An objective comparison of commercially-available cavitation meters

Abstract

With a number of cavitation meters on the market which claim to characterise fields in ultrasonic cleaning baths, this paper provides an objective comparison of a selection of these devices and establishes the extent to which their claims are met. The National Physical Laboratory's multi-frequency ultrasonic reference vessel provided the stable 21.06kHz field, above and below the inertial cavitation threshold, as a test bed for the sensor comparison. Measurements from these devices were evaluated in relation to the known acoustic pressure distribution in the cavitating vessel as a means of identifying the mode of operation of the sensors and to examine the particular indicator of cavitation activity which they deliver. Through the comparison with megahertz filtered acoustic signals generated by inertial cavitation, it was determined that the majority of the cavitation meters used in this study responded to acoustic pressure generated by the direct applied acoustic field and therefore tended to overestimate the occurrence of cavitation within the vessel, giving non-zero responses under conditions when there was known to be no inertial cavitation occurring with the reference vessel. This has implications for interpreting the data they provide in user applications.

A Theoretical Model for the Asymmetric Transmission of Powerful Acoustic Wave in Double-Layer Liquids

“…Just as the experimental results in Ref. [14], few bubbles are induced for the L-R transmission, which means that the screening of bubbles [32] does not exist, and the output sound energy density (OSED) is relatively high (𝜀(2𝜆) = 0.063 J/m 3 ). However, for the R-L transmission, the cavitation bubbles converge in the region around the input end.…”

“…However, for the R-L transmission, the cavitation bubbles converge in the region around the input end. These bubbles lead to the localization of sound energy, [32,33] which results in relatively low OSED (𝜀(−2𝜆) = 0.061 J/m 3 ). The spectra at 𝜆 5 to the corresponding input ends (see Fig.…”

Asymmetrical Propagation of Powerful Sound in Double-Layer Liquid

“…On the contrary, for the R-L transmission the right liquid will be cavitated because of Pdr≥QR. As is well known, the cavitation will yield an additional attenuation called cavitation screening, [5] leading to that the R-L transmission is more difficult than the L-R transmission. In other words, the sound wave is rectified in this system.…”

Nanogenerator for determination of acoustic power in ultrasonic reactors

“…The resultant increase in membrane temperature generates a voltage across the electrodes where the magnitude is proportional to the rate of temperature change with respect to time [7] . Hydrophones are most common devices used for liquid ultrasound characterization [9] . Hydrophone design can be divided into three groups: fiber-optic devices [10] , [11] , [12] , piezoelectric ceramics [13] , [14] , [15] , and membrane transducers [16] , [17] .…”