• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.498-504
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• 2016

In this study, to predict the effect of beach nourishment at Haeundae Beach, the waves and wave-induced currents were compared before and after beach nourishment using the XBEACH model. Representative wave conditions were determined for the data observed during 2014 (KHOA). Then, the Hs,max and Hs,1/10 values, and their prevalent directions, were used in the numerical modeling input data. A variable grid system was used for the $5km{\times}2.5km$ model areas, and irregular waves based on the JONSWAP spectrum were given as incident wave conditions. In the summer season, eastward wave-induced currents were developed along the beach by the incident wave direction. Before the beach nourishment, the maximum speed around the surf zone was 1.2-1.5 m/s in the central zone of the beach, whereas the maximum speed increased to 1.4-1.6 m/s at the same areas when the currents toward Mipo Harbor were blocked as an effect of the groins after the beach nourishment. In the winter season, westward wave-induced currents were developed along the beach by the incident wave direction. After the beach nourishment, the maximum current speed increased slightly around the surf zone in the central area of the beach, and the littoral current speed decreased at the submerged breakwaters located at Dongbaek Island. As a result, after the beach nourishment, the maximum wave-induced currents increased about 10% in the surf zone of the central area of the beach.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.177-187
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• 2022

This study estimates the design wave in the event of a typhoon attack at Busan new port using the wind field, the revised shallow water design wave estimation method proposed by the Ministry of Oceans and Fisheries in 2020, and proposed a reliable method of calculating the shallow water design through verification with the wave observation data. As a result of estimating typhoon wave using the wind field and SWAN numerical model, which are commonly used in the field work, for typhoon that affected Busan new port, it was found that reproducibility was not good except typhoons KONG-REY(1825) and MAYSAK(2009). In particular, in the case of typhoon MAEMI(0314), which had the greatest impact on Busan new port, the maximum significant wave height was estimated to be about 35.0% smaller than that of the observed wave data. Therefore, a plan to improve the reproducibility of typhoon wave was reviewed by applying the method of correcting the wind field and the method of using the Boussinesq equation numerical model, respectively. As a result of the review, it was found that the reproducibility of the wind field was not good as before when the wind field correction. However as a method of linking wind field data, SWAN model results, and Boussinesq numerical model, typhoon wave was estimated during typhoon MAEMI(0314), and the maximum significant wave was similar to the wave observations, so it was reviewed to have good reproducibility.

• Korean Journal of Hydrosciences
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• v.2
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• pp.85-98
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• 1991

This paper is focused on the development of the RIVNET1 model, which is a dynamic wave model, for flood analysis in dendritic river networks with arbitrary cross-sections. This model adopted the $-point implicit RDM and utilized a relaxation algorithim in order to solve the governing equations. The double-sweep method was used to reduce the C.P.U. time to solve the matrix system of the model. This model is applied the analyze flood waves of the Ohid river in the U.S.A. and the Keum river in Korea. The results of analysis obtained from this model are compared with those of the DWOPER and observed data.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.134-139
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• 2012

This study observed downward long and short-wave radiant environment with selecting 4 areas which have different height in downtown and 1 suburban area to figure out the characteristic of radiant environment in each altitude. The purpose of this study is to collect the preliminary data for interpreting urban thermal environment in summer season by analyzing thermal characteristic of atmosphere in the upper of downtown. The results of this study are as follows. 1) The higher altitude has the lower temperature, and temperature difference was more huge in day time than night time. 2) The short wave radiation according to altitude was higher as altitude was high. 3) Generally, the higher altitude has the lower air temperature, and also the higher altitude has the lower downward long wave radiation by the atmospheric radiation. 4) The ratio short wave radiation of long wave radiation was lower as altitude was high. And the urbanization effect was higher as the ratio was low.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.4
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• pp.312-319
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• 2016

Measured wave data covering two years simultaneously at 3 locations along the eastern Arabian Sea reveals the presence of long-period (peak wave period > 18 s) low-amplitude waves (significant wave height < 1 m) and the characteristics of these waves are described in this article. In a year, 1.4-3.6% of the time, the low-amplitude long-period swells were observed, and these waves were mainly during the nonmonsoon period. The wave spectra during these long-period swells were multi-peaked with peak wave period around 18.2 s, the secondary peak period around 13.3 s and the wind-sea peak period at 5 s. The ratio of the spectral energy of the wind-sea peak and the primary peak (swell) was slightly higher at the northern location (0.2) than that at the southern location (0.15) due to the higher wind speed present at the northern location.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.329-335
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• 2007

The eye measurement to observe the sea surface condition and estimate the wave height has been used in the open sea or the ship. The experts in the eye estimation can measure the wave height very accurately. The Beaufort wind scale is most widely used as a standard index of the eye measurement. However, more definite reference data such as the representative images by each wave heights must be necessary because the appearances and explanations in the Beaufort wind scale are not enough to understand the sea surface condition far the researcher and the public. The modern field data acquisition technique has been developed to measure wave heights, ocean weather data and even images of the sea surface in real-time. In this study, the wireless field image transmitting system for wave heights and images is installed in the real-time ocean measurement system of Chodo light tower near Sokcho city in South Korea. The wave heights and surface images acquired from the real time system in the field are compared with explanations of the Beaufort wind scale. The wave heights and images measured with the precision ultrasonic wave sensor and the scientific sea surface image transmitting system should be helpful to obtain more precise and definite information than the data from the Beaufort wind scale.

• Journal of Astronomy and Space Sciences
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• v.23 no.3
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• pp.209-216
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• 2006

Ion acoustic solitary wave in a plasma consisting of electrons and ions with an external magnetic field is reinvestigated using the Sagdeev's potential method. Although the Sagdeev potential has a singularity for n < 1, where n is the ion number density, we obtain new solitary wave solutions by expanding the Sagdeev potential up to ${\delta}n^4$ near n = 1. They are compressiv (rarefactive) waves and shock type solitary waves. These waves can exist all together as a superposed wave which may be used to explain what would be observed in the solar wind plasma. We compared our theoretical results with the data of the Freja satellite in the study of Wu et al. (1996). Also it is shown that these solitary waves propagate with a subsonic speed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.91-98
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• 1999

In this study a modified ground strain model is developed for an equivalent earthquake load and is applied to the seismic analysis of buried pipelines, The ground strain can be obtained using the ratio of a maximum ground velocity to a wave propagation velocity. To reflect soil conditions and seismic characteristics the wave propagation velocity is evaluated by a proposed dispersion curve based on wave energy distribution. In order to verify the procedures the observed earthquake data and the results of this study are compared. For the application of an equivalent earthquake load to the seismic analysis the buried pipelines are modeled using the beam theory. the results of the analyses are compared with those of a dynamic analysis code and those obtained from the response displacement method. Finally various parametric studies considering different soil conditions and seismic loads are examined.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.869-875
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• 2016

The purpose of this study is to analyze the long-term wave characteristics and tendencies of coastal waters near Korea based on wave hind-casting modelling. Wave hind-casting modelling was performed with a wind data set from ECMWF (2001~2014), which provides data from 1979 to the present. The results of numerical modelling were verified with observed data collected using wave buoys installed by the Korea Meteorological Administration (KMA) and Korea Hydrographic and Oceanographic Agency (KHOA) in offshore waters. The results agreed well with observations from buoy stations, especially during event periods such as typhoons. The quantitative RMSE value was 0.5 m, which was significant. Consequently, the results of a wave tendency analysis for 14 years (2001~2014) showed an increased appearance ratio for waves of more than 2 m in height at all regional domains. The mean appearance ratio was 0.082 % per year, which implies that coastal waves have been increasing continuously. This coastal wave tendency analysis data can be used to evaluate coastal vulnerability due to recent climate change and the design of coastal erosion prevention structures.

• Proceedings of the KSRS Conference
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• v.1
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• pp.390-393
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• 2006

It is well known that synthetic aperture radar (SAR) provides information on ocean winds and surface waves. SAR data are of particularly high value in extreme weather conditions, as radar is able to penetrate the clouds providing information on different ocean surface processes. In this presentation some recent results on SAR observation of extreme wind and ocean wave conditions is summarised. Particular emphasize is put on the investigation of typhoons and extratropical cyclones in the North Pacific. The study is based on the use of ENVISAT ASAR wide swath images. Wide swath and scansar data are well suited for a detailed investigation of cyclones. Several examples like, e.g., typhoon Talim will be presented, demonstrating that these data provide valuable information on the two dimensional structure of the both the wind and the ocean wave field. Comparisons of the SAR observation with parametric and numerical model data will be discussed. Some limitations of standard imaging models like, e.g., CMOD5 for the use in extreme wind conditions are explained and modifications are proposed. Finally the study summarizes the capabilities of new high resolution TerraSAR-X mission to be launched in October 2006 with respect to the monitoring of extreme weather conditions. The mission will provide a spatialresolution up to 1m and has full polarimetric capabilities.