Analysis on Wave Absorbing Performance of a Pile Breakwater

J. Ocean Eng. Technol. 2007;21(4):1-7.

Cho Il-Hyoung,Koh Hyeok-Jun

Department of Marine Industrial Engineering Cheju National University,Department of Marine Industrial Engineering Cheju National University

파일 방파제의 소파성능 해석

조일형,고혁준

제주대학교 해양산업공학,제주대학교 해양산업공학

Keywords: Eigenfunction expansion method, Energy loss coefficient, Pile breakwater, Reflection Coefficient, Separation, Transmission coefficinet, Turbulent flow

핵심용어: 고유함수 전개법, 에너지 손실계수, 파일 방파제, 반사율, 박리, 투과율, 난류

Abstract

Based on the eigenfunction expansion method, the wave-absorbing performance of a square or circular pile breakwater was investigated. Flow separation resulting from sudden contraction and expansion is generated and is the main cause of significant energy loss. Therefore, evaluation of an exact energy loss coefficient is critical to enhancing the reliability of the mathematical model. To obtain the energy loss coefficient, 2-dimensional turbulent flow is analyzed using the FLUENT commercial code, and the energy loss coefficient can be obtained from the pressure difference between upstream and downstream. It was found that energy loss coefficient of circular pile is 20% that of a square pile. To validate the fitting equation for the energy loss coefficient, comparison between the analytical results and the experimental results (Kakuno and Liu, 1993) was made for square and circular piles with good agreement. The array of square piles also provides better wave-absorbing efficiency than the circular piles, and the optimal porosity value is near P=0.1.