New procedure for determining equivalent deep-water wave height and design wave heights under irregular wave conditions

Kang, Haneul,Chun, Insik,Oh, Byungcheol The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.-

Many coastal engineering designs utilize empirical formulas containing the Equivalent Deep-water Wave Height (EDWH), which is normally given a priori. However, no studies have explicitly discussed a method for determining the EDWH and the resulting design wave heights (DEWH) under irregular wave conditions. Unfortunately, it has been the case in many design practices that the EDWH is incorrectly estimated by dividing the Shallow-water Wave Height (SWH) at the structural position with its corresponding shoaling coefficient of regular wave. The present study reexamines the relationship between the Shallow-water Wave Height (SWH) at the structural position and its corresponding EDWH. Then, a new procedure is proposed to facilitate the correct estimation of EDWH. In this procedure, the EDWH and DEWH are determined differently according to the wave propagation model used to estimate the SWH. For this, Goda's original method for nonlinear irregular wave deformation is extended to produce values for linear shoaling. Finally, exemplary calculations are performed to assess the possible errors caused by a misuse of the wave height calculation procedure. The relative errors with respect to the correct values could exceed 20%, potentially leading to a significant under-design of coastal or harbor structures in some cases.

New procedure for determining equivalent deep-water wave height and design wave heights under irregular wave conditions

Kang, Haneul,Chun, Insik,Oh, Byungcheol The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.1

Many coastal engineering designs utilize empirical formulas containing the Equivalent Deep-water Wave Height (EDWH), which is normally given a priori. However, no studies have explicitly discussed a method for determining the EDWH and the resulting design wave heights (DEWH) under irregular wave conditions. Unfortunately, it has been the case in many design practices that the EDWH is incorrectly estimated by dividing the Shallow-water Wave Height (SWH) at the structural position with its corresponding shoaling coefficient of regular wave. The present study reexamines the relationship between the Shallow-water Wave Height (SWH) at the structural position and its corresponding EDWH. Then, a new procedure is proposed to facilitate the correct estimation of EDWH. In this procedure, the EDWH and DEWH are determined differently according to the wave propagation model used to estimate the SWH. For this, Goda's original method for nonlinear irregular wave deformation is extended to produce values for linear shoaling. Finally, exemplary calculations are performed to assess the possible errors caused by a misuse of the wave height calculation procedure. The relative errors with respect to the correct values could exceed 20%, potentially leading to a significant under-design of coastal or harbor structures in some cases.

해안구조물 전면의 Stem Wave 특성에 관한 연구

박효봉(HYO-BONG PARK),윤한삼(HAN-SAM YOON),류청로(CHEONG-RO RYU) 한국해양공학회 2003 韓國海洋工學會誌 Vol.17 No.5

Numerical experiments have been conducted using the nonlinear combined refraction-diffraction model, in order to analyze the generation characteristics of stem wave, which is formed by the interaction between vertical structure and the oblique incident waves. The results of stem wave are discussed through the stem wave height distribution along/normal vertical structure, under the wide range of incident wave conditions-wave heights, periods, depths, and angles. Under the same wave height and period, the larger the incident wave angle, the higher the stem wave heights. According to the results of wave height distribution, in front of vertical structure, the maximum of stem wave heights occurs in the location bordering the vertical wall. Furthermore, the most significant result is that stem waves occur under the incident angles between 0° and 30°, and the stem wave height ratio has the maximum value, which is approximately 1.85 times the incident wave height when the incident wave angle becomes 23°.

Characteristics of an interfacial wave in a horizontal air-water stratified flow

Bae, Byeonggeon,Ahn, Taehwan,Jeong, Jaejun,Kim, Kyungdoo,Yun, Byongjo Elsevier 2017 International journal of multiphase flow Vol.97 No.-

<P><B>Abstract</B></P> <P>Interfacial wave parameters, in this case the frequency, height, velocity, and slope, were investigated experimentally in a horizontal air-water stratified flow. Experiments were conducted with a parallel wire conductance sensor and PIV visualization in a rectangular channel, of which the width and height are 40 mm and 50 mm, respectively. In the experiments, the flow condition covered the liquid Reynolds number Re<SUB>l</SUB> range of 450 to 3540 and the gas Reynolds number Re<SUB>g</SUB> range of 14,000 to 70,000. The results revealed that the observed wave types according to the flow conditions in the rectangular channel are similar to those in a horizontal pipe. The frequency, height, and slope of the interfacial wave show complicated tendencies according to the combination of Re<SUB>g</SUB> and Re<SUB>l</SUB>, which affects the coalescence and breakup of the wave. Specifically, the wave height and wave slope have opposite tendencies regarding the criterion of Re<SUB>g</SUB> = 34,000. For cases in which Re<SUB>g</SUB> ≥ 34,000, the interfacial drag force significantly affects the height and slope of the disturbance wave. In contrast, for Re<SUB>g</SUB> < 34,000, the growth of the wave has an important effect on the wave parameters. Finally, new empirical correlations for the frequency, height, and slope of the interfacial wave were proposed for application to the development of a droplet entrainment model in a horizontal stratified flow.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The frequency, height, velocity, and slope of interfacial wave are investigated experimentally in horizontal stratified flow. </LI> <LI> Characteristics of wave parameters are closely related to the wave types appeared depending on the combination of Re<SUB>g</SUB> and Re<SUB>l</SUB>. </LI> <LI> Correlations for the frequency, height, and slope of the interfacial wave are proposed. </LI> </UL> </P>

쇄파고의 확률밀도 함수를 이용한 최대파고의 확률분포 추정

김동현(Dong Hyawn Kim) 한국연안방재학회 2015 한국연안방재학회지 Vol.2 No.2

A new method treating maximum wave height as random variable was proposed. The ratio of maximum wave height to significant wave height is defined as a new random variable in this study. Then, maximum wave height is expressed as a multiplication of the ratio by significant wave height. It was shown that probability density function (PDF) of the wave height ratio derived from non-breaking wave environment can be also used in describing statistical behavior of breaking waves if appropriate shape parameter for the PDF is used. It was also shown that a shape parameter can be numerically obtained by analyzing a series of waves generated by two phases Rayleigh distribution. In addition, PDFs of maximum wave height according to significant wave heights were derived, presented and compared. Some examples were used to show how those findings are reliable.

Estimation of Design Wave Height for the Waters around the Korean Peninsula

Lee, Dong-Young,Jun, Ki-Cheon The Korean Society of Oceanography 2006 Ocean science journal Vol.41 No.4

Long term wave climate of both extreme wave and operational wave height is essential for planning and designing coastal structures. Since the field wave data for the waters around Korean peninsula is not enough to provide reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. Basic data base of hindcasted wave parameters such as significant wave height, peak period and direction has been established continuously for the period of 25 years starting from 1979 and for major 106 typhoons for the past 53 years since 1951 for each grid point of the North East Asia Regional Seas with grid size of 18 km. Wind field reanalyzed by European Center for Midrange Weather Forecasts (ECMWF) was used for the simulation of waves for the extra-tropical storms, while wind field calculated by typhoon wind model with typhoon parameters carefully analyzed using most of the available data was used for the simulation of typhoon waves. Design wave heights for the return period of 10, 20, 30, 50 and 100 years for 16 directions at each grid point have been estimated by means of extreme wave analysis using the wave simulation data. As in conventional methodsi of design criteria estimation, it is assumed that the climate is stationary and the statistics and extreme analysis using the long-term hindcasting data are used in the statistical prediction for the future. The method of extreme statistical analysis in handling the extreme vents like typhoon Maemi in 2003 was evaluated for more stable results of design wave height estimation for the return periods of 30-50 years for the cost effective construction of coastal structures.

해양파의 개별파고 분포에 대하여

김도영 한국해양공학회 2007 韓國海洋工學會誌 Vol.21 No.2

If the sea is narrowband, the Rayleigh distribution introduced by Longuet-Higgins can be used for the individual wave height distribution. However, the Rayleigh distribution often over-predicts the probability of high waves. Longuet-Higgins introduced an alternative form of the Rayleigh distribution with an empirical constant. The wave height distribution can be fitted well by one parameter Rayleigh distribution with a proper choice of the empirical constant. In this paper, the empirical constant is determined by a ratio of the significant wave height, bused on the time domain analysis and the spectral analysis. Here we examine wave data that contain extreme waves. The empirical constant in the modified Rayleigh distribution is determined simply by a ratio of significant wave heights, based on the time-domain method and wave spectrum. We confirmed that extreme wave height distribution can be modeled well by a modified Rayleigh distribution.1. 서 론

서보 모터 기반의 해양파고 및 파향 검교정 시스템 연구

박상현,박종수,배동진,김진술,박용팔 한국지식정보기술학회 2018 한국지식정보기술학회 논문지 Vol.13 No.6

In this paper, we propose a servo-motor-based system for verifying and calibrating a device for measuring the height and direction of ocean wave. Internationally, there are many devices that measure the height and direction of ocean wave, but there is no standard data and verification device. Generally, companies develop wave measurement equipment in their manufacture, but we do not know how they produce their products. In this paper, we try to calibrate the measurement devices using two servo-motors for the wave and divergence of various devices. Each servomotor controls the wave height and the wave direction. The wave can be calibrated up to 2m and the wave direction can be calibrated in 360° direction. Besides, we develop a separate monitoring device for the calibration process which can compare and analyze the waveform in real time. Consequently, we carry out a comparative analysis experiment between the waveguide measuring device and the calibrating device. Subsequently, the accuracy of the device is confirmed by comparing and analyzing the result graph value of the comparative analyzing device. Direction is the element to confirm the direction of wave. It does not measure speed and height, but it compares and analyzes the direction values between 0°~360° direction. In addition, the verification process is conducted using the results of comparative analysis. Our calibration device can produce long-waves and short-waves of ocean wave height. Our calibrator has been designed to calibrate up to 40Kg of equipment. In South Korea, each company has its ocean wave height and calibrating device, but they can not reproduce long-wave and shortwave. Furthermore, our calibrating device can be applied to ocean wave research and various fields.

대진폭 해양파의 특성에 대한 연구

김도영(Do Young Kim) 한국해양환경공학회 2009 한국해양환경·에너지학회지 Vol.12 No.1

이 논문에서는 freak wave가 포함된 시계열 파랑자료를 분석하였다. freak wave가 포함된 자료와 포함되지 않은 자료에 대하여 여러 가지 파랑 특성을 비교하였다. 파랑 자료는 Yura 해역에서 24시간 연속으로 측정된 자료를 분석하였고, 그 중에서 freak wave가 발생한 30분 동안 파랑과 인접한 30분간의 파랑자료를 집중적으로 분석하였다. 최대파의 파주기가 가장 긴 주기가 아닌 것을 볼 수 있다. 최대파의 파주기는 평균파주기보다 약간 길며, 유의파의 파주기보다는 짧은 것을 볼 수 있었다. 비록 해상 상태는 높지만, 레일리분포로 파고의 확률분포를 잘 표시할 수 있었다. Freak wave의 발생 전후의 파랑자료를 비교해 보면, 파랑스펙트럼의 특성은 큰 차이를 보이지 않으며, 발생한 경우에 비선형성이 증가한 것을 볼 수 있다. 그리고 freak wave 발생 직 후에 오히려 유의파고의 크기가 크게 나타났다. 따라서 유의 파고가 높은 것이 항상 freak wave의 발생확률을 높이지는 않는 것을 볼 수 있다. In this paper time series wave data which contain a freak wave is investigated. Various wave characteristics are compared between wave data with a freak wave and without. Among 24 hour wave data measured in the Yura Sea, two adjacent 30 min wave data with and without a freak wave are examined intensively. It is seen that the highest waves do not have the longest wave period. The wave period of the longest period waves is a little longer than the average wave period and much shorter than the significant wave period. Although the sea state is quite high, the Rayleigh distribution fits well to the probability of wave height. The characteristics of the wave spectra do not change much, but the nonlinearity increases for the wave data with a freak wave. The significant wave height without a freak wave is larger than that with a freak wave. Hence, the higher significant wave height does not always increase the probability of the occurrence of the freak waves.

Leading Depression N (LDN) Wave 조파기법에 기초한 Hybrid Breaker의 지진해일 처오름 저감효과 수치해석

조용준(Yong Jun Cho),나동규(Dong Gyu Na) 한국해안해양공학회 2015 한국해안해양공학회 논문집 Vol.27 No.1

지진해일에 대한 기존의 연구는 이차원 Boussinesq 모형과 Solitary wave에 기초한 수치해석이 그 주류를 이룬다. 최근 Solitary wave에 의한 처오름 높이가 관측치를 하회한다는 인식에 기초하여 지진해일 내습전 해안선이 전진하는 현상의 모의가 가능한 Leading Depression N (LDN) Wave가 제시되었으며 이에 기초하는 경우 보다 정확한 모의가 가능한 것으로 보고된 바 있다. 이러한 성과에도 불구하고 수리모형 실험의 경우 안정적인 Leading Depression N (LDN) Wave의 구현에 상당한 어려움을 겪어왔다. 이러한 이차원 Boussinesq 모형과 삼차원 수리모형 실험에서의 상충된 결과는 이차원 Boussinesq 계열 파랑 모형 유도과정에서 수행되는 파랑의 비선형성과 분산성이 균형을 이룬다는 가정과 이로 인해 다소 과소하게 평가된 분산성에 기인하는 것으로 판단된다. 이러한 인식에 기초하여 본고에서는 삼차원 수치수조에서 비교적 안정적인 LDN 파형의 조파가 가능한 수정 조파기법과 Navier Stoke 파랑모형에 기초하여 Hybrid Breaker의 지진해일에 의한 처오름 저감효과를 수치 해석하였다. 파랑모형의 검증은 불규칙 파랑을 대상으로 기 수행된 수리모형 실험결과를 토대로 진행되었으며, 그 결과 비교적 근접한 처오름 높이를 얻을 수 있었다. 세 개의 유수실과 전면 경사면으로 구성된 Hybrid Breaker의 경우 일반 경사제에 비해 H = 5m의 경우 약 13%, H = 6 m의 경우 10%정도의 처오름 저감 효과를 지니는 것으로 모의되었다. Past study of tsunami heavily relied on the numerical modelling using 2D Boussinesq Eq. and Solitary wave. Lately, based on the fact that numerically simulated run up heights based on solitary wave are somewhat smaller than the measured one, Leading Depression N (LDN) Wave has been elaborated, which can account the advancement of a shore line before tsunami strikes a shore. Thereafter it is reported that more accurate simulation can be possible once LDN is deployed. On the other hand, there were numerous reports indicating that stable LDN wave can’t be sustained in the hydraulic model test. These conflicts between the hydraulic model tests and numerical results have their roots on the assumption made in the derivation of Boussinesq type wave model such as that wave nonlinearity is equally balanced with wave dispersiveness. Hence, in the numerical simulation based on the Boussinesq type wave model, wave dispersiveness is inevitably underestimated, especially in deep water. Based on this rationale, we developed the modified methodology for the generation of stable LDN wave in the 3D numerical wave flume, and proceeded to numerically analyze the depression effect of Hybrid Breaker on the run up height due to tsunami using the Navier Stoke Equation. The verification of newly proposed wave model in this study was carried out using the run up height from the hydraulic model test. It was shown that Hybrid Breaker consisting of three water chamber and slope at its front can reduce 13% of run up height for H = 5m, and 10% of run up height for H = 6m.