• Journal of Industrial Technology
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• v.25 no.A
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• pp.3-14
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• 2005

In order to accurately analyze the detailed hydraulic characteristics of the curved channel in the downstream of dam with the hydraulic structures such as bridge piers, RMA2 model which is one of two-dimensional models is applied to ChunCheon dam downstream curved channel. A series of hydraulic model tests are carried out for comparison studies. HEC-RAS model is also applied to the same site. There are no errors when velocities and water levels resulted from HEC-RAS model RMA2 model are compared with those of hydraulic model test on the straight channel. But, it is found that results of RMA2 model have a better agreement with those of hydraulic model test than those of HEC-RAS model on the curved channel with bridge piers. Additionally, RMA2 model can be predicted the eddy phenomena around bridge piers of the curved channel.

• Journal of Korea Water Resources Association
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• v.37 no.12
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• pp.979-991
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• 2004

In this study, RMA2 and RMA4, the 2-D depth-averaged models, were employed to simulate the two-dimensional mixing characteristics of the pollutants in the natural streams. The velocity and depth were first calculated using RMA2, 2-D hydrodynamic model, and then the resulting flow field was inputted to RMA4, 2-D water quality model, to compute the concentration field. RMA models were verified using the velocity and concentration data measured in S-curved meandering channel. The results showed that the RMA2 model simulated well the phenomenon that the maximum velocity line is located at the Inner bank of meandering channel, and the RMA4 model was well adapted to reproduce the general mixing behavior and the separation of tracer clouds. Comparing model simulations with measured data in the field experiments, RMA2 model simulated well general flow field and tendency that the maximum velocity line skewed toward the outer bank which were found in field experiments. The simulations of RMA4 model showed that the center of the tracer cloud tends to follow the path in which the maximum velocity occurs. In this study, the dispersion coefficients are fine-tuned based on the measured coefficients calculated using field concentration data, and the results show reasonable agreement with predictive equations.

• Journal of Wetlands Research
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• v.15 no.1
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• pp.59-69
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• 2013

The numerical simulations were performed to analyze the advection-diffusion processes of dredging-induced turbidity plume using RMA2 and RMA4 models in Bunam reservoir, Seosan, Chungnam. Field survey was also performed to measure the turbidity using the multi water quality monitoring system (YSI6600EDS). In the field survey, the vertical and horizontal distributions of the turbidity were measured during the dredging operation in Bunam reservoir. RMA2 model was used to simulate the velocity distributions in both the whole domain and the 2nd part of Bunam reservoir. RMA4 model was also used to simulate the concentration distribution in only the 2nd part of Bunam reservoir, where the dredging work were conducted. The comparison of the simulation results with the field data for the advection-diffusion of the turbidity plume using the concentration ratio concepts shows that the numerical model can be applied to analyze the environmental impact of dredging works.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.1
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• pp.101-112
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• 2007

This study has used RMA2 model and RMA4 model, which are depth-averaged two-dimensional flow and water-quality prediction models, to analyze the variation of the water-quality by the gates operation in the Seonakdong River. Sensitivity analysis is performed to get the Manning coefficient and the coefficient of eddy viscosity for RMA2 model, and to get the diffusion coefficient for RMA4 model. Since the numerical simulation using RMA2 and RMA4 models did not consider tributary pollutant load except for that of Joman River, it could make a little difference from the natural phenomenon. Nevertheless, the numerical simulation shows that the discharge of $30m^3/s$, which is the continuous inflow from the Daedong-gate, can make it possible to achieve the target water-quality (BOD 4.3mg/L) of Nakbon-N watershed about 10 days later if the Daejeo-gate could remain opened in connection with the Noksan-gate operation.

• Korean Journal of Environmental Agriculture
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• v.18 no.1
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• pp.18-23
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• 1999

A numerical model of flow velocity in the standing water system is presented. This model(RMA-2), based on the 2-dimensional unsteady momentum and continuity equations, uses finite element techniques to simulate the distribution of velocity over a spatial location of lakes. The present model represents an improvement over existing numerical water quality models in that it can model the unsteady state and can, therefore, cope with time with a spatial location of standing waters such as lakes and large reservoirs. The model thus allows the engineer to do more accurate estimation of water flows and thus water qualities in standing waters where directions and velocities of the flow become more important for the simulation of the water quality than in running waters. Tests for the data collected in the lake "Paldang" indicates that the model works well under limited circumstances. However, to be more accurate estimation of velocity with the present model, accumulation of data for the measurement of velocities and renovation of geometrical conditions of the lake would be needed.

• Journal of Environmental Science International
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• v.17 no.7
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• pp.783-793
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• 2008

The purpose of this study is to analyze the sensitivity of the RMA2 model parameters reflecting the flow characteristics of stream junction and thus understand the hydraulic characteristics of the channel confluence flow. This study dealt with the input parameters of the RMA-2 model, a two-dimensional numerical analysis model widely used for researches both at home and abroad. The parameters of the RMA-2 model are roughness coefficient, turbulent diffusion coefficient, Coriolis forces latitude, Density, and mesh size. This study those parameters estimated from actual heavy rainfall, and varied the parameter size by (-)30%${\sim}$+30% to review the characteristics of the flow characteristics of the channel section. Weobserved that when the ratio of the channel width was relatively small, the smaller the approaching angle was, the farther from the junctions became the generating place of the maximum flow velocity, however, when the ratio of the channel width was relatively large, the larger the approaching angle was, the farther the generating place of the maximum flow velocity from the junctions became. In particular, the distance between junctions and the place where the maximum flow velocity generated showed an absolute correlationover 90% of the relative channel width, but an inverse relationwas found when the distance to the place where the flow velocity generated was shortened as relative the channel width between the main channel and tributary increased.

• Journal of Environmental Science International
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• v.18 no.9
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• pp.971-981
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• 2009

An objective of this study is as follows: 1) performing sensitivity analysis and parameter estimation of RMA2 and RMA4 models for the West-Nakdong River, 2) drawing up alternatives of gates-operation for water-quality enhancement, and 3) quantitative evaluation of methodology of 'flow-restoration by gates-operation' among 'Comprehensive Plan Improving Water-Quality in the West-Nakdong River(WNR)' with the target water-quality(BOD at Nakbon-N point: below 4.3 mg/L). The parameters for the RMA2 (depth-averaged two-dimensional flow model) and RMA4 (depth-averaged two-dimensional water-quality model) were determined by sensitivity analysis. Result of parameter estimation for RMA2 and RMA4 models is $1,000\;Pa{\cdot}s$ of the eddy viscosity, 20 of the Peclet number, 0.025 of the Manning coefficient, and $1.0\;m^2/s$ of the diffusion coefficient. We have evaluated the effects of water-quality enhancement of the selected alternatives by numerical simulation technique with the models under the steady-state flow condition and the time-variant transport condition. Because of no-resuspension from river bottom and considering BOD as conservative matter, these simulation results slightly differ from real phenomena. In the case of $50\;m^3/s$ of Daejeo-gate inflow, two-dimensional flow pn results result represents that small velocity occurs in the Pyungkang Stream and no flow in the Maekdo River. In the WNR, there occurs the most rapid flow near timhae-bridge. In the WNR, changes of water-quality for the four selected simulation cases(6, 10, 30, $50\;m^3/s$ of the Daejeo-gate inflow) were predicted. Since the Daejeo-Gate and the Noksan-Gate can be opened up to 7 days, it would be found that sustainable inflow of $30\;m^3/s$ at the Daejeo-gate makes BOD in the WNR to be under the target of water-quality.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.187-190
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• 2008

The water quality at the Dongbin Harbor at Pohang city, is getting worse due to the sewage and the wastewater from communities. In this syudy, RMA2 and RMA4, which is two-dimensional depth-averaged finite element numerical model, were employed to simulate the improvement of water quality from inflowing water through an inland canal to be planned connecting Dongbin Harbor and the Hyeongsan River. For the comparative result of the numerical model, both the present condition and the restoration condition (after construction of an inland canal) is simulated. The results of these conditions reasonably simulate a real situation at the Dongbin Harbor. After construction of an inland canal, the water quality at the Dongbin Harbor will be compared to the fresh water quality of the Hyeongsan River at the steady state. Futhermore, The result of simulation will be used to decide the most effective dimension of the canal.

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.85-93
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• 1998

This study is to analyze and predict the contaminant transport based on the hydrauli characteristics using 2-dimensional finite element model. The dynamic wate quality model. RMA-4. is used to predict the contaminant transport using the hydrulic characteristics obtained from RMA-2v model. The study region is from downstream of Cham-sil weir to upstream of Shin-Kok weir. From the results of contaminant transport analysis. it is shown that the variations of discharge and velocity give quite large effect to the transport and dispersion of contaminant material. and that the water qualities of Joong-Rang and Tan streams play an important role to the downstream also. when the incidental contaminant accident occurs and contaminant material moves to the downstream. it is resulted the decreasing of the maximum COD and the increasing of the duration time to be affected by contaminant. Finally. 2-dimensional analysis is required in the case of large river like Han River. since the large difference of contaminant concentration has been investigated in the left and right bank.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.349-357
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• 2011

This study has an objective to estimate effect on water-quality enhancement by removal of contaminated river-bed material using a two-dimensional numerical modeling in the Seonakdong River, the Pyunggang River and the Maekdo River. RMA2 and RMA4 models were used for flow and contaminant transport simulation, respectively. After the analysis of the effects of flow restoration plan for the Seonakdong River system made by Lee et al (2008), simulation have been performed about scenarios which contains operations of the Daejeo Gate, the Noksan Gate, the Makdo Gate (on planning), and the Noksan Pumping Station. Because there is no option for elution from bed sediment in the RMA4 model, a simple technique has been used for initial condition modification for elution. The analyses revealed that the effect on water quality improvement due to dredging of bed sediment seemed to be less than 10 % of the total effect. The most efficient measure for the water quality improvement of the river system was the linked operation of water-gates and pumping station.