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.

3차원 수치파동수조에서 수중발파에 의한 수면파의 전파해석

이우동,정연명,최규남,허동수 한국해양공학회 2019 韓國海洋工學會誌 Vol.33 No.4

When underwater blasting is conducted, both shock waves and water waves have an effect on adjacent coastal areas. In this study, an empirical formula for estimating the details of water waves caused by underwater blasting was applied to a non-reflected wave generation system, and a 3D numerical wave tank (NWT) was improved to reproduce the generation and propagation of such water waves. The maximum elevations of the propagated water waves were comparatively analyzed to determine the validity and effectiveness of the NWT. Good agreement was demonstrated between the empirical and simulation results. The generation and propagation of water waves were also simulated under each underwater blasting scenario for the removal of the Todo islet at the Busan Newport International Terminal (PNIT). It was determined that the water waves generated by the underwater blasting scenario examined in this study did not have a significant impact on the PNIT. In addition, multiple-charge blasting caused higher wave heights than single-charge blasting. As the amount of firing charge increased, the wave height also increased. Finally, larger water waves were generated during the later blasting conducted at a deeper depth as compared with an earlier blasting conducted at a relatively shallow depth.

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.

섬유주의 이방성에 따른 초음파의 파형 변화

윤원석(Yoon, Won-Sok),윤영준(Yoon, Young-June) 한국정보전자통신기술학회 2011 한국정보전자통신기술학회논문지 Vol.4 No.4

높은 기공성을 갖춘 망상골과 고체의 비율이 높은 피질골의 기계적 성질은 초음파 파동 전파 측정법으로 알 수 있다. 초음파의 속도(SOS)는 bulk wave 방정식과 bar wave 방정식을 통해 산출할 수 있다. Bulk wave는 Biot의 이론에서 빠른 파동과 매우 유사함을 이용해, 본 연구에서 뼈의 이방성을 담은 행렬에 의해 bulk wave 속도가 변하는 여부를 측정하였다. 음파의 속도는 뼈가 횡방적인(transversely isotropy) 특성을 갖을 때보다 등방적인 특성을 갖을 때 0.69% 빠르다. 또한 bar wave 방정식을 사용하여 피질골에 대한 속도를 측정하였다. 전의 논문에 의하면 bar wave 속도는 탄성 계수 텐서 혹은 영의 계수의 함수이고 이와 같은 방법으로 bar wave 속도에 의해 등방성과 이방성을 측정하였다. Mechanical properties of cancellous bone with a high porosity and cortical bone with a high fraction of solid are estimated by the measurement of ultrasonic wave propagation. The speed of sound (SOS) in ultrasonic waves is usually measured by two equations, bulk wave equation and bar wave equation. Bulk wave speed has almost same as the fast wave of Biot's theory. In this study, we examine whether the bulk wave speed is influenced by the anisotropy of bone matrix. The SOS when the bone matrix is isotropy is 0.69% faster than that when the bone matrix is transversely isotropy. We also examine if the use of bar equation is adequate for a cortical bone. In the previous paper, the bar wave speed is a function of Young's modulus or elastic coefficient tensor. In the same manner, the effect of bar wave speed to isotropic and anisotropic bone is estimated.

유한요소해석 및 방사음장해석에 의한 판형 웨이브가이드 센서의 방사 빔 조향 해석 및 실험적 검증

박상진,주영상,김회웅,박창규 한국비파괴검사학회 2022 한국비파괴검사학회지 Vol.42 No.6

A plate-type waveguide (WG) sensor is a remote ultrasonic inspection device developed for severe environments such as high temperature and high radioactivity. A WG sensor uses the ability of long-distance propagation of Ao-mode Lamb wave and phenomenon of leaky Lamb wave. In addition, it can steer the radiation beam based on the phase velocity dispersion characteristics of the Ao-mode Lamb wave. Particularly, the beam steering technique is an electrical steering method that can change the radiation angle depending on the excitation frequency without the physical movement of the sensor. In this study, we analyze the steering characteristics of the radiation beam radiated from the WG sensor using finite element analysis and Rayleigh-Sommerfeld integral (RSI) analysis. Two dimensional simulations for the Ao-mode Lamb wave propagation and radiation with three types of excitation frequencies are performed, and simulation results of the radiation beam profile are experimentally demonstrated using the measured underwater results. The radiation angle of the radiation beam profiles obtained from the constructed two analysis models corresponds well with that of the measurement results, and the radiation characteristics such as near-field distance are validated to change with a change in the radiation angle depending on the excitation frequency. 판형 웨이브가이드 센서는 고온, 고방사능과 같은 가혹한 환경에서 초음파 트랜스듀서에 어떠한 물리적 손상이나 성능 저하없이 검사할 수 있는 원격 초음파 검사 센서이다. 개발한 웨이브가이드 센서는 웨이가이드 판을 따라 전파하는 Ao-모드 판파의 장거리 전파 성능과 누설 판파 현상을 이용하며, Ao-모드 판파의 위상속도 분산특성을 기반으로 초음파 방사 빔을 조향할 수 있다. 특히 방사 빔 조향 기능은 센서의 기계적 구동없이 전기적으로 가진주파수를 조정하는 것만으로 방사 빔의 방출 각도를 바꿀 수 있다. 본 논문에서는 유한요소해석 및 RSI(Rayleigh-Sommerfeld Integral) 방사 빔 해석 모델을 구축하여 웨이브가이드 센서의 방사 빔 조향 특성을 분석하였다. 세 가지 가진 주파수 변화와 함께 Ao-모드 판파의 전파 및 방사현상에 대한 2차원 시뮬레이션을 수행하였고, 방사 빔 프로파일 시뮬레이션 결과를 수중에서 측정된 방사 빔 프로파일과 비교하여 해석결과를 검증하였다. 구축한 두 모델로부터 얻은 방사 빔 프로파일의 방사각은 실험에서 측정한 결과와 잘 일치하였으며 가진 주파수 변화에 따라 방사 각도도 변화하지만 근거리음장 거리와 같은 방사 특성도 같이 변화한다는 사실을 확인하였다.

Numerical simulation of pulse wave propagation in a curved artery

Fan He,Lu Hua,Li-jian Gao 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1

Objective: To set up a model of pulse wave propagation in a curved artery and compare the differences of pulse wave propagation between straight and curved arteries. Methodology: In previous work, we deal with a three-segment wave propagation model in a straight tube. In this paper, as a follow up study, we construct a wave propagation model in a curved artery based on the three-segment model developed in a straight tube. Numerical simulation is performed using a fluid-structure interaction. Findings: The comparison of this curved model and previous straight model indicates that arterial geometry has a significant impact on pulse wave propagation. An obvious time delay occurs whether between the peaks or between the bottoms in a straight tube. However, the time delay only occurs between the bottoms in a curved artery while it does not clearly exist between the peaks. The finding indicates that a time delay between bottoms is more stable and easy to catch. Actually, a velocity wave is just quantized by usually measuring a time delay between bottoms in clinics and experiments. Modeling of pulse wave propagation in a curved artery and the use of wave propagation model can be better made to perform hemodynamic distributions and predict vascular disorders.

층상 waveguide에서의 SH파 전파 해석을 위한 경계조건

이진호 한국전산구조공학회 2021 한국전산구조공학회논문집 Vol.34 No.2

무한 매질에서의 파전파 현상은 공학과 자연과학의 여러 분야에서 다양한 물리적 현상을 서술하는데 활용되고 있고, 이 문제에 대한 해를 얻기 위하여 해석적 방법 또는 수치적 방법이 개발되어 사용되고 있다. 이 문제에 대한 정확한 해를 얻기 위해서는 무한 영역으로의 에너지 방사를 정확히 고려해야 하고, 이를 위해 다양한 수치적 또는 역학적 모형 또는 경계조건이 개발되었다. 이 연구에서는 층상 waveguide에서의 scalar wave 또는 SH파 전파 문제에 적용할 수 있는 새로운 경계조건을 제안하고자 한다. 이를 위해 waveguide 의 수직방향으로 유한요소 이산화를 적용하여 얻은 SH파의 지배방정식을 변형하여 waveguide의 무한 영역의 영향을 나타내는 경계조건을 유도한다. 층상 waveguide에서의 SH파에 대한 고유모드의 직교성을 이용하여, 새로운 경계조건은 기존의 root-finding absorbing boundary condition와 동등함을 보이고, 이로부터 새로운 경계조건의 차수가 증가할수록 정확성이 증가하고, 또한 이산화된 수준에서도 안정함을 유도할 수 있다. 제안된 경계조건을 층상 waveguide에서의 파전파 문제에 적용하여 그 정확성과 안정성을 검증한다. The wave-propagation phenomenon in an infinite medium has been used to describe the physics in many fields of engineering and natural science. Analytical or numerical methods have been developed to obtain solutions to problems related to the wave-propagation phenomenon. Energy radiation into infinite regions must be accurately considered for accurate solutions to these problems; hence, various numerical and mechanical models as well as boundary conditions have been developed. This paper proposes a new boundary condition that can be applied to scalar-wave or horizontally-polarized shear-wave (or SH-wave) propagation problems in layered waveguides. A governing equation is obtained for the SH waves by applying finite-element discretization in the vertical direction of the waveguide and subsequently modified to derive the boundary condition for the infinite region of the waveguide. Using the orthogonality of the eigenmodes for the SH waves in a layered waveguide, the new boundary condition is shown to be equivalent to the existing root-finding absorbing boundary condition; further, the accuracy is shown to increase with the degree of the new boundary condition, and its stability can be proven. The accuracy and stability are then demonstrated by applying the proposed boundary condition to wave-propagation problems in layered waveguides.

Theoretical and numerical analysis of the influence of initial stress gradient on wave propagations

Tao, Ming,Chen, Zhenghong,Li, Xibing,Zhao, Huatao,Yin, TuBing Techno-Press 2016 Geomechanics & engineering Vol.10 No.3

The investigation of stress wave propagation in a medium with initial stress has very important application in the field of engineering. However, the previous research less consider the influence of initial stress gradient on wave propagation. In the present paper, the governing equation of wave propagation in elastic continuum material with inhomogeneous initial stress is derived, which indicated that the inhomogeneous initial stress changed the governing equation of wave propagation. Additionally, the definite problem of wave propagation in material with initial stress gradient is verified by using mathematical physics method. Based on the definite problem, the elastic displacement-time relationship of wave propagation is explored, which indicated that the inhomogeneous initial stress changed waveform and relationship of displacement-time histories. Furthermore, the spall process of blasting wave propagation from underground to earth surface is simulated by using LS-DYNA.

정상초음파의 주파수 변화에 따른 C3H8-Air 예혼합화염의 전파거동 및 구조변이

이상신,서항석,김정수 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.2

The propagation behavior and structural variation of a premixed propane/air flame with frequency change in an ultrasonic standing wave at various equivalence ratios were experimentally investigated using Schlieren photography and pressure measurement. The propagating flame was observed in high-speed Schlieren images, allowing local flame velocities of the moving front to be analyzed in detail. The study reveals that the distorted flame front and horizontal splitting in the burnt zone are due to the ultrasonic standing wave. Vertical locations of the distortion and horizontal stripes are intimately dependent on the frequency of the ultrasonic standing wave. In addition, the propagation velocity of the flame front bounded by the standing wave is greater than that of the flame front without acoustic excitation. As expected, the influence of the ultrasonic standing wave on premixed-flame propagation becomes more prominent as the frequency increases. 정상초음파장의 주파수 변이가 프로판/공기 예혼합화염의 전파거동 및 구조변이에 미치는 영향을 규명하기 위해 실험적 연구를 수행하였다. 다양한 당량비 조건에서 슐리렌 기법을 적용한 전파화염 가시화와 연소실 내부압력 측정을 통해 생성물 영역에서의 화염 구조변화 및 전파특성을 관찰하였다. 정상초음파가 존재할 경우 화염선단이 찌그러지고 기연부에서 횡방향 줄무늬가 생성되며, 이러한 구조변이는 정상초음파의 주파수에 종속한다. 또, 전파속도는 정상초음파가 교반하는 경우 증가되며, 화염전파 거동에 미치는 초음파의 영향은 주파수의 증가에 따라 보다 명확해진다는 사실도 확인되었다.

폴리머 박판에서 판파의 속도 측정에 의한 소재 특성 고찰

김용연 ( Yong Yun Kim ) 충북대학교 건설기술연구소 2011 建設技術論文集 Vol.30 No.2

탄성파동을 적용하여 횡적 등방성 매체인 페놀수지의 소재 특성을 평가하였다. 균일 직교 매체에서 파동을 이론적으로 고찰하기 위해 먼저 무한계에서 체적파의 파동을 해석하고, 평판에서 전파되는 파의 분산 특성 식을 유도하였다. 비선형 분산 특성 식을 수치해석으로 계산하기 위하여 Matlab 언어로 코드를 개발하고 유리 평판과 페놀수지 평판에 적용하여 주파수 분산 곡선을 구하였다. 또한 실험적으로 초음파 수신 신호를 받아서 단시간 주파수 분석을 함으로서 주파수에 대한 위상속도를 측정하고, 그 결과를 수치해석 결과와 비교하였다. 페놀수지는 횡적 등방성 소재이지만 실험 측정한 위상 속도는 이방성 특성을 보였다. Paper phenolic plate with transversely isotropic system is evaluated by applying elastic wave propagation. For the theoretical review of the wave propagation in the homogeneous orthotropic media, bulk waves in the unlimited system are considered and then the dispersion equation for wave propagation in plates is analytically developed. The nonlinear dispersion characteristic equation is calculated by self developed Matlab code, and applied to the isotropic glass plate and the transversely isotropic paper phenolic plate. Their results are compared to experimental measurements. Short time fourier analysis of the acquired signals from the ultrasonic sensor on the paper phenolic plate shows weak orthotropic characteristic.