Journal of Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회논문집)

Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회)
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Experimental Study on Impact Pressure at the Crown Wall of Rubble Mound Seawall and Velocity Fields using Bubble Image Velocimetry

기포영상유속계와 복합파고계를 활용한 경사식 호안 전면에서 쇄파의 형태에 따른 충격쇄파압의 분류

  • Na, Byoungjoon (Coastal Development and Ocean Energy Research Center, Korea Institute of Ocean Science and Technology) ;
  • Ko, Haeng Sik (Coastal Development and Ocean Energy Research Center, Korea Institute of Ocean Science and Technology)
  • 나병준 (한국해양과학기술원 연안개발.에너지연구센터) ;
  • 고행식 (한국해양과학기술원 연안개발.에너지연구센터)
  • Received : 2022.08.05
  • Accepted : 2022.08.25
  • Published : 2022.08.31
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Abstract

To investigate varying wave impact pressure exerting at the crest wall of rubble mound seawall, depending on breaking wave properties, regular waves with different wave periods were generated. Wave velocity fields and void fraction were measured using bubble image velocimetry and simple combined wave gauge system (Na and Son, 2021). For the waves with shorter wave period, maximum horizontal velocity was less reduced compared to incident wave speed while breaking-induced air entrainment was occurred intensely, leading to a significant reduction of wave impact pressure at the crest wall. For the waves with longer wave periods, less air wave entrained and the wave structure followed a flip-through mode (Cooker and Peregrine, 1991), resulting in an abrupt increase of the impact pressure.

본 연구에서는 테트라포드로 피복된 경사식 마운드 위의 직립벽에 작용하는 충격쇄파압을 쇄파 형태에 따라 구분하기 위해 규칙파를 생성하고 충돌 직전의 유속장과 기포분율을 측정하였다. 유속장 측정을 위해 쇄파 중 발생하는 기포의 움직임을 추적하는 기포영상유속계를 사용하고 기포분율 측정을 위해 복합파고계 기법(Na and Son, 2021)을 활용하였다. 측정된 입사파의 주기가 짧을수록 최대평균유속은 사면에서 파속에 비해 적은 감소율을 보였지만 파랑이 사면을 따라 진행하며 쇄파가 더 빨리 발생하여 기포분율이 증가하였고 결과적으로 중복파압형태의 파압이 작용하였다. 주기가 큰 실험파의 경우 충돌 전 유입되는 공기가 적어 flip-through 형태(Cooker and Peregrine, 1991)의 흐름양상을 보였고, 파압이 급격하게 증가함을 확인할 수 있었다.

Keywords

Acknowledgement

해양수산과학기술진흥원(KIMST)의 "재해안전 항만 구축 기술개발(PM62370)" 사업의 지원을 받아 수행되었으며, 이에 감사드립니다. 또한 실험을 도와준 장세철, 이주연, 권창헌 씨에게 감사합니다.

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