해운대 해빈에서 특정 외력하의 표사이동 특성

김권수(Gweon-Su Kim),유하상(Ha-Sang Ryu),박형수(Hyoung-Su Park),김강민(Kang-Min Kim) 한국항해항만학회 2013 한국항해항만학회지 Vol.37 No.6

해운대 해수욕장은 육지로부터 유입되는 모래 공급원의 감소와 고파랑 및 반사파 등의 영향으로 백사장의 폭이 매년 감소하는 것으로 나타났다. 표사이동에 따른 해빈변형 문제를 해결하기 위해서는 해빈류의 특성을 예측할 필요가 있다. 본 연구에서는 해운대 해수욕장에 대한 장기적이고 종합적인 관측자료를 바탕으로, 계절별 대표파랑과 이상파에 대한 해빈류 및 표사이동 수치실험을 실시하였다. 여름에는 평상파 및 S계열 파랑에 의해서 해빈류는 연안을 따라 동쪽으로 흘러 미포측에서 퇴적되는 양상을 보이고, 겨울에는 평상파 및 E 계열의 파랑에 의해 해빈류는 서향하여 동백섬 인근에서 퇴적양상을 보이고 있다. 50년빈도 고파랑 내습시 SSW 파랑은 해운대 중앙에서 이안류가 발생하고, ESE 파랑은 미포측에서 연안을 따라 서측으로 흐름을 발생시키는 것으로 나타났다. The width of Haeundae beach has been decreasing annually due to the loss of sand from land, high waves, reflected waves, etc.. The accurate prediction of wave-induced currents is indispensible to analyze the beach deformation due to the sediment transport. In the this study, Numerical experiments were performed with seasonal representative wave on the basis of a long term and comprehensive survey data. In summer, we found the deposition of Mipo by longshore current eastly by ordinary and S waves, and in winter, the deposition of Dongback-island by longshore current westly by ordinary and E waves. In addition, rip current occurs in the middle of Haeundae beach by 50 year return period wave and current westly along the coast by ESE directional wave.

마산만 재해방지시설을 이용한 해수교환 방안에 관한 연구

김권수(Gweon-Su Kim),유하상(Ha-Sang Ryu),김강민(Kang-Min Kim) 한국항해항만학회 2013 한국항해항만학회지 Vol.37 No.6

마산만은 반폐쇄성 해역으로, 느린 유속과 육상오염물질의 하천부하 등으로 인해 심각한 수질문제를 가지고 있으며, 동시에 폭풍해일에 취약한 입지적 특성을 나타내고 있다. 이 중 폭풍해일 저감대책으로 제시된 재해방지시설을 운용함과 동시에 이를 마산만 내측 수질개선에 활용하는 방안을 모색하였다. 즉, 재해방지시설을 가동하여 마산만 내측과 외측의 수위조건이 다를 때 발생하는 수두차를 이용하여 만 내ㆍ외의 해수를 교환하였다. 재해방지시설의 위치를 기존 만 입구부, 마창대교 인근, 그리고 돝섬 인근으로 가정하였으며, 선박운항 횟수와 연간조위를 분석하여 통항빈도가 가장 낮은 새벽시간(01∼05) 및 수두차가 가장 큰 대조기에 운용된다고 가정하였다. 또한, 재해방지시설과 함께 약 10km 길이의 유출ㆍ입 관로를 통한 내ㆍ외해수의 해수교환 촉진을 위한 추가 실험안을 구성하였다. 수치모의 결과, 현재상태의 경우 마산만 전체 해수교환율은 38.62%을 나타냈으며, 모든 실험안에서 마산만 내 모든 구역에서 꾸준한 증가 추세를 보이고 있다. 이에 반해, 마산만 입구부와 비교한 마산만 내측의 해수교환율은 매우 낮게 나타나 반폐쇄성 내만해역의 특성을 잘 재현하는 것으로 판단된다. 재해방지시설과 관로를 이용한 실험안을 분석한 결과, 현재상태와 비교하여 재해방지시설을 운용한 경우 해수교환율이 높고, 그 운용빈도가 많아질수록 더 많은 순환이 이루어지는 것으로 나타났다. 또한, 재해방지시설에 의해 발생된 수두차를 이용하여 관로를 통해 해수를 유입 혹은 유출한 경우 마산만 가장 내측의 수질이 개선되는 것으로 나타났다. 재해방지시설의 위치는 마창대교 남측과 비교하여 마산만 입구와 돝섬에 위치한 경우 해수교환 효과가 더 좋게 나타났다. 한편 마산만 전체영역에 대한 해수교환율은 만 입구에 재해방지시설이 위치한 경우가 돝섬에 위치한 경우보다 높지만, 마산만 내측을 포함한 해수교환율은 반대로 돝섬에 위치한 경우가 더 높게 나타났다. Masan bay with a semi-enclosed waters has serious water quality problems due to the low flow and river pollution load from land, and shows the vulnerable locational characteristics to storm surge. We are seeking the way of both operating disaster prevention facilities and water quality improvement measures in the bay. That is, the water was exchanged using the head difference occurred by operating disaster prevention facilities. The location of disaster prevention facilities was assumed to be in the inlet of the bay, in the vicinity of Machang bridge, and in the vicinity of Dot island and the operation time was assumed to be early morning hours(01∼05) considering the number of shipping passage and annual tide, and spring tide of the largest head difference. In addition, the experiment case of water exchange including the in-outflow feeder pipe was tested. According to the simulation results, water exchange rate in all experiments has shown a steady increase. Water exchange rate of the whole of Masan bay in the case of present is 38.62%. The water exchange rate of the inside of Masan bay compared with the inlet of bay, appeared to be very low. Thus, we judged that the characteristics of semi-enclosed waters were well reproduced. On the results of the experiment of disaster prevention facilities and in-outflow feeder pipe, the case of the operation of disaster prevention facilities, water exchage rate is high compared with the case of present. And, the higer the operating frequency, the more water exchange is appeared. The cases of water exchange prevention facilities through the in-outflow feeder pipe caused by the head difference, also showed the higest improvement of the water quality. Compared with the south of Machang bridge, the effect of water exchange was better in the inlet of Masan bay and Dot island. On the other hand, the inlet of Masan bay is higer than Dot island as for water exchange of the whole of Masan bay, but opposite, water change rate including Masan inside was higher in the case of Dot island.

구조물 설치에 따른 봉포 해수욕장 연안 표사수지 평가

김권수(Gweon-su Kim),유하상(Ha-sang Ryu),김석천(Seok-cheon Kim),김맹진(Mang-Jin Kim) 한국연안방재학회 2020 한국연안방재학회지 Vol.7 No.4

The coastal areas of South Korea are experiencing changes in erosion and sedimentation due to the irregular movements of silt and sediment in rivers and coasts. Erosion is particularly significant on the east coast due to changes in wave characteristics caused by the construction of artificial structures. Coastal erosion can be mitigated by evaluating coastal sediment budget based on long-term changes in wave characteristics and climate and by establishing a clear coastal management system accordingly. We investigated the changes in the movement of sand by waves, by performing an experiment to estimate the amount of sediment movement for Bongpo Beach that has been categorized as “severe” in the coastal erosion status data of the Ministry of Oceans and Fisheries(Ministry of Oceans and Fisheries, 2019). 54 representative waves were generated with input reduction tools. Each representative wave was used as input data for the Delft3d flow model and the SWAN wave model. And the final sedimentation results were calculated by considering the ratio corresponding to each representative wave. Finally, the four submerged breakwater and the one groin, which are currently installed in front of Bongpo, were simulated to analyze the changes in sedimentation before and after the structure.

장기파랑 자료수를 제어한 퇴적물이동 계산시간 감소 방안

김권수(Gweon-su Kim),유하상(Ha-sang Ryu),김상훈(Sang-hoon Kim) 한국연안방재학회 2021 한국연안방재학회지 Vol.8 No.4

In order to solve the difficulty of performing a numerical model using a long-term wave time series, a method of reducing wave time series was considered. And Numerical simulation of the sediment by the Delft3d model at the Maengbang Beach was conducted to verify the validity of the method. NOAA wave data were collected for about 40 years from January 1979 to May 2019. Among them, waves, which are judged to have insignificant effect on the beach, were removed and the wave time series was reduced. To this end, the entire wave time series was graded at intervals of 0.5m, period 2sec, and wave direction 10° to generate a total of 749 representative waves, and a numerical simulation of sediment was performed for each representative wave for 1 day. When the maximum sediment height was less than 0.01m/day, it was assumed that the influence of the representative wave on the area was negligible. As a result of conducting numerical simulation of the sediment using the 23-month real-time waves and the wave by the reduced time series, the difference between the two simulation results indicates a local sedimentation difference of 0.1 to 0.5 m near Deokbongsan. There is a difference in sedimentation of 0.01 to 0.1m overall, and the pattern of repeated erosion and sedimentation along the entire coast is very similar to both real-time waves and reduced time series waves.

SPH를 이용한 쇄파역에서의 비선형 천수거동에 관한 연구

조용준 ( Yong Jun Cho ),김권수 ( Gweon Su Kim ) 서울시립대학교 산업기술연구소 2006 산업기술연구소논문집 Vol.14 No.-

Nonlinear shoaling characteristics over surf zone were numerically investigated based on spatially averaged Navier-Stokes equation. We also test the validity of gradient model for turbulent stresses due to wave breaking using the data acquainted during SUPERTANK LABORATORY DATACOLLECTION PROJECT (Krauss et al., 1992). It turns out that the characteristics length scale of breaking induced current is not negligible, which firmly stands against ever popular gradient modelk-ε model - , but favors Large Eddy Simulation with finer grid deployed. Based on these observations, we modeled the residual stress of spatially averaged Navier-Stokes equation after Smagorinsky. We numerically integrated newly proposed wave equations using SPH with Gaussian kernel function. Severely deformed water surface profile, free falling water particle, queuing splash after landing of water particle and wave finger due to structured vortex on rear side of wave crest (Narayanaswamy and Dalrymple, 2002) were successfully duplicated in the numerical simulation of wave propagation over

제체의 갑작스런 붕괴로 인한 충격파 수치해석 : SPH(Smoothed Particle Hydrodynamics)를 중심으로

조용준(Cho Yong Jun),김권수(Kim Gweon Su) 대한토목학회 2008 대한토목학회논문집 B Vol.28 No.3B

최근 진행된 정밀 수치해석 기법의 비약적인 발전에도 불구하고 SPH 등과 같은 고급수치기법의 수자원 분야에서의 활용은 그리 활발해 보이지 않는다. 대규모 수계를 대상으로 한 flood routing의 경우 비선형 천수방정식으로 대표되는 depth averaged approach가 효과적이나 정밀한 범람고 예단에는 오류가 야기될 수 있다. 본 고에서는 SPH 수치해석 기법의 수자원 분야로의 적용가능성을 모색하기 위해 비교적 수리모형실험자료가 풍부한 제체붕괴로 인한 수리현상을 수치모의하였다. (Martin과 Moyce, 1952). 보다 완벽한 검증을 위해 수로에 장애물이 거치된 경우 (Koshizuka 등, 1995), 수문의 갑작스런 개방으로 인한 수로에서의 수리현상 (Janosi 등, 2004) 등 점진적으로 난이도를 높여 수치모의를 수행하였다. 동수역학 모형 방정식으로는 Navier-Stokes 방정식, 동수역학의 수치적 적분에는 Smoothed Particle Hydrodynamics 기법을 채택하였다. 모의 결과 본 고에서의 수치모의가 기존에 선호되던 VOF, MAC의 수치 기법에 비해 우월한 결과를 보였다. Even though there is a great deal of progress in a numerical method of high caliber like SPH, it is very rarely deployed in a water resources community. Despite the great stride in computing environment, depth averaged approach like a nonlinear shallow equation is still efficient tool for flood routing in large watershed, but it can give some misleading information like the inundation height of flood. In this rationale, we numerically simulate the flow into the dry channel, dry channel with an obstacle triggered by the collapse of a two dimensional water column using SPH (Smoothed Particle Hydrodynamics) in order to boost the application of numerical method of high caliber like SPH in a water resources community. As a most severe test of the robustness of SPH, we also carry out the simulation of the flow through a clearance into the wet channel driven by the rapid removal of a water gate. As a hydrodynamic model, we used the Navier-Stokes equation, a numerical integration of which was carried out using SPH. To verify the validity of newly proposed numerical model, we compare the numerically simulated flow with the others in the literature mainly from VOF and MAC, and hydraulic experiments by Martin and Moyce (1952), Koshi-zuka et al. (1995) and Janosi et al. (2004). It was shown that agreements between the numerical results in this study and hydraulic experiments are remarkable.