• Journal of Ocean Engineering and Technology
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• v.19 no.4 s.65
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• pp.49-55
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• 2005

We constructed and demonstrated a numerical CADMAS-SURF(V4.0) model that reproduces the wave run-up characteristics on the slope of coastal structures and applied it to a permeable coastal structure. We also compared the numerical model with published experimental results on the hydrodynamic phenomena of structures and some numerical results for a modified Pbreak model. In conclusion, the CADMAS-SURF model efficiently simulated wave run-up on the slope of a permeable coastal structure. The inflow/outflow effects from the porous structure boundary were approximately $15\%$ more than with the modified Pbreak model. Nevertheless, the descriptions of the internal hydraulic characteristics still could not be full!! exacted from the result(Fig. 1 참조)s obtained in our model experiment.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.77-81
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• 2007

In this paper, helicopter aerodynamics is simulated in hovering and forwarding flighst. The governing equation is the unsteady Euler equation. To consider the blade motion and moving effects, an overset grid technique is applied in this simulation. At the boundary, the Riemann invariants condition is used for inflow and outflow. To validate this method, the result is compared with Caradonna-Tung's experimental data.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.549-560
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• 2010

Recently, heavy rainfalls due to the climate change in Korea have caused inundation problems in urban sewer networks. In july 2006, a flooding accident at Misari motorboat racing stadium near the Han river occurred due to the effect of record-breaking outflow discharge from Paldang-dam. The purpose of this study was to simulate and analyze the flooding accident at Misari stadium by MOUSE model. The results of simulation analysis indicated that the total flood volume was $1,313,450m^3$. The effect of back water was 85.9% of the total volume which was caused by the manhole accident, and the effect of accumulated runoff was 14.1% of total volume which was caused by non-return valve shutdown. The simulation results of this MOUSE modeling that was linked to the boundary condition of the dynamic flows in the river by DWOPER model showed the potential of successful inundation analysis for sewer networks.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.158-159
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• 2021

When the porous concrete is exposed to the external environment, the internal relative humidity changes from time to time due to the inflow and outflow of moisture. This change in moisture is affected by temperature. The temperature and humidity of concrete is dominant in the carbonation rate, the largest cause of deterioration of concrete. In this study, actual weather data were used as boundary conditions. A carbonization model of concrete temperature and humidity and calcium hydroxide was constructed to perform long-term analysis. There is a slight error in the carbonation formula of the Japanese Academy of Architecture applying the Kishtani coefficient, a representative experimental formula related to carbonization, and the analysis result values. However, considering that it behaves very similarly, it is thought that a fairly reliable numerical analysis model has been established. A slight error is believed to be due to the fact that the amount of residual calcium hydroxide in the carbonated site has not yet been clearly identified.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.157-161
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• 2011

Although many researches have been carried out concerning the watershed division in natural areas, it has not been researched for the urban watershed division. If the boundary between two urban areas is indistinct because no natural distinction or no administrative division is between the areas, the boundary between the urban areas that have the different outlets (multi-outlet urban watershed) is determined by only designer of sewer system. The suggested urban watershed division model (UWDM) determines the watershed boundary to reduce simultaneously the peak outflows at the outlets of each watershed. Then, the UWDM determines the sewer network to reduce the peak outflow at outlet by determining the pipe connecting directions between the manholes that have the multi-possible pipe connecting directions. In the UWDM, because the modification of the sewer network changes the superposition effect of the runoff hydrographs in sewer pipes, the optimal sewer layout can reduce the peak outflow at outlet, as much as the superposition effects of the hydrographs are reduced. Therefore, the UWDM can optimize the watershed distinction in multi-outlet urban watershed by determining the connecting directions of the boundary-manholes using the genetic algorithm. The suggested model was applied to a multi-outlet urban watershed of 50.3ha, Seoul, Korea, and the watershed division of this model, the peak outflows at two outlets were decreased by approximately 15% for the design rainfall.

• Wind and Structures
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• v.31 no.2
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• pp.85-102
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• 2020

Accurate load evaluation is essential in any performance-based design. Design wind speeds and associated wind loads are well defined for synoptic boundary layer winds but not for thunderstorms. The method presented in the current study represents a new approach to obtain design wind speeds associated with thunderstorms and their gust fronts using historical data and Monte Carlo simulations. The method consists of the following steps (i) developing a numerical model for thunderstorm downdrafts (i.e. downbursts) to account for storm translation and outflow dissipation, (ii) utilizing the model to characterize previous events and (iii) extrapolating the limited wind speed data to cover life-span of structures. The numerical model relies on a previously generated CFD wind field, which is validated using six documented thunderstorm events. The model suggests that 10 parameters are required to describe the characteristics of an event. The model is then utilized to analyze wind records obtained at Lubbock Preston Smith International Airport (KLBB) meteorological station to identify the thunderstorm parameters for this location, obtain their probability distributions, and utilized in the Monte Carlo simulation of thunderstorm gust front events for many thousands of years for the purpose of estimating design wind speeds. The analysis suggests a potential underestimation of design wind speeds when neglecting thunderstorm gust fronts, which is common practice in analyzing historical wind records. When compared to the design wind speed for a 700-year MRI in ASCE 7-10 and ASCE 7-16, the estimated wind speeds from the simulation were 10% and 11.5% higher, respectively.

• Journal of the Korean Society of Visualization
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• v.21 no.1
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• pp.80-93
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• 2023

We performed numerical simulations of blood flow in an arterial cerebral artery aneurysm to investigate the hemodynamic behavior after coil embolization. A patient-specific model was created based on CTA data. We also conducted the coil embolization simulation to obtain the coil placement within the aneurysm. Blood was assumed to be an incompressible Newtonian fluid, and both the vessel and coil were considered rigid walls. The pulsatile boundary condition was applied at the inlet, and the outflow boundary conditions were used at the outlets. Our findings demonstrated that the coil embolization significantly reduces the blood volume flowrate entering the aneurysm by effectively blocking the inflow jet, leading to a decrease in both TAWSS and WSS, especially at the systolic peak in the impingement zone. While several high OSI regions disappeared over the aneurysm surface, we observed high OSI regions with a relatively small area where the coil did not completely occlude the aneurysm. Overall, these results quantitatively analyzed the effectiveness of coil embolization by focusing on hemodynamic indicators, potentially preventing aneurysm rupture. The present work could contribute to the development of patient-specific coil embolization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.778-781
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• 2002

Durability of rubber dust cover in the ball joint for automotive suspension parts were analyzed by FEM and compared with experimental data. Upper open area of ball joint is sealed by dust cover for preventing outflow of the lubricating oil and intrusion of send, dust, water, etc. This rubber cover undergoes repeated loadings such as tension and compression while the car is running. Analysis about rubber material needs to consider every kinds of nonlinearities arise in finite element analysis, which are geometric nonlinearity due to large displacement and small strain, materially nonlinearity and nonlinear boundary condition such as contact. So in the study, the deformation behavior of dust cover was analysed by using the commercial finite element program MARC. This program could solve these kinds of nonlinear analysis accurately. Finite element model of dust cover is considered as 3-dimensional half model based on 2-dimensional axisymmetric model. Material property of rubber was modeled by Ogden model and input data for calculation takes form uniaxial tension test of rubber specimen, The final object of the study is obtaining the design specification of dust covers and the result of analysis should be a useful data to design of rubber

• Journal of Korean Society of Water and Wastewater
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• v.9 no.4
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• pp.73-86
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• 1995

The propriety of the numerical model application was examined on Paldang resevoir and its inflow tributaries located in the center of the Korean peninsula and the long term water quality forecast of the oxygen profile was carried out in this syduy. The input data of the model was the capacity of the reservoir, catchment area, percolation, diffusion rate, vertical mixing rate, dissolution rate from the bottom of the reservoir, outflow of the resevoir, water quality measurement and meteorology data of the drainage basin, and the output result was the annual estimation value of the dissolved oxygen concentration and the biochemical oxygen demand. The modeling method is based on the measured or calculated boundary condition dividing the water area into several blocks from the macorscopic aspect and considering the mass balance in these blocks. As the result of the water quality forecast, it was expected that the water quality in Northern Han River and Paldang reservoir would maintain the recent level, but that the water quality in the Southern Han River and its inflow tributary would worsen below the grade 4 of the life environmental standard from around 2000 owing to the decrease of DO concentration and the increase of BOD concentration.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.3 s.108
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• pp.263-269
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• 2006

The objective of the present work is to develop a time-domain numerical method of broadband noise in a cascade of airfoils. This paper focuses on dipolar broadband noise sources, resulting from the interaction of turbulent inflows with the flat-plate airfoil cascade. The turbulence response of a two-dimensional cascade is studied by solving both of the linearised and the full nonlinear Euler equations employing accurate higher order spatial differencing, time stepping techniques and non-reflecting inflow/outflow boundary condition. The time-domain result using the linearised Euler equations shows good agreement with the analytical solution using the modified LINSUB code. Through the comparison of the nonlinear time-domain result using the full nonlinear Euler equations with the linear, it is found that the acoustic mode amplitude of the nonlinear response is less than that of the linear response due to the energy cascade from low frequency components to the high frequency ones. Considering the merits of the time-domain methods over the typical time-linearised frequency-domain analysis, the current method is expected to be promising tools for analyzing the effects of the airfoil shapes, non-uniform background flow, linear-nonliear regimes on the broadband noise due to turbulence-cascade interaction.