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Wenhong Dai
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing 210098, China

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Journal article
Published: 30 May 2020 in Journal of Marine Science and Engineering
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In a coastal environment, this paper investigated the formation process and the cumulative shape of subaqueous mounds formed by hopper dredged discharges. Hydrological observations and field tests were performed to examine the flow features and ultimately generated morphology characteristics. A high-precision digital elevation model (DEM) was established by multi-beam depth sweeping (MBDS) in the experiment. Particular attention was paid to the formation of the mounds, the three-dimensional shape and the influence factors. The field measurements showed that the mounds were roughly symmetrical in space, and the tidal current, though of weak strength, played a certain role in shaping the profiles. Cone and volcanic cone mound tops were observed, featuring the main top shapes. The height and covered area of the mounds were proportional to the amount of dumped sediment, and they were also affected a lot by the water depth. The results of superimposed tests showed that the second placement over the existing mound resulted in a similar overall shape, but there was pronounced movement around the mound; additional discharged volumes at the same location mainly increased the mound height. The field tests provided a reference for understanding the sediment dumping in other similar coastal areas.

ACS Style

Wenhong Dai; Wei Ding; Chuanteng Lu; Xiaofeng Luo; Qiancheng Xie. Field Investigations of Underwater Mounds Formed by Hopper Dredge Discharges in a Coastal Environment. Journal of Marine Science and Engineering 2020, 8, 1 .

AMA Style

Wenhong Dai, Wei Ding, Chuanteng Lu, Xiaofeng Luo, Qiancheng Xie. Field Investigations of Underwater Mounds Formed by Hopper Dredge Discharges in a Coastal Environment. Journal of Marine Science and Engineering. 2020; 8 (6):1.

Chicago/Turabian Style

Wenhong Dai; Wei Ding; Chuanteng Lu; Xiaofeng Luo; Qiancheng Xie. 2020. "Field Investigations of Underwater Mounds Formed by Hopper Dredge Discharges in a Coastal Environment." Journal of Marine Science and Engineering 8, no. 6: 1.

Article
Published: 14 December 2018 in Journal of Hydrodynamics
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The Three Gorges Reservoir (TGR) began operation in 2003 and caused alterations in the natural hydrological regime and severe environmental impacts. Baguazhou Reach, a goose-head pattern of braided channels in lower Yangtze River has emerged due to a series of changes in water and sediment conditions caused by TGR. This paper aims to simulate the hydrodynamic characteristics under the condition of clear water releasing from TGR and analyze the features of deformation within the branches of the reach, also to predict the future effect of hydrodynamic enhancement and additional fluvial processes as well. The results show that the decline of the tributary is mainly controlled by the weakness of inflow energy and contrast in channel resistance. The particular protective measures can effectively enhance hydrodynamic and improve the present situation but, they all result in the deflection of the main water flow and increase the local velocity, and over the long term, deposition also occurred in the junction areas which need special protection.

ACS Style

Wen-Hong Dai; Wei Ding. Hydrodynamic improvement of a goose-head pattern braided reach in lower Yangtze River. Journal of Hydrodynamics 2018, 31, 614 -621.

AMA Style

Wen-Hong Dai, Wei Ding. Hydrodynamic improvement of a goose-head pattern braided reach in lower Yangtze River. Journal of Hydrodynamics. 2018; 31 (3):614-621.

Chicago/Turabian Style

Wen-Hong Dai; Wei Ding. 2018. "Hydrodynamic improvement of a goose-head pattern braided reach in lower Yangtze River." Journal of Hydrodynamics 31, no. 3: 614-621.

Journal article
Published: 11 October 2018 in Water
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A confluence is a natural component in river and channel networks. This study deals, through field and numerical studies, with alluvial behaviors of a confluence affected by both river run-off and strong tides. Field measurements were conducted along the rivers including the confluence. Field data show that the changes in flow velocity and sediment concentration are not always in phase with each other. The concentration shows a general trend of decrease from the river mouth to the confluence. For a given location, the tides affect both the sediment concentration and transport. A two-dimensional hydrodynamic model of suspended load was set up to illustrate the combined effects of run-off and tidal flows. Modeled cases included the flood and ebb tides in a wet season. Typical features examined included tidal flow fields, bed shear stress, and scour evolution in the confluence. The confluence migration pattern of scour is dependent on the interaction between the river currents and tidal flows. The flood tides are attributable to the suspended load deposition in the confluence, while the ebb tides in combination with run-offs lead to erosion. The flood tides play a dominant role in the morphodynamic changes of the confluence.

ACS Style

Qiancheng Xie; James Yang; Staffan Lundström; Wenhong Dai. Understanding Morphodynamic Changes of a Tidal River Confluence through Field Measurements and Numerical Modeling. Water 2018, 10, 1424 .

AMA Style

Qiancheng Xie, James Yang, Staffan Lundström, Wenhong Dai. Understanding Morphodynamic Changes of a Tidal River Confluence through Field Measurements and Numerical Modeling. Water. 2018; 10 (10):1424.

Chicago/Turabian Style

Qiancheng Xie; James Yang; Staffan Lundström; Wenhong Dai. 2018. "Understanding Morphodynamic Changes of a Tidal River Confluence through Field Measurements and Numerical Modeling." Water 10, no. 10: 1424.

Journal article
Published: 24 August 2018 in International Journal of Sediment Research
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Estimation of sedimentation in reservoirs helps in the management and design of the reservoir's useful capacity. This research was done on the Awash River basin at the Koka Dam Reservoir in Ethiopia. The method applied was the loose integration of the Soil and Water Assessment Tool (SWAT) model and Hydrologic Engineering Center-River Analysis System (HEC-RAS) model for the estimation of the sediment load reaching the reservoir. The SWAT model was used for the estimation of erosion at the catchment level, and the HEC-RAS model was applied to estimate the sediment transport in the river channel. The implemented method allows sedimentation in the floodplains and bed shear stress to be considered in the sediment modeling, which cannot be considered in the SWAT model. In addition, the river cross sectional properties and the hydrodynamic processes in the rivers were considered in the modeling process. The data used in this study are a combination of i) observed data collected by government agencies, ii) data available online in data repositories, and iii) data extracted from remote sensing in the Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM). The calibration and validation of the SWAT model was done by using Sequential Uncertainty Fitting (SUIF-2) calibration and validation tools. The HEC-RAS model was calibrated by adjusting the roughness factor. The output from the integrated approaches gives better estimates of flow and sediment near the inlet to the reservoir, with coefficients of determination of 0.85 and 0.67, respectively, and Nash Sutcliffe coefficients of model fit efficiency of 0.90 and 0.62, respectively, for daily simulations.

ACS Style

Abebe Tadesse; Wenhong Dai. Prediction of sedimentation in reservoirs by combining catchment based model and stream based model with limited data. International Journal of Sediment Research 2018, 34, 27 -37.

AMA Style

Abebe Tadesse, Wenhong Dai. Prediction of sedimentation in reservoirs by combining catchment based model and stream based model with limited data. International Journal of Sediment Research. 2018; 34 (1):27-37.

Chicago/Turabian Style

Abebe Tadesse; Wenhong Dai. 2018. "Prediction of sedimentation in reservoirs by combining catchment based model and stream based model with limited data." International Journal of Sediment Research 34, no. 1: 27-37.

Journal article
Published: 29 June 2018 in Water
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River resistance characteristics, which can be reflected by the resistance factor, have an impact on flow and sediment transport. In the classical theory, Prandtl proposed the mixing length model for the simulation of the turbulence, and von Kármán established the logarithmic formula of the flow velocity distribution. Based on that, the expression of the resistance factor can be derived. With the development of the numerical technology, the k−ε model has been widely applied in the channels computation. However, for the different closure ways of the Reynolds stress in turbulence equations, the outcomes of the k−ε model and the Prandtl mixing length model are not exactly identical. In this paper, both qualitative and quantitative studies are carried out on the difference between these two models, with respect to the resistance factor. This difference is evaluated by the ratio of the resistance factor computed with the two models. The result shows that with the increment of the relative flow depth, the ratio first increases and then decreases. Moreover, it is also affected by the bed slope. Therefore, the difference should be taken into account when a comparison is made between the simulation results of the k−ε model and the classical theory of river mechanics.

ACS Style

Wenhong Dai; Mengjiao Ding; Haitong Zhang. On the Difference of River Resistance Computation between the k − ε Model and the Mixing Length Model. Water 2018, 10, 870 .

AMA Style

Wenhong Dai, Mengjiao Ding, Haitong Zhang. On the Difference of River Resistance Computation between the k − ε Model and the Mixing Length Model. Water. 2018; 10 (7):870.

Chicago/Turabian Style

Wenhong Dai; Mengjiao Ding; Haitong Zhang. 2018. "On the Difference of River Resistance Computation between the k − ε Model and the Mixing Length Model." Water 10, no. 7: 870.

Journal article
Published: 28 May 2018 in Water
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Combined orifice-weir flow is a complex phenomenon in hydropower and the discharge capacity of a structure affects the safety of the structure. It is essential to propose an equation for computing the discharge coefficient of combined orifice-weir flow. Based on theoretical analyses and physical experiments, 284 laboratory tests were performed to determine the discharge coefficient. The parameters affecting the discharge coefficient were determined and the relationships between the coefficient and four parameters, that is, the ratio of the water head to the upstream water level, the ratio of orifice height to orifice-weir height, the ratio of orifice height to the water head, and the ratio of the length to the height of the orifice-weir structure, were established. According to the dimensional analysis and the linear-fitting method of multidimensional ordinary least squares, five models were constructed to analyze the sensitivity of the model’s accuracy by using different parameters. The sensitivity to each parameter was also evaluated. The results were examined with statistical indices and they showed that one model yielded the best results, which were consistent with the experimental values. Thus, the proposed model is effective in estimating the discharge coefficient of combined orifice-weir flow.

ACS Style

Zong-Fu Fu; Zhen Cui; Wen-Hong Dai; Yue-Jun Chen. Discharge Coefficient of Combined Orifice-Weir Flow. Water 2018, 10, 699 .

AMA Style

Zong-Fu Fu, Zhen Cui, Wen-Hong Dai, Yue-Jun Chen. Discharge Coefficient of Combined Orifice-Weir Flow. Water. 2018; 10 (6):699.

Chicago/Turabian Style

Zong-Fu Fu; Zhen Cui; Wen-Hong Dai; Yue-Jun Chen. 2018. "Discharge Coefficient of Combined Orifice-Weir Flow." Water 10, no. 6: 699.

Journal article
Published: 04 March 2018 in Water
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Regime channels are important for stable canal design and to determine river response to environmental changes, e.g., due to the construction of a dam, land use change, and climate shifts. A plethora of methods is available describing the hydraulic geometry of alluvial rivers in the regime. However, comparison of these methods using the same set of data seems lacking. In this study, we evaluate and compare four different extremal hypothesis-based regime methods, namely minimization of Froude number (MFN), maximum entropy and minimum energy dissipation rate (ME and MEDR), maximum flow efficiency (MFE), and Millar’s method, by dividing regime channel data into sand and gravel beds. The results show that for sand bed channels MFN gives a very high accuracy of prediction for regime channel width and depth. For gravel bed channels we find that MFN and ‘ME and MEDR’ give a very high accuracy of prediction for width and depth. Therefore the notion that extremal hypotheses which do not contain bank stability criteria are inappropriate for use is shown false as both MFN and ‘ME and MEDR’ lack bank stability criteria. Also, we find that bank vegetation has significant influence in the prediction of hydraulic geometry by MFN and ‘ME and MEDR’.

ACS Style

Ishwar Joshi; Wenhong Dai; Ahmed Bilal; Akhanda Raj Upreti; Ziming He. Evaluation and Comparison of Extremal Hypothesis-Based Regime Methods. Water 2018, 10, 271 .

AMA Style

Ishwar Joshi, Wenhong Dai, Ahmed Bilal, Akhanda Raj Upreti, Ziming He. Evaluation and Comparison of Extremal Hypothesis-Based Regime Methods. Water. 2018; 10 (3):271.

Chicago/Turabian Style

Ishwar Joshi; Wenhong Dai; Ahmed Bilal; Akhanda Raj Upreti; Ziming He. 2018. "Evaluation and Comparison of Extremal Hypothesis-Based Regime Methods." Water 10, no. 3: 271.

Journal article
Published: 26 January 2018 in Water
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The implementation of floating structures has increased with the construction of new sluices for flood control. The overturning moment of floating structure and its influencing factors are the important parameters that determine the structural safety. It is essential to understand the overturning characteristics of these structures in currents. Based on hydrodynamic theory and equilibrium analysis, the hydraulic characteristics of a floating structure are discussed by means of theoretical analysis and experiments. A formula for the overturning moment is developed in terms of the time-averaged pressure on the structure. The corresponding parametric study aims to assess the effects of flow velocities, vertical positions, shape ratios and water levels on the overturning moment. The experimental results show that hydrodynamic factors have a significant influence on the overturning of the structure. Furthermore, a relationship is obtained between the overturning moment and the contributing parameters according to dimensional analysis and the linear fitting method of multidimensional ordinary least squares (OLS). The results predicted by the formula agree with the experimental results, demonstrating the potential for general applicability.

ACS Style

Zhen Cui; Zong-Fu Fu; Wen-Hong Dai; Zheng-Qing Lai. Submerged Fixed Floating Structure under the Action of Surface Current. Water 2018, 10, 102 .

AMA Style

Zhen Cui, Zong-Fu Fu, Wen-Hong Dai, Zheng-Qing Lai. Submerged Fixed Floating Structure under the Action of Surface Current. Water. 2018; 10 (2):102.

Chicago/Turabian Style

Zhen Cui; Zong-Fu Fu; Wen-Hong Dai; Zheng-Qing Lai. 2018. "Submerged Fixed Floating Structure under the Action of Surface Current." Water 10, no. 2: 102.

Research article
Published: 06 April 2017 in PLOS ONE
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Sediment-dynamics modeling is a useful tool for estimating a dam's lifespan and its cost-benefit analysis. Collecting real data for sediment-dynamics analysis from conventional field survey methods is both tedious and expensive. Therefore, for most rivers, the historical record of data is either missing or not very detailed. Available data and existing tools have much potential and may be used for qualitative prediction of future bathymetric change trend. This study shows that proxy approaches may be used to increase the spatiotemporal resolution of flow data, and hypothesize the river cross-sections and sediment data. Sediment-dynamics analysis of the reach of the Tenryu River upstream of Sakuma Dam in Japan was performed to predict its future bathymetric changes using a 1D numerical model (HEC-RAS). In this case study, only annually-averaged flow data and the river's longitudinal bed profile at 5-year intervals were available. Therefore, the other required data, including river cross-section and geometry and sediment inflow grain sizes, had to be hypothesized or assimilated indirectly. The model yielded a good qualitative agreement, with an R2 (coefficient of determination) of 0.8 for the observed and simulated bed profiles. A predictive simulation demonstrated that the useful life of the dam would end after the year 2035 (±5 years), which is in conformity with initial detailed estimates. The study indicates that a sediment-dynamic analysis can be performed even with a limited amount of data. However, such studies may only assess the qualitative trends of sediment dynamics.

ACS Style

Ahmed Bilal; Wenhong Dai; Magnus Larson; Qaid Naamo Beebo; Qiancheng Xie. Qualitative simulation of bathymetric changes due to reservoir sedimentation: A Japanese case study. PLOS ONE 2017, 12, e0174931 .

AMA Style

Ahmed Bilal, Wenhong Dai, Magnus Larson, Qaid Naamo Beebo, Qiancheng Xie. Qualitative simulation of bathymetric changes due to reservoir sedimentation: A Japanese case study. PLOS ONE. 2017; 12 (4):e0174931.

Chicago/Turabian Style

Ahmed Bilal; Wenhong Dai; Magnus Larson; Qaid Naamo Beebo; Qiancheng Xie. 2017. "Qualitative simulation of bathymetric changes due to reservoir sedimentation: A Japanese case study." PLOS ONE 12, no. 4: e0174931.