Journal of the Institute of Convergence Signal Processing (융합신호처리학회논문지)

The Korea Institute of Convergence Signal Processing (한국융합신호처리학회)
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Analysis of Flow Visualization Results Using Fourier Transform

퓨리에 변환을 활용한 유동 가시화 비교 분석

  • Koo, Bon-guk (Department of Naval Architecture and Marine Engineering, Changwon National University) ;
  • Park, Jun-mo (School of Electronic and Biomedical Engineering, Tongmyong University) ;
  • Kang, Yong-Duck (Department of Naval Architecture and Ocean Engineering, Dong-Eui University)
  • 구본국 (창원대학교 조선해양공학과) ;
  • 박준모 (동명대학교 전자및의용공학부) ;
  • 강용덕 (동의대학교 조선해양공학과)
  • Received : 2019.12.09
  • Accepted : 2019.12.30
  • Published : 2019.12.31
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Abstract

In the boundary layer, vortical system has been analyzed by the statistical methods to identify the vortex interaction. However, there are the limitations in explaining vortices by the mean velocity or the standard deviation. This paper proposed a method to establish a frequency analysis by Fourier transform in order to simultaneously investigate various scale vortices. For this purpose, the flow visualization conducted to reveal a standing vortex, a hairpin vortex and a wake region around a hemisphere attached on a flat plate in a water channel. In addition, the velocity where the hairpin vortex was being generated in the wake region was measured by a hot-film anemometer. To observe changes in the vortex interaction, suction was applied through a hole in front of the hemisphere. For the evaluation of the proposed frequency analysis, the existing statistical results were compared to the frequency analysis that corresponds to the qualitative results of the flow visualization.

경계층 내 측정된 유속은 변동 성분을 활용한 표준편차 혹은 배경 유속을 포함한 평균 속도로 해석되어 왔다. 하지만, 각각의 결과로 유동 상호작용을 설명하는데 한계가 있어 본 논문에서는 시간 영역의 유속을 퓨리에 변환하여 주파수 분석으로 유동 현상을 규명하는 방법을 제안한다. 이를 위해 경계층 내 평판 위에 부착된 반구 내부로 염료를 주입시켜 후류 영역에서 생성되는 머리핀 와류를 가시화하여 발생 빈도를 계측하였다. 또한 반구 전방의 평판을 뚫어 흡입함으로써 후류 영역 내 유속 변화를 열선 유속계로 측정하였다. 제안된 주파수 분석의 평가를 위해 기존의 통계 해석법과 비교하였으며, 유동의 정성적인 결과에 부합하는 주파수 분석과정을 제시한다.

Keywords

References

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