Characterizing the cavitation development and acoustic spectrum in various liquids

Abstract

A bespoke cavitometer that measures acoustic spectrum and is capable of operating in a range of temperatures (up to 750°C) was used to study the cavitation behaviour in three transparent liquids and in molten aluminium. To relate these acoustic measurements to cavitation development, the dynamics of the cavitation bubble structures was observed in three Newtonian, optically transparent liquids with significantly different physical properties: water, ethanol, and glycerine. Each liquid was treated at 20kHz with a piezoelectric ultrasonic transducer coupled to a titanium sonotrode with a tip diameter of 40mm. Two different transducer power levels were deployed: 50% and 100%, with the maximum power corresponding to a peak-to-peak amplitude of 17μm. The cavitation structures and the flow patterns were filmed with a digital camera. To investigate the effect of distance from the ultrasound source on the cavitation intensity, acoustic emissions were measured with the cavitometer at two points: below the sonotrode and near the edge of the experimental vessel. The behaviour of the three tested liquids was very different, implying that their physical parameters played a decisive role in the establishment of the cavitation regime. Non dimensional analysis revealed that water shares the closest cavitation behaviour with liquid aluminium and can therefore be used as its physical analogue in cavitation studies; this similarity was also confirmed when comparing the measured acoustic spectra of water and liquid aluminium.

Investigation of Acoustic Streaming and Cavitation Intensity in Water as an Analogue for Liquid Metal

“…that within the same flow there are distinctive secondary multi-directional flows with dynamic recirculating flow patterns, together with strong eddies near the transducer and free surface under the same experimental conditions [20], may provide for a more efficient treatment of the liquid, even though velocity magnitudes are lower than at 100% power. This arises because flow paths are more varied and excessive recirculation (vortex) regions are avoided, helping to ensure macro-scale homogenisation of the liquid, noting that even at 50% power cavitation remains vigorous, as described in [23].…”

Validation of the Physical Simulations of a Stirred Molten Metal Using Particle Image Velocimetry Data

“…On each occasion the HSM was placed in a slightly off-center position of the tank to avoid unnecessary surface vortexing in an unbaffled vessel. 23 Still photos and movies were taken by a Fuji digital camera and a PIV system. 24 The water was seeded with 8-12-lm hollow glass spheres.…”

Ultrasonic mixing head for liquid composite molding: Process and material characteristics

“…The temperature delta in the UMH clearly depends on the amplitude. At high amplitudes, the ultrasonically treated area that enables bubble creation is larger [34]. More implosions of collapsing bubbles imply more heat dissipation in the resin system-the temperature rises.…”