Dependence of cavitation, chemical effect, and mechanical effect thresholds on ultrasonic frequency

• Published in: Ultrasonics sonochemistry Vol. 39; pp. 301 - 306
• Main Authors: Thanh Nguyen, Tam, Asakura, Yoshiyuki, Koda, Shinobu, Yasuda, Keiji
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2017
• Subjects: Aluminum foil erosion; Broadband noise; Cavitation threshold; Harmonic; Potassium iodide; Ultraharmonic; Harmonic; Ultraharmonic; Broadband noise; Potassium iodide; Cavitation threshold; Aluminum foil erosion
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2017.04.037

•Cavitation threshold was measured in wide frequency ranges from 22 to 4880kHz.•Thresholds of chemical effect and mechanical effect were investigated first time.•Chemical effect threshold was close to cavitation threshold.•Mechanical effect threshold was higher than cavitation threshold above 98kHz.•Thresholds of the second harmonic and the first ultraharmonic were also measured. Cavitation, chemical effect, and mechanical effect thresholds were investigated in wide frequency ranges from 22 to 4880kHz. Each threshold was measured in terms of sound pressure at fundamental frequency. Broadband noise emitted from acoustic cavitation bubbles was detected by a hydrophone to determine the cavitation threshold. Potassium iodide oxidation caused by acoustic cavitation was used to quantify the chemical effect threshold. The ultrasonic erosion of aluminum foil was conducted to estimate the mechanical effect threshold. The cavitation, chemical effect, and mechanical effect thresholds increased with increasing frequency. The chemical effect threshold was close to the cavitation threshold for all frequencies. At low frequency below 98kHz, the mechanical effect threshold was nearly equal to the cavitation threshold. However, the mechanical effect threshold was greatly higher than the cavitation threshold at high frequency. In addition, the thresholds of the second harmonic and the first ultraharmonic signals were measured to detect bubble occurrence. The threshold of the second harmonic approximated to the cavitation threshold below 1000kHz. On the other hand, the threshold of the first ultraharmonic was higher than the cavitation threshold below 98kHz and near to the cavitation threshold at high frequency.