Earticle

하도홍수추적을 위한 수문학적 방법인 머스킹검 방법은 유입량, 유출량 그리고 저류량의 관계를 활용하여 유출량을 예측하는 방법이다. 머스킹검 방법에 관한 많은 연구가 진행되면서 필요한 매개변수들은 점점 늘어나게 되었고, 많은 매개변수로 인해 계산과정이 복잡해졌다. 이러한 문제를 해결하기 위해 최적화 알고리즘을 머스킹검 방법의 매개변수 산정에 적용하였다. 본 연구는 Advanced Nonlinear Muskingum Model considering continuous flow (ANLMM-L)를 Wilson 홍수자료와 Sutculer 홍수자료에 적용하여 Linear Munsingum Model incorporating Lateral flow (LMM-L)과 Kinematic Wave Model (KWM)의 결과와 비교하였다. 관측 유출량과 모의 유출량과의 비교를 위한 지표로 Sum of Squares (SSQ)를 사용하였다. Exponential Bandwidth Harmony Search with Centralized Global Search (EBHS-CGS)가 ANLMM-L의 매개변수 산정에 적용되었다. Wilson 홍수자료에 적용한 결과 LMM-L보다 ANLMM-L이 정확한 결과를 나타냈다. Sutculer 홍수자료에서는 ANLMM-L이 KWM보다 좋은 결과를 보이긴 했으나, Sutculer 홍수자료의 유량이 크기 때문에 Wilson 홍수자료의 경우에 비해 SSQ가 크게 나타났다. EBHS-CGS는 본 연구에서 적용한 머스킹검 홍수추적뿐만 아니라 다양한 수자원 공학 문제에 적용할 수 있을 것이다.

Muskingum, a hydrologic channel flood routing, is a method of predicting outflow by using the relationship between inflow, outflow, and storage. As many studies for Muskingum model were suggested, parameters were gradually increased and the calculation process was complicated by many parameters. To solve this problem, an optimization algorithm was applied to the parameter estimation of Muskingum model. This study applied the Advanced Nonlinear Muskingum Model considering continuous flow (ANLMM-L) to Wilson flood data and Sutculer flood data and compared results of the Linear Nonsingum Model incorporating Lateral flow (LMM-L), and Kinematic Wave Model (KWM). The Sum of Squares (SSQ) was used as an index for comparing simulated and observed results. Exponential Bandwidth Harmony Search with Centralized Global Search (EBHS-CGS) was applied to the parameter estimation of ANLMM-L. In Wilson flood data, ANLMM-L showed more accurate results than LMM-L. In the Sutculer flood data, ANLMM-L showed better results than KWM, but SSQ was larger than in the case of Wilson flood data because the flow rate of Sutculer flood data is large. EBHS-CGS could be appplied to be appplicable to various water resources engineering problems as well as Muskingum flood routing in this study.

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. The relation between the load applied to the shaft or sleeve and the relative displacement of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important fur dynamic numerical simulations. A boundary value problem fur the bushing response leads to the load-displacement relation, which requires complex calculations. Therefore, by modifying the constitutive equation for a nonlinear viscoelastic incompressible material developed by Lianis, the data for the elastomeric bushing material was obtained and this data was used to derive the new load-displacement relation for radial response of the bushing. After the load relaxation function for the bushing was obtained from the step displacement control test, Pipkin-Rogers model was developed. Solutions were allowed for comparison between the results of the modified Lianis model and those of the proposed model. It was shown that the proposed Pipkin-Rogers model was in very good agreement with the modified Lianis model.

A newly developed heuristic algorithm, Harmony Search, is applied to the parameter calibration problem of the nonlinear Muskingum model. The Harmony Search could, mimicking the improvisation of music player, find better parameter values for in the nonlinear Muskingum model than five other methods including another heuristic method, genetic algorithm, in the aspect of SSQ(the sum of the square of the deviations between the observed and routed outflows) as well as in the aspects of SAD(the sum of the absolute value of the deviations), DPO(deviations of peak of routed and actual flows) and DPOT(deviatios of peak time of routed and actual outflow). Harmony Search also has the advantage that it does not require the process of asuming the initial values of desing parameters. The sensitivity analysis of Harmony Memory Considering Rate showed that relatively large values of Harmony Memory Considering Rate makes the Harmony Search converge to a better solution.

This paper propose a new short-term interest rate model having a different nonlinear drift function and the same diffusion coefficient with Chan, Karolyi, Longstaff, and Sanders (1992) model. The fractional polynomial power of the drift function in our model is linked to the local volatility elasticity of the diffusion coefficient. While the nonlinear drift function estimated by A¨ıt-Sahalia (1996a) and others has a feature that higher interest rates tend to revert downward and low rates upward, the drift function estimated by our nonlinear model shows that higher interest rate mean-reverts strongly, but, medium rates has almost zero drift and low rates has a very small drift. This characteristic coincides the empirical result based on the nonparametric methodology by Stanton (1997) and the implication by the scatter plot of the short rate data. Furthermore, if our model is transformed to make the diffusion process have a constant term, the drift term in our model is very similar to that in A¨ıt-Sahalia model. In the viewpoint of data, while his model is applied to the original interest rate data, our model is applied to the transformed data.

주요한 에너지원 중의 하나인 천연가스는 비전통 가스의 개발 및 후쿠시마 원전 사고로 인하여 앞으로 더욱 그 중요성이 커질 것으로 전망된다. 이러한 시점에서 앞으로의 천연가스 수요 전망에 활용하기 위하여, 본 연구에서는 비선형 모형 중 하나인 Weibull 모형을 이용하여 경제 성장에 따른 천연가스의 소비 형태를 분석하였다. 분석 대상으로는 OECD 7대 에너지 소비국을 선정하였으며 경제 성장에 따른 에너지 소비의 형태가 S형 곡선의 형태로 나타날 수 있다는 가설을 바탕으로 천연가스에 대해서도 가설이 성립되는지 분석해 보았다. 분석 결과, 1차 에너지 소비와 마찬가지로 천연가스 소비에 대해서도 Weibull 모형을 통한 모형화의 설명력이 매우 높은 것으로 나타났다. 그러나 국가 별 차이도 존재하는 것으로 분석되어 각 국가의 에너지 믹스를 중심으로 분석 결과에 대한 함의를 도출해 보았다.

Due to the development of unconventional gas and the Fukushima nuclear disaster, the importance of natural gas as a primary energy source is higher than before. Through nonlinear Weibull model, we analyzed the natural gas consumption to prepare the demand changes in the future. With the data from seven countries of OECD members, the energy-growth hypothesis (the relationship between energy consumption and economic growth can be represented by a S-shaped curve) for natural gas is tested. As results, natural gas consumption as well as total primary energy supply was well explained via S-shaped (Weibull) curve. However, the shape difference between countries was also existed. We thus drew the implications from the results based on the energy mix of each country.

PURPOSES : This paper presents a comparison study between dynamic and static analyses of falling weight deflectometer (FWD) testing, which is a test used for evaluating layered material stiffness. METHODS: In this study, a forward model, based on nonlinear subgrade models, was developed via finite element analysis using ABAQUS. The subgrade material coefficients from granular and fine-grained soils were used to represent strong and weak subgrade stiffnesses, respectively. Furthermore, the nonlinearity in the analysis of multi-load FWD deflection measured from intact PCC slab was investigated using the deflection data obtained in this study. This pavement has a 14-inch-thick PCC slab over fine-grained soil. RESULTS: From case studies related to the nonlinearity of FWD analysis measured from intact PCC slab, a nonlinear subgrade model-based comparison study between the static and dynamic analyses of nondestructive FWD tests was shown to be effectively performed; this was achieved by investigating the primary difference in pavement responses between the static and dynamic analyses as based on the nonlinearity of soil model as well as the multi-load FWD deflection. CONCLUSIONS : In conclusion, a comparison between dynamic and static FEM analyses was conducted, as based on the FEM analysis performed on various pavement structures, in order to investigate the significance of the differences in pavement responses between the static and dynamic analyses.

The purpose of this paper is to develop a more precise damper model of the joint for the quantification of the joint mechanical properties. We modified the linear damper model of a knee joint model to nonlinear one. The normalized RMS errors between the simulated and measured joint angle trajectories during passive pendulum test became smaller with the nonlinear damper model than those of the linear one which indicates the nonlinear damper model is better in precision and accuracy. The error between the experimental and simulated knee joint moment also reduced with the nonlinear damper model. The reduction in both the trajectory error and the moment error was significant at the latter part of the pendulum test where the joint angular velocity was small. The nonlinearity of the damper was significantly greater at thin subject group and this indicates the nonlinearity is a useful index of joint mechanical properties.

본(本) 논문(論文)에서는 콘크리트의 점진적(漸進的) 인장파괴현상(引張破壞現象)을 해석(解析)할 수 있는 증분형(增分形)이며, 진로종속적(進路從屬的)이고, 텐서적으로 불변성(不變性)인 비선형구성(非線型構成)모델이 제안(提案)되었다. 전(全) 변형도(變形度)는 탄성성분(彈性成分)과 비탄성성분(非彈性成分)의 합(合)으로 표시(表示)된다. 콘크리트내부(內部)에는 미세균열(微細龜裂)의 근원(根源)이 되는 약(弱)한 면(面)들이 모든 방향(方向)으로 좌우(左右)하며, 이 약(弱)한 면(面)에서의 법선응력(法線應力)은 법선변형도(法線變形度)의 함수라고 가정된다. 이와 같은 근본개념(根本槪念)아래 가상(假想)일의 원리(原理)로부터 콘크리트의 접선강도(接線剛度)가 유도된다. 본(本) 이론(理論)은 비비례하중(非比例荷重)이나 주응력(主應力)의 방향(方向)이 변(變)하는 경우 등의 일반적(一般的)인 하중상태(荷重狀態)에 적용할 수 있으며, 이것이 본(本) 모델의 주요(主要)한 목적이 될 수 있다. 본(本) 이론(理論)을 변형연화현상(變形軟化現象)을 보이는 직접인장실험자료(直接引張實驗資料)와 비교한 결과 좋은 일치를 얻었다.

Presented is a nonlinear constitutive model for progressive tensile fracturing of concrete. The model is incremental, path-dependent, and tensorialy invariant. The total strain tensor is assumed to be a sum of a purely elastic component and an inelastic component. The material is considered to contain weak planes of all directions which characterize the planes of the microcracks. A one-to-one functional dependence is assumed between the normal stress and the normal strain across each of the weak planes. The tangential stiffness of concrete is then derived form the principle of virtual work. The present theory can be applied to loading histories which are nonproportional or during which the principal directions rotate. Good agreement with the available direct tensile test data which cover strain-softening is demonstrated.

PURPOSES : The nonlinear model of fatigue cracking is typically used for determining the maintenance period. However, this requires that the model parameters be known. In this study, the particle filter (PF) method was used to determine various statistical parameters such as the mean and standard deviation values for the nonlinear model of fatigue cracking. METHODS : The PF method was used to determine various statistical parameters for the nonlinear model of fatigue cracking, such as the mean and standard deviation. RESULTS : On comparing the values obtained using the PF method and the least square (LS) method, it was found that PF method was suitable for determining the statistical parameters to be used in the nonlinear model of fatigue cracking. CONCLUSIONS : The values obtained using the PF method were as accurate as those obtained using the LS method. Furthermore, reliability design can be applied because the statistical parameters of mean and standard deviation can be obtained through the PF method.

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the load applied to the shaft or sleeve and the relative deformation of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important for dynamic numerical simulations. A boundary value problem for the bushing response leads to the load-displacement relation which requires complex calculations. Therefore, by modifying the constitutive equation fur a nonlinear viscoelastic incompressible material developed by Lianis, the data fur the elastomeric bushing material was obtained and this data was used to derive the new load-displacement relation for radial response of the bushing. After the load relaxation function for the bushing is obtained from the step displacement control test, Pipkin-Rogers model was developed, Solutions were allowed fur comparison between the results of Modified Lianis model and those of the proposed model. It is shown that the proposed Pipkin-Rogers model is in very good agreement with Modified Lianis model.

An elastomeric bushing is a device used in automotive suspension systems to cushion the force transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid metal shaft at its inner surface and a metal sleeve at its outer surface. For axial motion case, the relation between the force applied to the shaft and their relative displacement was considered. In this paper, the relation between the moment applied to the shaft and their relative deformation(angle of rotation) is considered for the torsional motion case. Numerical solutions of the boundary value problem represent the exact bushing response for use in the method for determining the moment relaxation function of the bushing. Solutions also allow for comparison between the exact moment-deformation behavior and that predicted the proposed model. It is shown that the predictions of the proposed moment-deformation relation are in very good agreement with the exact results.

균열 암반 매질에서의 지하수 흐름과 오염물질 이송에 대한 수치모의 실험이 hydromechanic 모형과 추계적 그리고 이산적 3차원 균열망 모형에 바탕을 둔 비정상상태 흐름 수치 모형을 이용하여 수행되었다. 오염물질 이송에 대한 수치모의 실험에서 random walk의 일종인 particle following 알고리즘이 사용되었다. 이 연구의 목적은 지하 깊은 곳에 위치한 Hot dry rock에서의 지열 개발을 위해 프랑스 Soultz sous Foret 지역에 설치된 두개의 깊은 착정인 GPK1과 GPK2 사이에서의 tracer test 반응을 1995년에 실행된 유체순환 현장 실험으로 부터 얻어진 자료를 이용하여 예측하는 것이다. 모의 실험 결과 비반응입자(nonreactive particles)에 대한 평균 이송시간은 두 착정 사이에서 약 5일이었다.

Numerical simulations for fluid flow and solute transport in a fracture rock masses are performed by using a transient flow model, which is based on the three-dimensional stochastic and discrete fracture network model (DFN model) and is coupled hydraulic model with mechanical model. In the numerical simulations of the solute transport, we used to the particle following algorithm which is similar to an advective biased random walk. The purpose of this study is to predict the response of the tracer test between two deep bore holes (GPK1 and GPK2) implanted at Soultz sous Foret in France, in the context of the geothermal researches.l The data sets used are obtained from in situcirculating experiments during 1995. As the result of the transport simulation, the mean transit time for the non reactive particles is about 5 days between two bore holes.

The TIDE, nonlinear finite element model for the simulation of tidal analysis in a shal- low ooastal area was tested for its applicability at the Saemankeum day. Calibration of the TIDE model has been carried out using the six observed field data collected at five locations within the region for tidal velocity. Verification tests have been done using the six observed field data and four data o- tained from the hydraulic model test for the tidal velocity and elevation. Since the simula- tion results for the tidal elevation at Kunsan outer port by the TIDE model are well agreed with the results from the tidal table for one month, it is proved that the TIDE model may be used effectively to predict the tidal movement in the Saemankeum bay for a longer period.

사하중과 단조 활하중을 받고 있는 철근콘크리트판에 대한 일반적인 유한요소 해석방법을 개발하였다. 이 방법을 통하여 탄성, 비탄성 및 극한범위에서 하중-변형 응답과 균열전파를 추적할 수 있었고 또한 응답 경로를 통하여 콘크리트와 철근의 내부응력을 결정할 수 있었다. 면내응력과 휨응력간의 상호작용을 고려하는 층분할된 8 절점 등매개변수 요소를 개발하였다. 수치해를 구하는 방법은 접선증분 강성도법을 이용하였다. 본 해법에 대한 유효성을 검토하기 위하여 다른 해석결과들과 비교하였다.

A general finite element method is developed to analyze reinforced concrete plates under dead loads and monotonically increasing live loads. This method can be used to trace the load-deformation response and crack propagation through elastic, inelastic and ultimate ranges. The internal concrete and steel stresses can also be determined for any stage of the response history. A layered 8 node isoparametric element taking account of coupling effect between the membrane and the bending action is developed. An incremental tangent stiffness method is used to obtain a numerical solution. Validity of the method is studied by comparing the numerical solutions with other results.

유효강우량(有效降雨量), 섬체시간(暹滯時間) 및 유출(流出)의 비선형(非線型)을 포함하는 비선형(非線型) 수문학적(水文學的) 모형(模型)이 기술(記述)된다. 모형(模型)의 입력자료(入力資料)를 구성하는 유효강우량(有效降雨量)의 산정(算定)은 polynomial fitting 방법(方法)이 이용되었으며 섬체시간(暹滯時間)의 비선형성(非線型性)이 고려된 비선형섬체모형(非線型暹滯模型)을 남한강(南漢江) 상류(上流)에 위치한 섬강유역(蟾江流域)에 적용하여 상수(常數)값을 산정하고 종래의 방법인 fitting 방법(方法) 및 저류함수모형(貯溜凾數模型)에 변형(變型)을 가한 상관모형(相關模型)의 상수(常數)값들과 비교하였다. 각 모형(模型)에서 구한 상수(常數)값의 결과로부터 본연구(本硏究)의 수학적(數學的) 해법(解法)인 연속근사해법(連續近似解法)과 수치해법(數値解法)인 Newton-Rhapson 방법(方法)이 비선형(非線型) 유출과정해석(流出過程解析)에서 종전의 계산도해법(計算圖解法) 등에 비해 우수함이 밝혀졌다.

Nonlinear hydrological model containing the nonlinearity of effective rainfall, lag time and runoff is presented. In the evaluation of rainfall excess, the polynomial fitting method for total rainfall, 5 day antecedant rainfall and direct runoff is developed. In the application to actual watershed, the estimated model parameters of nonlinear lag model reflecting the nonlinearity of lag time are compared with the parameters, by both the fitting method and the correlation, model which are the modified version of the storage function model. The Successive Approximation Method in mathematical solution and Newton-Rhapson method in numerical solution are found to be superior to the conventional numerical graphic method in the analysis of nonlinear processes.

콘크리트 구조물의 실제적인 응력과 변형률의 관계를 알기 위해서는 크리프와 수축에 관한 구성방정식을 정량화하는 것이 필요하다. 본 연구는 콘크리트의 시간의존적인 변형 중에서 크리프 변형에 관한 현상학적인 문제를 수학적으로 전개하고 유변학적 접근방법을 사용하여 크리프에 관한 예측모델을 구성한다. 고전적인 4-매개변수 모델에 기초하여 각각의 변형성분을 조합하고, 적절한 크리프 변형을 얻어내기 위한 4개의 매개변수들을 재령영향과 겔 입자간의 연결을 제거하려는 미세프리스트레스의 영향을 고려하여 비선형 함수로 구성된 매개변수들을 전개하며 회복이 불가능한 점성변형에 대하여 습윤평형상태와 건조상태에서 모두 예측할 수 있는 유효점성계수를 유도한다. 본 연구에서 제안한 예측모델은 실험결과와 상관계수 99%이상의 우수한 결과를 제공하고 있다.

To obtain realistic stress-strain relation in concrete, it is necessary to improve the constitutive model for creep and shrinkage of concrete. This study is made up with predicting model of creep using rheological approach and mathematical development which is solution for phenomenon of concrete creep. Long-term deformation components are combined based on traditional 4-parameters model. Creep deformation is obtained adequately using 4-parameters determined by considering aging effect and microprestress among gels. And coefficient of effective viscosity is able to represent both basic creep and total creep included drying creep. This study attempt to establish mathematical model considering effects of aging, hydration, and variations of pore humidity. It can predict both basic creep and total creep. Values of result between prediction and experiment have greater than correlation factor 99%. Additionally experimental results report bad consentaneity with highway design specification adopting FIB MC 90. Rather than those are similar to FIB MC 90 rev.99.

우리나라 전력시장 발전부문에 경쟁을 도입함으로써 각발전사들이 얼마나 발전해야 할지는 중요한 문제가 되었고, 안정적인 계통한계가격(System Marginal Price, SMP)유지는 중요한 문제다. 본 연구에서는 인공신경망 중 MLP(Multi-Layer Perceptron), NARX(Nonlinear Autoregressive exogenous)를 이용하여 서로 비교 분석했고 외부변수로 전력수요를 설정하여 SMP를 예측했으며, ARIMA(Autoregressive Integrated Moving Average)와도 비교를 실시했다. 모두 30일, 40일, 50일을 예측해 봤으며 MLP의 경우 은닉층의 개수가 90개, 85개, 80개 였을 때 최적의 결과를 보여준 반면, NARX의 경우 95개, 80개, 70개 였을 때 최적의 결과를 보여주었다. 전반적으로 모든 예측에서 ARIMA, MLP, NARX 순으로 예측 오차가 작게 나타났다.

With the introduction of competition in the power generation sector in Korea, determining how much each electricity company should develop and maintain a stable system marginal price (SMP) has become an important issue. In this study, SMP was predicted by comparing the values for each company using a multilayer perceptron (MLP) and nonlinear autoregressive exogenous (NARX) model among artificial neural networks (ANN), and setting electricity demand as an external variable. The Autoregressive Integrated Moving Average (ARIMA) was also compared. Each method predicted 30, 40, and 50 days. In the case of MLP, optimal results were obtained when the number of hidden layer units were 90, 85, and 80, whereas in the case of NARX, optimal results were obtained when the number of hidden layer units were 95, 80, and 70. Overall, the forecast errors were small in the order of ARIMA, MLP, and NARX for all predictions.

본 연구는 네 차례에 걸친 종단 조사를 통해, 졸업 후 8개월까지 취업을 하지 못한 대졸 미취업자들의 정신건강 변화와 이 변화에서의 진로 정체감 효과를 비선형 다층모형을 통해 살펴보았다. 그 결과, 대졸 미취업자들의 정신건강의 변화양상은 4학년 1학년 시점을 시작으로 시간에 흐름에 따라 통계적으로 유의미하게 변화하였고, 정신건강 변화에 영향을 미치는 진로미결정과 직업에 대한 지각된 통제감(이후 지각된 통제감)은의 졸업 이전 정신건강 수준에서 차이가 있는 것으로 나타났다. 구체적으로 살펴보면, 대졸 미취업자들의 정신건강은 4학년 1학기를 시작으로 졸업 시점 즈음까지 GHQ 수치가 계속 높아지다가 졸업 이후 1~2개월인 3월과 4월 즈음에 가장 정점을 이루며 가장 좋지 않은 정신건강 상태를 나타냈다. 하지만 그 시점 이후에는 실업의 장기화와 함께 GHQ 수치가 다시 낮아지면서 정신건강 상태가 좋아지는 양상을 보였다. 정신건강 변화에서의 진로 정체감 효과의 경우, 진로미결정 수준이 낮고 지각된 통제력 수준이 높은 개인들은 초기의 GHQ 총점을 비롯한 GHQ 우울 · 불안 및 GHQ 부적응 수치가 낮았으며 장기 미취업 상태가 되어도 GHQ 수치가 높아지지 않고 계속 낮은 상태로 유지되었다. 반면 진로미결정 수준이 높고, 지각된 통제감 수준이 낮은 개인들은 그렇지 않은 개인들에 비해 실업의 장기화와 더불어 GHQ 수치가 높게 지속되었다. 이 결과는 실업이 개인들에게 동일한 정도로 정신건강에 영향을 주어 정신건강의 패턴은 시간에 흐름에 따라 유사하지만 장기 미취업으로 인한 개개인의 정신건강 수준은 초기의 진로미결정과 지각된 통제감 수준에 의해 달라짐을 보여주었다.

This longitudinal study investigated the change of mental health and career identity effect among unemployed university graduates applied with nonlinear multi-level model. The first purpose of this study was to investigate the change pattern of GHQ(General Health Questionnaire) and GHQ two subscales -GHQ depression, and GHQ disadjustment- with HLM analysis. The results showed that GHQ score (including two subscales) of unemployed significantly increased from T1, T2 and graduation time and it was the highest 1~2 month later after graduation. It meant that unemployed university graduates had the worst mental health after graduation. From this point, GHQ score began to decrease smoothly until 5 month after graduation. GHQ and GHQ depression significantly changed over the time, but GHQ disadjustment didn't. The second purpose of this study was to examine career identity effect(consisting of career indecision and perceive control) on GHQ change. The unemployed who had higher level of career indecision and lower level of perceived control had higher level of GHQ at the initial stage(T1). In addition, they had constantly maintained the higher level of GHQ over the time. On the other hand, the unemployed who had lower level of career indecision and higher level of perceived control held low-leveled GHQ. The implications and limitations of this study were discussed and future directions of study were suggested.

본 연구에서는 부분 식생된 개수로에서 평균흐름 및 난류구조에 관한 수치모의 결과를 제시하였다. 이를 위하여 식생항력항이 포함된 레이놀즈 평균 Navier-Stokes 방정식을 수치해석 하였고 난류 모형으로 비선형 k-${\varepsilon}$ 모형을 이용하였다. 제시된 모형을 Nezu and Onitsuka (2001)의 실험수로에 적용하여 모의된 결과를 실험 계측자료 및 Kang and Choi (2006)의 Reynolds stress model 모의결과와 비교하였다. 실험결과와 비교한 결과에 따르면, 비선형 k-${\varepsilon}$ 모형이 평균흐름의 대체적인 경향을 잘 모의하는 것으로 확인되었다. 또한, 식생 영역과 비식생 영역의 경계면에서 쌍와 (twin vortices)가 생성되고 난류강도와 레이놀즈 응력의 최대점이 위치하는 것을 확인하였다. 레이놀즈 응력에 대해서는 경향은 잘 모의하지만 정량적으로 과소 산정하는 것으로 나타났다.

This study presents a numerical modeling of mean flow and turbulence structures of partly-vegetated open-channel flows. For this, Reynolds-averaged Navier-Stokes equations with vegetation drag terms are solved numerically using the non-linear k-${\varepsilon}$ model. The numerical model is applied to laboratory experiments of Nezu and Onitsuka (2001), and simulated results are compared with data from measurement and computations by Kang and Choi's (2006) Reynolds stress model. The simulation results indicate that the proposed numerical model simulates the mean flow well. Twin vortices are found to be generated at the interface between vegetated and non-vegetated zones, where turbulence intensity and Reynolds stress show their maximums. The model simulates the pattern of the Reynolds stress well but under-predicts the intensity of Reynolds stress slightly.