• 대한조선학회논문집
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• 제41권1호
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• pp.1-7
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• 2004

GUI program for analyzing directional spectrum waves is introduced in this paper Basically, MLM (Maximum Likelihood Method) was used for this program which was additionally consisted of performing spectral and time domain analysis for two dimensional irregular waves. Moreover, the directionality of directional spectrum waves generated by single summation and double summation method was investigated based on MLM. The directionality from each summation method has good agreement compared with that of target wave spreading function in the case of single wide directional spectrum waves. In addition to this, the resolution of directionality in double summation method was investigated as introducing coherence function between each wave component

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.377-380
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• 2002

This paper presents the results of a study investigating methods of interpretation of wave directionality based on wavelet transforms. Two-dimensional discrete wavelet was used for the analysis. The proposed scheme utilizes a single frame of ocean waves to detect their directionality. This fact is striking considering the fact that traditional methods require long time histories of ocean wave elevation measured at various locations. The developed schemes were applied to the data generated from numerical simulations and video images to test the efficiency of the proposed scheme in detecting the directionality of ocean waves.

• 한국해안해양공학회지
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• 제13권2호
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• pp.139-148
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• 2001

파랑에 관계하는 현상에는 월파, 표사이동, 구조물의 진동.동요, 파괴 등 방향성의 영향을 현저하게 받아들이는 것이 많다. 이들은 비선형성이 강하기 때문에 수치계산에 의한 해석이 곤란하므로, 수리모형실험으로 외력인자를 평가, 해석정도를 높일 필요성이 증대하고 있다. 본 연구는 파랑의 다양한 입사각에 따라 사석방파제의 안정성을 논의하였으며, 파괴율은 방향성규칙파에서 $30^{\circ}$, 방향성불규칙파인 경우는 40$^{\circ}$부근에서 입사각 $0^{\circ}$일 때 보다 상대적으로 크게 변동하였다. 즉, 사석방파제의 안정성에 미치는 방향성효과에 따른 것이라고 평가할 수 있다. 이들은 1/10 최대 합성유속의 방향별 빈도분포의 피크가 $20^{\circ}$~$40^{\circ}$에서 발생하는 사실과 부합된다.

• Ocean and Polar Research
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• 제25권4호
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• pp.437-446
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• 2003

Field measurements of directional waves were carried out during the summer of 2002 at two coastal sites in water of finite depth. A couple of general purpose instruments were used employing acoustic Doppler technology. The aim of the study was to investigate the spatial behavior of the directional movement of waves as they come ashore. In total,74 tests were carried out during which sea states of low to moderate intensity were recorded. A great number of these runs displayed bimodal characteristics of the spreading function at high frequencies. It was found that in general, the frequency-integrated directional width tends to broaden as the water shoals and when refraction effects are negligible. This is attributed to wave-wave interactions that become pronounced in shallow water. The same directional width showed, also, a tendency to increase with increasing peak frequency of the sea state spectrum. The behavior of the kurtosis of the spreading function was also examined. It was found that for higher frequencies this index tends to increase in wave spectra above a certain sea severity threshold.

• 해양환경안전학회지
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• 제28권5호
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• pp.700-711
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• 2022

본 연구에서는 칠발도, 거문도, 동해에서 20년 이상 관측된 파랑자료를 16 방위별 극치확률분석을 통해 재현빈도별 심해설계파를 산정하였고, 이 값을 방향을 고려하지 않은 전방향파의 심해설계파와 비교하였다. Weibull 분포함수를 확률분포함수로 사용하였으며, 최소자승법을 사용해서 매개변수를 결정하였다. 추정된 분포함수는 Kolmogorov-Smirnov 방법을 사용하여 적합도를 검증하였다. 그 결과 방향별로 구한 심해설계파가 전방향파의 심해설계파보다 모든 방향에서 상대적으로 작은 것으로 나타났다. 파향별로 구한 50년 빈도 설계파고는 칠발도, 거문도, 동해에서 각각 7.46 m(NNE), 12.05 m(S), 9.69 m(SSW)가 최대값이지만, 전방향파로 구한 설계파고는 각각 7.91 m, 13.82 m, 10.38 m이었다. 이는 현재 해양 및 연안 구조물 설계에 사용하고 있는 16 방위별 심해설계파고가 과소산정되었을 가능성이 있음을 보여준다.

• 한국해양공학회지
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• 제11권4호
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• pp.76-89
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• 1997

The hydrodynamic interaction characteristics between multiple floating bodies of semisubmersible type are examined to present the basic data for the design of huge offshore structures supported by a large number of the floating bodies in multi-directional irregular waves. The numerical approach is based on a combination of a three-dimensional source distribution method, the wave interaction theory and the spectral analysis method. The effects of wave directionality on the wave exciting forces acting on multiple floating bodies in multi-directional irregular waves also have been pointed out.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제6권1호
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• pp.1-6
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• 2003

This study presents the results of series of studies, which are mainly devoted to the application of wavelet transforms to various problems in ocean engineering. Both continuous and discrete wavelet transforms were used. These studies attempted to solve detection of wave directionality, detection of wave profile, and decoupling of the rolling component from free roll decay tests. The results of these analysis, using wavelet transform, demonstrated that the wavelet transform can be a useful tool in analyzing many problems in the filed of ocean engineering.

• 한국해양공학회지
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• 제17권3호
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• pp.1-6
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• 2003

This study presents the results of series of studies, which are mainly devoted to the application of wavelet transforms to various problems in ocean engineering. Both continuous and discrete wavelet transforms were used. These studies attempted to solve detection of wave directionality, detection of wave profile, and decoupling of the rolling component from free roll decay tests. The results of these analysis, using wavelet transform, demonstrated that the wavelet transform can be a useful tool in analyzing many problems in the filed of ocean engineering.

• International Journal of Ocean System Engineering
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• 제2권4호
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• pp.250-258
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• 2012

The distribution of wave heights is assumed to be a Rayleigh distribution, based on the assumption of a narrow band and Gaussian distribution of wave elevation. The present study was started with doubts about the narrow band assumption. We selected the wave spectra widely used to simulate irregular random waves. The wave spectra used in this study included the Pierson-Moskowitz spectrum, Bretschneider-Mitsuyasu spectrum, and JONSWAP spectrum. The directionality of the waves was considered. The cosine 2-l type directional spreading function and mixed form of the half-cosine 2-s type with Mitsuyasu type directional spreading are considered here to investigate the effects of a directional spreading function on random waves. The simulated wave height distribution is compared with a Rayleigh distribution.

• 한국해양공학회지
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• 제8권1호
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• pp.23-32
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• 1994

A numerical procedure is described for simultaneously predicting the motion and structural responses of tension leg platforms (TLPs) in multi-directional irregular waves. The developed numerical approach is based on a combination of a three dimensional source distribution method, the finite element method for structurally treating the space frame elements and a spectral analysis technique of directional waves. The spectral description for the linear responses of a structure in the frequency domain is sufficient to completely define the responses. This is because both the wave inputs and the responses are stationary Gaussian ran dom process of which the statistical properties in the amplitude domain are well known. The hydrodynamic interactions among TLP members, such as columns and pontoons, are included in the motion and structural analysis. The effect of wave directionality has been pointed out on the first order motion, tether forces and structural responses of a TLP in multi-directional irregular waves.