• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.4
• /
• pp.365-373
• /
• 2011

Damage of reinforced concrete panel subjected to blast load using parallel and domain decomposition is analyzed. The numerical results are sensitive to the mesh size because blast waves are generated during the extremely short term. In order to investigate the effect of mesh size on the blast wave, the analysis results from various wave mesh size using AUTODYN, the explicit finite element analysis program, were compared with existing experimental results. The smaller mesh size was, the higher accuracy was. However, in this case, the analysis was inefficient. Therefore, in order to increase numerical efficiency, the parallel analysis using decomposed method based on Euler and Lagrangian description was performed. Finally, the decomposed method using both the structure domain based on Lagrange description and the blast wave domain based on Euler description was more efficient than the decomposed method using only the Lagrange mesh on structure domain.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.25 no.5
• /
• pp.335-347
• /
• 2013

In February 2008, high storm waves due to a developed atmospheric low pressure system propagating from the west off Hokkaido, Japan, to the south and southwest throughout the East Sea (ES) caused extensive damages along the central coast of Japan and along the east coast of Korea. This study consists of two parts. In the first part, we estimate extreme storm wave characteristics in the Toyama Bay where heavy coastal damages occurred, using a non-hydrostatic meteorological model and a spectral wave model by considering the extreme conditions for two factors for wind wave growth, such as wind intensity and duration. The estimated extreme significant wave height and corresponding wave period were 6.78 m and 18.28 sec, respectively, at the Fushiki Toyama. In the second part, we perform numerical experiments on wave-structure interaction in the Fushiki Port, Toyama Bay, where the long North-Breakwater was heavily damaged by the storm waves in February 2008. The experiments are conducted using a non-linear shallow-water equation model with adaptive mesh refinement (AMR) and wet-dry scheme. The estimated extreme storm waves of 6.78 m and 18.28 sec are used for incident wave profile. The results show that the Fushiki Port would be overtopped and flooded by extreme storm waves if the North-Breakwater does not function properly after being damaged. Also the storm waves would overtop seawalls and sidewalls of the Manyou Pier behind the North-Breakwater. The results also depict that refined meshes by AMR method with wet-dry scheme applied capture the coastline and coastal structure well while keeping the computational load efficiently.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 1993.07a
• /
• pp.175-177
• /
• 1993

열대성 저기압에 의해 발생되는 태풍 또는 폭풍은 주변해역에 평균수위상승(setup)을 유발하며 진행하게 된다. 우리나라에는 주로 하절기에 남해평양에서 발생한 해풍의 영향을 받아 해일 등의 피해를 입게 되는데, 이러한 해일은 여러가지 수위상승효과가 복합된 결과이다. 즉, 폭풍 도착전 발생하는 초기수위상승(initial setup), 저기압 중심 주변의 급격한 압력경사에 의한 수위상승(pressure setup), 폭풍의 진행속도가 발생된 파의 속도에 근접할 경우 압력차에 의한 수위상승이 더욱 증폭되는 장파수위상승(long wave setup), 바람과 바닥 마찰에 의한 수위상승(wind and bottom stress setup), Coriolis힘에 의한 수면상승(Coriolis setup) 등 여러 가지 효과에 의해 해일이 발생하게 된다. (중략)

• Proceedings of the Korean Society of Disaster Information Conference
• /
• 2015.11a
• /
• pp.278-279
• /
• 2015

최근 해수욕장, 저지대 침식, 해안시설물 노후화 등과 같이 해안지역 구성 및 지형적 요인에 따라 국지적으로 발생하는 피해와 태풍 및 이상너울 등의 대규모 기상현상에 의해 해안재난이 발생가능성이 높아지고 실제 발생하는 실정이다. 본 논문에서는 재난대응을 위한 과학적 재난정보 수집 및 분석을 통해 의사결정에 활용하고 효과적으로 예방 대응하고자 유관기관에서 다양하게 구축된 시스템의 재난관련 자료를 수집하였으며, 태풍 내습시 신속한 대응을 위해 폭풍해일 시뮬레이션을 통해 범람파고를 추정하였다. 기존 상황판단을 위한 정보수집단계에 추가적으로 관측자료 및 시뮬레이션을 통한 정량적 피해추정정보를 신속하게 제공함으로서 재난상황판단을 가능할 수 있도록 방안을 마련하였다.

• Journal of the Korean earth science society
• /
• v.30 no.2
• /
• pp.196-209
• /
• 2009

Occurrences of sandstorms in the deserts and loess of Mongolia and northern China and associated dustfall episodes in the Korean Peninsula were monitored during the period January through December, 2005. False colour images were made by directly receiving the NOAA Advanced Very High Resolution Radiometer (AVHRR) data, and the distribution and transport of sandstorms were analyzed. The ground concentrations for PM10, PM2.5 and visibility of the dustfall episodes (PM10 concentration over $190{\mu}g\;m^{-3}$) were analyzed at Cheongwon, located midway in South Korea, and in the leeward direction of the place of origin of the sandstorms. Variations in the concentrations of $O_3,\;NO_2$, CO and $SO_2$ were also compared with dust concentrations in the dustfall episodes. Fewer occurrences of strong sandstorms in the place of origin were observed in 2005, due largely to the accumulation of snow and mild fluctuations of high and low pressure systems in the place of origin, thereby accounting for a low frequency of dustfall episodes in Korea, compared with those during the period 1997-2005. A total of 7 dustfall episodes were monitored in Korea in 2005 that lasted 11 days. In summer, sandstorms occurred less frequently in the source region in 2005 due to high humidity and milder winds, thereby causing no dustfall episodes in Korea. In case the sandstorms occurring at the place of source head directly to Korea without passing through large cities and industrial areas of China, the PM2.5 concentrations were measured at 20% or lower than the PM10 concentrations. However, when the sandstorms headed to Korea via the industrial areas of eastern China, where they pick up anthropogenic air pollutants, the PM2.5 concentrations were at least 25% higher of the PM10 concentrations. On the other hand, over 5 cases were observed and analyzed in 2005 where the PM10 concentrations of sand dust originating from the deserts were measured at $190{\mu}g\;m^{-3}$ or lower, falling short of the level of a dustfall episode.

• 어항어장
• /
• s.10
• /
• pp.14-19
• /
• 1990

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.26 no.5
• /
• pp.292-299
• /
• 2014

Since most of the researches on the coastal inundation due to typhoons have considered only storm surges, an additional inundation due to rainfall has been neglected. In general, typhoons are natural disasters being accompanied by the rainfall. Thus, it is essential to consider the effect of rainfall in the numerical simulation of coastal inundation due to storm surges. Because the rainwater is discharged to the sea through the storm sewer system, it should be included in the numerical simulation of storm surges to obtain reasonable results. In this study an algorithm that can deal with the effects of rainfall and sewer system is developed and combined with a conventional storm surge numerical model. To test the present numerical model various numerical simulations are conducted using the simplified topography for the cases including the inundation due to rainfall, the drainage of rainwater, the backflow of sea water, and the increase of sea water level due to drainage of rainwater. As a result, it is confirmed that the basic performance of the present model is satisfactory for various flow situations.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.2
• /
• pp.333-342
• /
• 2017

In order to understand the mechanism of the cross-shore evolution of storm (barred) and normal (nonbarred) profiles of a sandy beach, the vertically two-dimensional laboratory experiment was performed with a movable bed. The beach profiles and free surface motion were measured under monochromatic wave conditions evolving the storm and normal beach profiles. The observation was conducted in the surf zone during the alternation of the two wave conditions to reach its quasi-equilibrium state. The sandbar-crest and trough and the steep berm were evolved due to the plunging breakers in the storm case, and the bar-trough was decayed due to the spilling breakers in the normal case. From the measurements, it was found that the storm wave case was in an erosion state and the normal wave case was in an accretion state. The strong undertow, which is a dominant factor of the offshore migration mechanism, was developed in the storm wave case, and the weak undertow was developed in the normal wave case. The skewness and the asymmetry of the nonlinear wave motion, which is a dominant factor of the onshore migration mechanism, was measured similarly in both cases.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.4
• /
• pp.467-478
• /
• 2009

The super-geomagnetic storms called 2003 Halloween event globally occurred during the period of 29 through 31 which are the following days when the solar flares of X18 class exploded on 28 October 2003. The S4 index from GPS signal strength and the peak electron density ($NmF_2$) from GPS tomography method are analyzed according to the date. The occurrences of the cycle slip and scintillation in the GPS signals are 1,094 and 1,387 on 28 and 29 October, respectively and these values are higher than 604 and 897 on 30 and 31 October. These mean the ionospheric disturbances are not always generated by the period of geomagnetic storm. Therefore, GPS S4 index is useful to monitor the ionospheric disturbances. Behaviors of ionospheric electron density estimated from GPS tomography method are analyzed with the date. At UT = 18 hr, the maximum $NmF_2$ is shown on 28 October. It agrees with $NmF_2$ variation measured from Anyang ionosonde, and the GPS signal are better condition on 30 and 31 October than 28 October. In conclusion, GPS signal condition is relation with geomagnetic activities, and depend upon the variation of the electron density. We will study the long-term data to examine the relationship between the GPS signal quality and the electron density as the further works.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.30 no.2
• /
• pp.69-83
• /
• 2018

The South China Sea (SCS) is a typical marginal sea characterized with the deep basin, shelf break, shallow shelf, many straits, and complex bathymetry. This study investigated the tidal characteristics and propagation, and reproduced typhoon-induced storm surge in this region using the regional real-time tide-surge model, which was based on the unstructured grid, resolving in detail the region of interest and forced by tide at the open boundary and by wind and air pressure at the surface. Typhoon Haiyan, which occurred in 2013 and caused great damage in the Philippines, was chosen as a case study to simulate typhoon's impact. Amplitudes and phases of four major constituents were reproduced reasonably in general, and the tidal distributions of four constituents were similar to the previous studies. The modelled tide seemed to be within the acceptable levels, considering it was difficult to reproduce the tide in this region based on the previous studies. The free oscillation experiment results described well the feature of tide that the diurnal tide is prevailing in the SCS. The tidal residual current and total energy dissipation were discussed to understand the tidal and sedimentary environments. The storm-surge caused by typhoon Haiyan was reasonably simulated using this modeling system. This study established the regional real-time barotropic tide/water level prediction system for the South China Sea including the seas around the Philippines through the validation of the model and the understanding of tidal characteristics.