optimization of mechanical design, buoy’s array configuration and the site selection with larger wave energy density in order to improve the wave energy generation performance. In this work, enlightened by the potential availability of Bragg reflection induced by multiple submerged breakwaters in nearshore areas, we investigate the energy conversion behavior of oscillating buoy devices under different wave types (traveling waves, partial and fully standing waves) by flume experiments. The localized partial standing wave field is generated by the Bragg resonance at the incident side of rippled bottoms. Furthermore, the fully standing wave field is generated by the wave reflection of vertical baffle installed in flume. Then the wave power generation performance is discussed under the conditions with the same wave height but different wave types. The experimental measurements show that the energy conversion performance of the oscillating buoy WEC could be improved under the condition of standing waves when compared with traveling waves. This work provides the experimental comparison evidence of wave energy conversion response of oscillating buoy devices between travelling waves and standing (fully or partial) wave conditions.

Gravity-Aided Ultrasonic Separation of Nanoparticles from Liquid Using Macro-Scale Separator

Acoustophoresis is the technology to separate the microparticles and cells from suspending fluid. This research focuses on the separation of nanoparticles from water by using macro-scale fluidic separator which works based on gravity-aided ultrasonic standing wave technology. Titanium dioxide particles of 40 nm diameter were concentrated by the combination of ultrasonic standing wave field at 2.2 MHz and gravity-aided sedimentation. The purpose of this study is to investigate the performance of gravity-aided ultrasonic particle to concentrate nanoparticles. It was found that the separation efficiency is 83% at a flow rate of 0.1 mL/min. FEM simulations were also conducted to evaluate characteristics of variation of acoustic energy inside the fluidic channel. Results indicate that nanoparticles can be concentrated using gravity-aided ultrasonic standing wave field, however optimization of the design of the fluidic channel is required for increasing throughput of the separator.

Optimization of Ultrasonic Acoustic Standing Wave Systems

Ultrasonic acoustic standing wave systems find use in many industrial applications, such as sonochemical reactions, atomization of liquids, ultrasonic cleaning, and spray dry. In most applications, highest possible sound pressure levels are needed to achieve optimum results. Until now, the atomization of liquids is limited to fluids with low viscosity, as systems generating sufficient sound pressure for atomizing fluids with higher viscosities are often not marketable due to their low throughput or high costs. For the production of polymer or metal powders or the dispensing of adhesives, highest sound pressures should be achieved with systems in suitable size, with good efficiency and at low cost but without contamination of sonotrodes and reflectors by the dispersed media. An alternative to the use of more powerful transducers is increasing the intensity of the acoustic standing wave field by optimizing the boundary conditions of the acoustic field. In most existing standing wave systems a part of the radiating sound waves does not contribute to the process, as the waves spread into the wrong direction or wipe themselves out due to interference. In order to obtain maximum sound pressure amplitudes in the standing wave field, all waves should be trapped between the sonotrode and the reflector. In addition, the resonance condition should be met for all radiated waves. These conditions can be fulfilled by optimizing the shapes of sonotrode and resonator as well as the distance between them. This contribution reports on a model, which is able to simulate the sound field between a transducer surface and a reflector. Using a linear finite-element model, the boundary conditions of the standing wave system are optimized. Sound pressure levels of the standing wave field are calculated for different shapes of reflectors and boundary conditions like the distance between the transducer and the reflector. The simulation results are validated by sound-field measurements via refracto-vibrometry and a microphone. Finally, optimization guidelines for the generation of high-intensity acoustic standing wave fields are shown and verified by measurements.

Analysis of the effects of acoustic levitation to simulate the microgravity environment on the development of early zebrafish embryos

Influence of acoustic standing wave field creating acoustic levitation, on each development stage of early zebrafish embryos has been studied.