• Journal of Astronomy and Space Sciences
• /
• 제13권1호
• /
• pp.79-89
• /
• 1996

We calculate the theoretical line profiles for 32 Cyg in order to investigate the influence of various velocity fields. Line profiles are calculated with wind accelerations driven by Alfven waves and described by velocity parameters. The results for Alfvenic wave model show weakened line profiles. For the orbital phases ${\Phi}$=0.78 and ${\Phi}$=0.06 the Alfvenic models show strong absorption part due to very low densities at the surface of the supergiant. Hence, we conclude the velocity gradient of the wind near the supergiant could influence on the theoretical line formation.

• 한국해안·해양공학회논문집
• /
• 제25권5호
• /
• pp.267-275
• /
• 2013

HadGEM2-AO 기후모델의 기후변화 시나리오 자료와 파랑 모델을 이용하여 기후변화에 따른 북서태평양에서의 미래 파랑 기후를 전망하였다. 21세기말 북서태평양에서 연 평균 풍속이 현재보다 낮아질 것으로 전망됨에 따라 연 평균 유의파고도 낮게 전망되었다. 현재 기후에 비해서 21세기 말 연평균 유의파고는 RCP4.5 시나리오의 경우 2~7% 감소하고, RCP8.5의 경우 4~11% 정도 감소하는 것으로 나타났다. 극한파랑의 경우도 유의파고 및 풍속이 현재에 비해서 감소할 것으로 전망되었다. 계절별로 분석한 결과 겨울철의 극한파랑은 연 극한 파랑과 비슷하게 감소하는 경향을 보인 반면, 여름철의 경우 북서태평양에서는 현재보다 증가할 것으로 나타나 미래에는 태풍의 강도가 강화 될 것으로 전망된다.

• Structural Engineering and Mechanics
• /
• 제86권6호
• /
• pp.705-714
• /
• 2023

In order to establish a dynamic model test method of bridge pylons subjected to ocean waves, the similarity method of hydroelastic model test for bridge pylons were analyzed systematically, and a model design and production method was proposed. Using this method, a dynamic test model of a bridge pylon was made, and then a free vibration test on the model structure and a dynamic response test of the model structure under wave actions were conducted in a wave flume. The results of the free vibration test show that the primary natural frequencies of the structure by the model test are close to the design frequencies of the prototype structure, indicating that the dynamic characteristics of the bridge pylon are well simulated by the model structure. The results of the dynamic response test show that wave induced base shear forces and motion responses on the model structure are consistent with the numerical results of the prototype structure. The model test results confirm that the proposed model test design method is feasible and applicable. It has application and reference significances for model testing studies of such marine bridge structures.

• 한국해안해양공학회지
• /
• 제8권3호
• /
• pp.236-245
• /
• 1996

심해파가 천이수역 또는 천해로 이동하여 올 때 수심의 변화에 의해 발생하는 파의 굴절을 울산만 해역에서 수치모델을 이용하여 분석하여 보았다. 또한 이 모델은 해안 또는 연안의 어 특정한 지점에서 풍향 및 풍속 자료를 이용하여 파랑스책트럼을 계산할 수 있으며, 이로부터 그 지점에서의 유의파고를 구할 수 있다. 본 연구에서는 임의의 일정한 풍향과 풍속을 토대로 파랑스책트럼을 계산하였으며, 그 결과를 PNJ(Pierson, Newmann and James) 계산도표 및 Bretschneider 계산도표와 비교하여 보았다. 이러한 굴절과 파랑스책트럼은 항만 선정이나 각종 해안구조물 설계 등에 있어 기초자료로 유용하게 쓰일 수 있을 것이다

• 한국해양공학회지
• /
• 제21권2호
• /
• pp.35-41
• /
• 2007

In general, coastal damage is mostly occurred by the action of complex factors, like severe water waves. If the maximum storm surge height combines with high tide, severe water waves will overflow coastal structures. Consequently, it can be the cause of lost lives and severe property damage. In this study, using the numerical model, the storm surge was simulated to examine its fluctuation characteristics at the coast in front of Noksan industrial complex, Korea. Moreover, the shallow water wave is estimated by applying wind field, design water level considering storm surge height for typhoon Maemi to SWAN model. Under the condition of shallow water wave, obtained by the SWAN model, the wave overtopping rate for the dike in front of Noksan industrial complex is calculated a hydraulic model test. Finally, based on the calculated wave-overtopping rate, the inundation regime for Noksan industrial complex was predicted. And, numerically predicted inundation regimes and depths are compared with results in a field survey, and the results agree fairly well. Therefore, the inundation modelthis study is a useful tool for predicting inundation regime, due to the coastal flood of severe water wave.

• 한국해양공학회지
• /
• 제15권3호
• /
• pp.20-27
• /
• 2001

After using the filtering method, wave parameters are calculated by the spectral analysis and wave by wave analysis. Extreme environments and higher wave characteristics int he Chujeon Sea are analyzed using the observed wave data. Higher wave has been intensely emphasized as an important environmental force parameter in several recent research works. The aims of this study are to summarize the distribution of extreme environment for wind waves, and to find occurrence probability of higher wave in Chujeon Sea. Ocean wave statistics varying with sea state are found to respond linearly to the spectral peakedness parameter Qp, mean run-length and Ursell number. Although the spreading of the field results is large, it may be concluded that the tendency of wave group formation depends on the spectral peakedness parameter Qp. Extreme wave is estimated to apply various model distribution functions by using the monthly maximum significant wave parameters which can be used to the design and analysis of coastal structures.

• 한국해양공학회지
• /
• 제22권5호
• /
• pp.1-6
• /
• 2008

A kinematics model of a ship wake in the presence of surface waves generated by wind is presented. It was found that a stationary wave structure behind a ship covered a wedge region with the angle at the top of the wake and that only divergent waves were present in a ship wake instead of both the longitudinal and cross-waves, which are known as the Kelvin model. Ship motion at some angle to wind waves can cause an essential asymmetry of the wake, compressing its windward half.

• 한국해양공학회지
• /
• 제34권5호
• /
• pp.294-303
• /
• 2020

This study discusses data collection, calculation of wind and wave-induced resistance, and speed-power analysis of an 8,600 TEU container ship. Data acquisition system of the ship operator was improved to obtain the data necessary for the analysis, which was accomplished using SPA (Ship Performance Analysis, Park et al., 2019) in conformation with ISO15016:2015. From a previous operation profile of the container, the standard operating conditions of mean draft were 12.5 m and 13.6 m, which were defined with the mean stowage configuration of each condition. Model tests, including the load-variation test, were conducted to validate new ship performance and for the speed-power analysis. The major part of the added resistance of container ship is due to the wind. To check the reliability of wind-resistance calculation results, the resistance coefficients, added resistance, and speed-power analysis results using the Fujiwara regression formula (ISO15016:2015) and Computational fluid dynamics (Ryu et al., 2016; Jeon et al., 2017) analysis were compared. Wind speed and direction measured using an anemometer were used for wind-resistance calculation and the wave resistance was calculated using the wave-height and direction-data from weather information. Also, measured water temperature was used to calculate the increase in resistance owing to the deviation in water density. As a result, the SPA analysis using measured data and weather information was proved to be valid and able to identify the ship's resistance propulsion performance. Even with little difference in the air-resistance coefficient value, both methods provide sufficient accuracy for speed-power analysis. The differences were unnoticeable when the speed-power analysis results using each method were compared. Also, speed-power analysis results of the 8,600 TEU container ship in two draft conditions show acceptable trends when compared with the model test results and are also able to show power increase owing to hull fouling and aging. Thus, results of speed-power analysis of the existing 8,600 TEU container ship using the SPA program appropriately exhibit the characteristics of speed-power performance in deal conditions.

• Wind and Structures
• /
• 제27권4호
• /
• pp.223-234
• /
• 2018

In this study, a simplified three-dimensional calculation model is developed for the dynamic analysis of soil-pile group-supertall building systems excited by wind loads using the substructure method. Wind loads acting on a 300-m building in different wind directions and terrain conditions are obtained from synchronous pressure measurements conducted in a wind tunnel. The effects of soil-structure interaction (SSI) on the first natural frequency, wind-induced static displacement, root mean square (RMS) of displacement, and RMS of acceleration at the top of supertall buildings are analyzed. The findings demonstrate that with decreasing soil shear wave velocity, the first natural frequency decreases and the static displacement, RMS of displacement and RMS of acceleration increase. In addition, as soil material damping decreases, the RMS of displacement and the RMS of acceleration increase.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제9권6호
• /
• pp.624-640
• /
• 2017

In this paper, the slamming coefficients on local members of a jacket structure under plunging breaker are studied based on numerical simulations. A 3D numerical model is used to investigate breaking wave forces on the local members of the jacket structure. A wide range of breaking wave conditions is considered in order to get generalized slamming coefficients on the jacket structure. In order to make quantitative comparison between CFD model and experimental data, Empirical Mode Decomposition (EMD) is employed for obtaining net breaking wave forces from the measured response, and the filtered results are compared with the computed results in order to confirm the accuracy of the numerical model. Based on the validated results, the slamming coefficients on the local members (front and back vertical members, front and back inclined members, and side inclined members) are estimated. The distribution of the slamming coefficients on local members is also discussed.