이산 웨이블릿을 이용한 Bubbly flow의 유동분리기법
Flow Field Separating Technique in Bubbly Flow using Discrete Wavelet
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초록
입자영상속도계(PIV)의 해석에 웨이블릿 변환을 적용하여 정성적인 유동정보뿐만 아니라 공간분해능을 갖는 정량적인 속도장 정보를 제공하고 있다. 이 기법은 기포유동(bubbly flow)과 같은 다상(multi-phase)의 유동구조를 해석하는 데도 유용하게 쓰일 수 있다. 본 연구에서는 기체와 액체의 이상유동(two-pase flow)에 PIV기법을 적용하고 이산 웨이블릿 변환을 사용하여 유장해석을 수행함으로써, 기포를 포함한 속도장 특성과 유동특성을 조사한다.
Abstract
Nowadays wavelet transforms are widely used for the analyses of PIV velocity vector fields. This is because the wavelet provides not only spatial nformation of the velocity vectors but also of time and frequency domains. In this study, a discrete wavelet transform has been applied to real PIV images of bubbly flows. The vector fields obtained by a self-made cross-correlation PIV algorithm were used for the discrete wavelet transform. The performances of the discrete wavelet transform is investigated by changing the level of power of discretization. The decomposed images by the wavelet multiresolution showed conspicuous characteristics of the bubbly flows according to the level changes. The high spatial bubble concentrated area could be evaluated by the constructed discrete wavelet transform algorithm, at which high leveled wavelets could play a dominant roles to reveal the flow characteristics.
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