A study on the estimation of bubble size distribution using an acoustic inversion method

Cheolsoo Park; So Won Jeong; Gun Do Kim; Ilsung Moon; Geuntae Yim

doi:10.7776/ASK.2020.39.3.151

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2020 Vol.39, Issue 3 Preview Page Next Page

Research Article

A study on the estimation of bubble size distribution using an acoustic inversion method 음향 역산법을 이용한 기포의 크기 분포 추정 연구

31 May 2020. pp. 151-162

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Abstract

This paper presents an acoustic inversion method for estimating the bubble size distribution. The estimation error of the attenuation coefficient represented by a Fredholm integral equation of the first kind is defined as an objective function, and an optimal solution is found by applying the Levenberg-Marquardt (LM) method. In order to validate the effectiveness of the inversion method, numerical simulations using two types of bubble distribution are performed. In addition, a series of experiments are carried out in a water tank (1.0 m × 0.54 m × 0.6 m), using bubbles generated by three different generators. Images of the distributed bubbles are obtained by a high-speed camera, and the insertion losses of the bubble layer are measured using a source and a hydrophone. The image is post-processed to glance a distribution characteristics of each bubble generator. Finally, the size distribution of bubbles is estimated by applying the inversion method to the measured insertion loss. From the inversion results, it was observed that the number of bubbles increases exponentially as the bubble size decreases, and then increases again after the local peak at 70 μm - 120 μm.

Keywords

Bubble size distribution

Acoustic inversion

Insertion loss

Bubble experiment

본 논문에서는 음향 역산법을 이용한 기포의 크기 분포 추정 기법을 제시하였다. 제 1종 Fredholm 적분방정식으로 표현된 감쇠계수의 추정오차를 목적함수로 정의하였고, 최적해를 구하기 위해 Levenberg-Marquardt(LM)기법을 적용하였다. 두 가지의 기포 분포에 대한 수치 시뮬레이션을 통해 제안된 역산 기법의 유용성을 검증하였다. 세 종류의 기포발생기를 이용하여 사각 수조(1.0 m × 0.54 m × 0.6 m)에서 기포 실험을 수행하였다. 고속카메라 촬영을 통해 기포의 분포 이미지를 획득하였고, 음원과 수중청음기를 이용하여 기포층의 주파수별 삽입손실(insertion loss)을 계측하였다. 촬영된 이미지는 후처리를 통해 기포 발생기별 기포 분포 특성을 파악하는데 활용하였고, 계측된 삽입손실에 역산 기법을 적용하여 기포의 크기 분포를 추정하였다. 음향 역산결과로부터 기포의 크기가 작아짐에 따라 기포 개수는 지수적으로 증가하며, 70 μm ~ 120 μm의 국부 피크를 지난 후 다시 증가하는 경향성을 확인하였다.

키워드

기포 크기분포

음향 역산법

삽입손실

기포 실험

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Information

Publisher :The Acoustical Society of Korea
Publisher(Ko) :한국음향학회
Journal Title :The Journal of the Acoustical Society of Korea
Journal Title(Ko) :한국음향학회지
Volume : 39
No :3
Pages :151-162
Received Date : 2020-03-16
Accepted Date : 2020-04-08
DOI :https://doi.org/10.7776/ASK.2020.39.3.151

The Journal of the Acoustical Society of Korea ISSN:1225-4428(Print) 2287-3775(Online) 한국음향학회지

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