• 한국해양공학회지
• /
• 제13권1호통권31호
• /
• pp.113-120
• /
• 1999

In this paper, mathematical formulation of the high-order spectral/boundary-element method is shown. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated in time-domain. Three-dimensional waves generated by a uniformly translating suriace pressure are calculated and discussed. The obtained results are compared with others results, The comparisons show good agreements.

• 한국수자원학회논문집
• /
• 제30권3호
• /
• pp.225-233
• /
• 1997

부체의 장주기동요, 연안구조물과 계류선의 파괴 등과 같은 역기능으로 인해 파군현상의 정확한 해석은 시급한 과제라 하겠다. 본고에서는 연안계에서 발생하는 파랑과 가장 근접한 비선형불규칙 파랑계를 산정하여 해안구조물의 피로거동에 지대한 영향을 미치는 파군당 파랑의 수와 해안구조물의 first excursion failure mode를 결정하는 high run에서의 파랑수를 중심으로 파군현상을 해석하였다. 해석과정에 mapping technique과 유의파경사를 perturbation parameter로 섭동이론이 사용되었다. 해석결과 Gaussian wave계에서 균등분포하는 것으로 알려진 위상함수는 평균값 주위에 집중분포하였고, 그 정도는 비선형성이 증가할수록 심화되었다. threshold crossing rate의 경우 비선형성이 심화될수록 평균해수위보다 큰 쪽으로 분포형이 이동하였으며 파군당 파랑수와 high run에서의 파랑수도 비슷한 경향을 보여 최근 설치범위가 심해쪽으로 확대되는 해안구조믈의 경우 피로거동에 대한 보강이 요만된다.

• 한국해안·해양공학회논문집
• /
• 제28권4호
• /
• pp.212-221
• /
• 2016

본 연구에서는 동해안에 고파가 내습한 시점을 대상으로 관측 파랑자료와 미국 국립해양대기청(NOAA)에서 추산한 기상 예측자료를 통합 분석하였으며, 기상예측자료를 이용한 동해안 파랑예측시스템을 구축하였다. 또한, 파랑 예측결과를 관측자료와 비교하여 적용성을 확인하였다. 동해안 연안에는 2회 파고가 증가하고 2차 파고 증가 시 연안 기상조건은 양호한 경우도 있어 피해가 우려된다. 2008년 2월에 관측된 파랑 관측자료를 이용하여 고파의 전파방향을 추정하였으며, 기상자료와 비교를 통해 2번째 증가시기 파랑의 발생역이 동해 연안에서 멀리 떨어진 러시아와 일본 사이 해역임을 확인하였다.

• 한국연안방재학회지
• /
• 제4권1호
• /
• pp.7-19
• /
• 2017

In this study, waves and currents observed by acoustic AWAC, VECTOR and Aquadopp Profiler in Anmok coastal waters were analysed to account for the variability of wave and current and to understand the mechanism of sediment transport generated by wave-induced current in the surf-zone. The monthly variation of wave and residual currents were analysed and processed with long-term observed AWAC data at station W1, located at the water depth of about 18m measured during from February 2015 to September 2016. Wave-induced currents were also analysed with intensive field measurements such as wave, current, suspended sediment, and bathymetry data observed at the surf-zone during in winter and summer. The statistical result of wave data shows that high waves coming from NNE and NE in winter (DEC-FEB) are dominant due to strong winds from NE. But in the other season waves coming from NE and ENE are prevalent due to the seasonal winds from E and SE. The residual currents with southeastern direction parallel to the shoreline are dominant throughout a year except in winter showing in opposite direction. The speed of ebb-dominant southeastern residual currents decreasing from surface to the bottom is strong in summer and fall but weak in winter and spring. By analysing wave-induced current, we found that cross-shore current were generated by swell waves mainly in winter with incoming wave direction about $45^{\circ}$ normal to the shoreline. Depending on the direction of incoming waves, longshore currents in the surf-zone were separated to southeastern and northwestern flows in winter and summer respectively. The variation of observed currents near crescentic bars in the surf-zone shows different direction of longshore and cross-shore currents depending on incoming waves implying to the reason of beach erosion generating the beach cusp and sandbar migration during high waves at Anmok.

• 한국조경학회지
• /
• 제31권4호
• /
• pp.49-56
• /
• 2003

This study is to find physiological effects of acoustic information on landscape preference. Both the volume and the rate of $\alpha$-waves and $\beta$-waves were used to measure the effects in the study. The result of this study are summarized as follows: The outputting amount of $\alpha$-waves are sorted by different types of visual and acoustic factors. The results show that acoustic factors interacted with visual factors. That is, although visual factors are positive, the volume of $\alpha$-waves depends upon the character of acoustic factors; positive acoustic factors produce more $\alpha$-waves than negative or neutral(soundless) acoustic factors. Also the volume of $\alpha$-waves increase in the case of positive acoustic factors even if there is the same negative visual information. The results show that the volume of $\alpha$-waves increase without connecting with the types of visual factors. The volume of $\beta$-waves are largely reduced when visual stimulus is positive and soundless stimulus is provided. On the other hand, they generally increase when both visual and acoustic stimuli are negative, which fosters extremely unstable, tense and upset stress. The rate of $\alpha$-waves increase according to supplying positive acoustic factors in the opposed visual factors. The rate of wave(shouldn't be $\alpha$-waves\ulcorner) is high if both visual and acoustic factors are positive, so it is the most comfortable and causes no stress. Preference is the lowest if visual and acoustic factors are negative, but a -waves are conspicuously low in positive visual and negative acoustic factors.

• 한국해양공학회지
• /
• 제12권2호통권28호
• /
• pp.33-42
• /
• 1998

In the presence of incident waves with different frequencies, the second order sum and difference frequency waves due to the nonlinearity of the incident waves come into existence. Although the magnitudes of the forces produced on a Tension Leg Platform(TLP) by these nonlinear waves are small, they act on the TLP at sum and difference frequencies away from those of the incident waves. So, the second order sum and difference frequency wave loads produced close to the natural frequencies of TLPs often give greater contributions to high and low frequency resonant responses. The second order wave exciting forces and moments have been obtained by the method based on direct integration of pressure acting on the submerged surface of a TLP. The components of the second order forces which depend on first order quantities have been evaluated using the three dimensional source distribution method. The numerical results of time domain analysis for the nonlinear wave exciting forces in regular waves are compared with the numerical ones of frequency domain analysis. The results of comparison confirmed the validity of the proposed approach.

• 한국해양공학회지
• /
• 제16권4호
• /
• pp.7-12
• /
• 2002

This study is aimed to find the scouring mechanism at the toe of rubble mound structures. To investigate the characteristics of scouring in front of the structure, experiments were performed with regular waves in a 2-D flume. The results of this study are as follows. 1) It can be said the characteristics of incident wave causes rolling and sliding of armour block. The difference of wave pressure on the slope, internal flow as well as settlement of armour block due to the weight cause scouring. 2) It is observed that scouring depth at the toe increased when wave height or period increased. The location of ultimate scouring and deposition depth moved seaward when wave period increased. 3) The failure of rubble mound structure was caused by waves or scouring. Failure by erosion increased with high waves and long waves. 4) Using surf-similarity parameter including characteristics of incident waves and structure, scouring and deposition pattern were found and their limit was formulated.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
• /
• pp.253-257
• /
• 2003

Theoretical-numerical analysis of wave instability is conducted with parametric response function model. Fluctuating instantaneous mass evaporation rate functionally coupled with pressure perturbations with phase lag is assumed to examine the validity of the method. With sufficiently large amplitude and less phase lag to perturbation, combustion response is resonant to pressure waves, unstable waves are amplified, and the system is driven to instability. Magnitude of response is a crucial instability parameter in the determination of a stability margins and makes a critical change of balancing conditions between the amplifying and damping acoustic energies. In the phase regime the unstable waves are amplified, whereas, the acoustic waves are attenuated in the out-of-phase regime. In the intermediate regime, no distinct tendency of unstable waves was determined.

• 한국해안·해양공학회논문집
• /
• 제26권3호
• /
• pp.149-159
• /
• 2014

본 연구에서는 속초 인근의 파향 파고계로 관측된 파랑 자료를 이용하여 동해안 주요지역에 너울성 고파를 예측하는 알고리즘을 개발하였다. SWAN 모형을 이용하여 연안의 파랑 관측 자료로부터 고파 발생지로 예상되는 외해지점의 파랑 제원을 추정하였다. 추정된 파랑 제원을 경계조건으로 쓰고 SWAN 모형과 파향선 추적법을 사용하여 동해안 주요지역에서의 너울성 고파를 예측하였다. 왕돌초에서 관측한 파랑 자료를 예측 결과와 비교하여 예측알고리즘의 정확성을 검증하였다. 동해안 실시간 파랑관측 시스템과 본 연구결과를 활용하면 동해안 너울성 고파를 보다 정확하게 예측할 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제5권1호
• /
• pp.161-177
• /
• 2013

High-speed vessels require good resistance and seakeeping performance for safe operations in rough seas. The resistance and seakeeping performance of high-speed vessels varies significantly depending on their hull forms. In this study, three planing hulls that have almost the same displacement and principal dimension are designed and the hydrodynamic characteristics of those hulls are estimated by high-speed model tests. All model ships are deep-V type planing hulls. The bows of no.2 and no.3 model ships are designed to be advantageous for wave-piercing in rough water. No.2 and no.3 model ships have concave and straight forebody cross-sections, respectively. And length-to-beam ratios of no.2 and no.3 models are larger than that of no.1 model. In calm water tests, running attitude and resistance of model ships are measured at various speeds. And motion tests in regular waves are performed to measure the heave and pitch motion responses of the model ships. The required power of no.1 (VPS) model is smallest, but its vertical motion amplitudes in waves are the largest. No.2 (VWC) model shows the smallest motion amplitudes in waves, but needs the greatest power at high speed. The resistance and seakeeping performance of no.3 (VWS) model ship are the middle of three model ships, respectively. And in regular waves, no.1 model ship experiences 'fly over' phenomena around its resonant frequency. Vertical accelerations at specific locations such as F.P., center of gravity of model ships are measured at their resonant frequency. It is necessary to measure accelerations by accelerometers or other devices in model tests for the accurate prediction of vertical accelerations in real ships.