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| (a) Elevation contour map of velocity near the rectangular pier in the working condition 2, (b) Elevation contour map of velocity near the round pier in the working condition 2 and (c) Elevation contour map of velocity near the oval pier in the working condition 2.
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The shape of bridge piers across rivers is one of the significant factors that affect the backwater in the river. The study on the influence of bridge pier shapes on the flow patterns of the river is valuable to the design of the bridge and river flooding. Based on the MIKE21 Flow Model hydrodynamic model, dynamic numerical simulations were conduct...
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Citations
... Different structure shapes result in different interaction areas and deflection directions, changing the deflection angle, mainstream velocity, and the water exchange rate. Existing studies have shown that pier diameter, shapes and other factors influence the flow field significantly [47,80,81]. The deflection angle that corresponds to the triangular prism and semi-cylinder is approximate and relatively small, generally about 30-45°, while that for the rectangular column is larger, approximately 90° for small l and decreases as l increases. ...
Artificial islands and viewing pavilions can act as barriers in slow-flow water bodies such as lakes and can be used together with water diversion projects to improve the water quality. In this study, based on the particle image velocimetry system, we carried out flume experiments to study the influence of the location and shape of barriers on the purification capacity of a slow-flow water body. We analyzed the velocity composition based on the information entropy H and the vector distributions, average velocity and water exchange rate η. The results reveal that the hydrodynamic characteristics are significantly optimized by barrier structures. η doubles if the barrier structure is reasonably designed, and it is positively correlated with the average velocity. In all cases, the highest η is recorded for a barrier shaped as a rectangular column and increases with the interaction area between the flow and structure. The water purification capacity and flow velocity gradually increase with increasing flow rate. The influence of the relative distance l between the inlet and the structure on η is non-monotonic. To achieve a higher η, the l for the rectangular column, triangular prism, and semi-cylinder should be 0.2–0.3, 0.2–0.3, and 0.3–0.55, respectively. The deflection angles and the ratio of lateral velocity to streamwise velocity of the deflection mainstream decrease with increasing l. H for the rectangular column is higher than that for other shapes. The results are of guiding significance for the layout of barrier structures and for the optimization of water landscapes in practical applications.
... Currently, scholars at home and abroad have conducted a large number of related studies on the impact of cross-river bridges on river channels and achieved more fruitful results. (David et al. 2019) conducted a hydrological simulation assessment of long-term regional bridge scour risk based on physical climate change and applied it in the Lihay River basin; (Tewodros & Abdusselam 2019) used the MIKE21 FM model to assess the risk of bridge scour in the Ayama basin in Turkey modeled the effect of urbanization on flood risk in the Ayamama basin, Istanbul; (Costabile et al. 2015) comparatively analyzed the backwater effects of bridge and no-bridge scenarios based on 1D and 2D river flood models; (Dimitriadis et al. 2016) comparatively assessed the uncertainty in flood mapping based on 1D and quasi-2D hydraulic models; (Zhang et al. 2021) based on MIKE21FM model, simulated the effect of different shaped piers on the flow regime of the river; (Echeverribar et al. 2019) provided a robust two-dimensional model for simulating flood events, which has the ability to avoid instability and makes the model suitable for numerical correction of complex phenomenon simulations (Wang & Jing 2019) studied the effect of bridge piers on flood hazards in the Jialing River basin using the MIKE21 two-dimensional numerical model. (Liu et al. 2020) based on a two-dimensional hydrodynamic model with dynamic numerical simulation of the congestion and scour generated by the current bridge and the bridge to be reconstructed; (Yan et al. 2020) studied the pier front congestion and section average congestion characteristics of double piles under different diameter and flow velocity conditions based on the principle of momentum conservation and hydrodynamic model; (Yu & Zhu 2019) used the Reynolds time-averaged N-S equation and the standard k-ε turbulence model to investigate the local scour of a series of The local scour refinement of double-cylindrical piers was simulated using the Reynolds time-averaged N-S equation and standard k-ε turbulence model. ...
The different shapes of bridge piers across rivers have a great influence on the river water movement, and the study of the influence of pier morphology changes on the water movement characteristics is of great value for bridge design and river flooding. The hydrodynamic model can effectively simulate and predict the changes of river flow patterns, which can provide scientific data support for river management. This paper constructs a hydrodynamic model based on MIKE21 and applies it to the numerical simulation of river hydrodynamics in the lower reaches of the Yellow River, taking elliptical piers as an example, and simulates the effect of the change of pier morphology on the flow velocity, water level and flow field of the river. The results show that the effect of elliptical pier morphology on the flow characteristics of the river channel is significant; under the same flow rate, the congestion value of the pier at the maximum axis ratio is 1.65 times the minimum axis ratio, and the larger the axis ratio, the more serious the congestion; the difference in flow velocity at the maximum axis ratio can reach 2.33 times the minimum axis ratio. HIGHLIGHTS
This paper uses MIKE21 numerical simulation to analyze and study the changes in river congestion and flow patterns caused by bridge construction, and to provide more practical simulation data for the construction of cross-river bridges.;
The Nash efficiency coefficient of 0.94 is highly accurate in the model validation and evaluation.;
The construction of wading piers can modify the water flow characteristics of the river, and the quantity of piers is one of the significant influencing factors. Development of numerical simulation study of various numbers of piers on river flow patterns has significant and profound relevance to river flooding and river stability. A GIS-based Mike21 hydrodynamic model of the lower Yellow River is constructed and applied to the two-dimensional hydrodynamic numerical simulation of the lower Yellow River cross-river bridge section. The effect of the number of bridge piers on the flow regime at different flows is studied, and the mechanisms of changes in flow field, congestion height, and velocity are analyzed. The results suggested that with the growth of the number of piers, the congestion height in front of the bridge increased, but the increase gradually decreased, dropping by 2.22% overall. The average flow rate in front of the bridge has declined, with a gradual reduction of 2.01%. The range of flow field changes gradually expanded; however, the speed of increase in the influence range reduced by 11.85%.
River-crossing bridge engineering will change the hydraulic elements of the river and affect the stability of the river regime. The distance between the bridge piers is one of the most significant influencing factors of the river flow regime. Analyzing the impact of its changes on river flow through numerical simulation methods has significant guiding value for river flood control. Based on GIS (Geographic Information System) and DEM (Digital Elevation Model), this paper constructed the MIKE21 hydrodynamic model. We applied it to the two-dimensional hydrodynamic simulation of a cross-river bridge section in the lower Yellow River. We studied the effect of bridge pier spacing on river flow patterns and analyzed the mechanisms of changes in the flow field, height, and velocity. The results show that under the same incoming water condition, the distance between the bridge piers increases every 20 m, and the size of the backwater in front of the bridge decreases. The rate of change decreases from 9.97 to 1.55%, the flow velocity at the bridge location increases, and the rate of change gradually increases, from 1.13 to 7.01%, the range of flow field increases, and the rate of change decreases progressively, from 3.22 to 1.24%.
