An acoustic bubble density measurement technique for surface ship waters

Abstract

The Dual Frequency Pump Method of acoustically determining point by point bubble cloud densities was studied to determine the practicality of using this acoustic technique to determine bubble densities in surface ship wakes. The dual frequency technique of acoustically detecting bubbles utilizes a high and low frequency sound field to insonify the target bubbles. The bubbles themselves then radiate sound at the sidebands of higher frequency. The frequency of the return sound is proportional to the bubble sizes present. The Dual Frequency Pump Method of bubble detection can differentiate and count many different sized bubbles and is, therefore, well suited for determining ship wake bubble density distributions. The theory, considerations, experimental results, and recommendations of this thesis support the application of the dual frequency acoustic techniques to the ship wake problem. Keywords: Theses; Acoustic bubble density measurement; Surface ship wakes; Bubble resonance; Dual frequency bubble detection; Ultrasonic bubble detection