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Mid-flood and mid-ebb tidal flow velocity field of a mean spring tide: (a) mid-flood and (b) mid-ebb.
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A tidal stream energy resource assessment can be achieved through direct measurements of tidal elevations or flow velocities, theoretical formulas, and numerical models. This paper first described the development of renewable energy in China. Then, the tidal stream energy resource in the Qiantang River Estuary was assessed. The present work establi...
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Context 1
... simulated time is a 14.5 day period, to cover the spring-neap tidal cycle. Figure 8 shows the flow velocity vectors at mid-flood and mid-ebb of a mean spring tide. It is appar- ent that the relatively high velocities occur in the Qiantang River Estuary due to influence of a fun- nel-shaped bathymetric narrowing. ...
Context 2
... the validation, the model can be used to assess potential tidal stream energy in the estuary. For this purpose, long-term current predictions are produced. The simulated time is a 14.5 day period, to cover the spring-neap tidal cycle. Figure 8 shows the flow velocity vectors at mid-flood and mid-ebb of a mean spring tide. It is appar- ent that the relatively high velocities occur in the Qiantang River Estuary due to influence of a fun- nel-shaped bathymetric narrowing. Most of the current velocities are greater than 1 m/s, the minimum value for economic operation of a tidal stream power plant. The peak flood velocity is 2.8 m/s, which is approximately 1.3 times the peak ebb velocity of 2.2 ...
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Citations
... The Qiantang River Estuary (QRE), renowned for its dramatic tidal bores [13], serves as a prime example of such complexities. In this estuary, the curvature of the coast amplifies tidal ranges and alters current velocities, significantly affecting hydrodynamic conditions [14]. Therefore, studying the morphological evolution of tidal flats in these geomorphologically complex areas requires advanced analytical methods capable of dissecting the interactions between nature and anthropogenic factors. ...
Tidal flats are dynamic coastal ecosystems continually reshaped by natural processes and human activities. This study investigates the application of Empirical Orthogonal Function (EOF) analysis to the long-term profile evolution of tidal flats along the Jiansan Bend of the Qiantang River Estuary, China. By applying EOF analysis to profiles observed from 1984 to 2023, this study identifies dominant modes of variability and their spatial and temporal characteristics, offering insights into the complex sediment transport and morphological evolution processes. EOF analysis helps unravel the complex interactions between natural and anthropogenic factors shaping tidal flats, with the first three eigenfunctions accounting for over 90% of the observed variance. The first spatial eigenfunction captures the primary trend, while the subsequent two eigenfunctions reveal secondary and tertiary modes of variability. A conceptual model developed in this study elucidates the interplay between hydrodynamic forces and morphological changes, highlighting the rotation and oscillation of tidal flat profiles in response to seasonal variations in hydrological conditions. The findings emphasize the effectiveness of EOF analysis in capturing significant geomorphological processes and underscore its potential in enhancing the understanding of tidal flat dynamics, thereby informing more effective management and conservation strategies for these critical coastal environments.
... Wu et al. (2016) identified the southeast and center of the strait as experiencing maximum flow rates of 4.6 m/s. The evaluation of tidal current energy resources in the Qiantang River Estuary by (Li et al. (2018) indicated the highest power density during the mid-flood and midebb of a typical spring tide cycle to be 11.3 and 5.5 kW/m 2 , respectively. According to research done by Jiang et al. (2021), who looked into tidal kinematic energy over the entire Chinese coast, certain parts of Zhejiang and Fujian have the highest concentration of tidal current resources. ...
... On the basis of KdV equation, the tidal bores' formation, evolution and transition to solitary waves in open channel with varied width and water depth were investigated numerically and analytically (Caputo and Stepanyants, 2003). Also, the two-dimensional numerical model was adopted to calculate and assess the power density of tidal stream energy source in the Qiantang River, which is well-known for generating intensive tidal bores (Li et al., 2018). The turbulent tidal bore above uneven topography was investigated and the results showed that the hydrostatic numerical model had sufficient accuracy to calculate the location and structure of steady and unsteady tidal bore front (Gusev and Lyapidevskii, 2005). ...
Tidal bore is a special and intensive form of flow movement induced by tidal effect in estuary areas, which has complex characteristics of profile, propagation and flow velocity. Although it has been widely studied for the generation mechanism, propagation features and influencing factors, the curved channel will complicate the characteristics of tidal bore propagation, which need further investigation compared with straight channel. In this study, the flume experiments for both undular and breaking bores’ propagation in curved channel are performed to measure the free-surface elevation and flow velocity by ultrasonic sensors and ADV respectively. The propagation characteristics, including tidal bore height, cross-section surface gradient, tidal bore propagation celerity, and flow velocity are obtained for both sides of the curved channel. And three bore intensities are set for each type of tidal bores. The free-surface gradients are consistently enlarged in high-curvature section for undular and breaking bores, but have distinct behaviors in low-curvature section. The spatial distributions of tidal bore propagation celerity and flow velocity are compared between concave and convex banks. This work will provide experimental reference for engineering design of beach and seawall protection, erosion reduction and siltation promotion in estuary areas with the existence of tidal bores.
... When the Qiantang River (QR) tidal bore arrives, the water level suddenly rises by approximately 2 m within seconds; the maximum is more than 3 m. The water flow rapidly changes from ebb tide to flood tide [3]. In the case of a sharp bend in the river or obstruction by buildings, the water column aroused will be more than 10 m. ...
Tidal bores are a natural phenomenon with high flow velocity and destructive potential. A spur dike is a widely used river regulation and embankment protection structure that minimizes erosion, promotes deposition, and protects riverbanks. However, the scouring mechanism around a spur dike under the action of a tidal bore is not fully understood, and accurately estimating the maximum scour depth has always been a challenge, limiting the construction and maintenance of spur dikes in estuarine and marine environments. This study analyzed the scouring characteristics around a spur dike induced by tidal bores via field observation and model experiments. The results show that the scours around a spur dike can be divided into dike head scour and upstream side scour. The scour depth is related to the geometric shape of the spur dike and its surrounding riverbed, hydrodynamic forces, and sediment characteristics. The least squares method obtained the fitting formulas for the depth of the scour at the dike head and upstream side. Overall, the present study indicates an agreement of the scouring characteristics around a spur dike between the field observations and laboratory experiment, and the fitting formulas can be effectively applied to engineering practices of a macro-tidal estuary.
... Wu et al. [55] investigated tidal current energy in the Qiongzhou Strait and discovered that the current speed could reach 4.6 m/s in the southeast and center waters. The tidal current resource in Qiantang River Estuary was assessed by Li et al. [56], who found that the peak power density during the flood and ebb of a spring tide cycle are 11.3 kW/m 2 and 5.5 kW/m 2 , respectively. Gao et al. [57] examined tidal current energy surrounding Hulu Island, China, and recommended two potential locations for tidal farms, with the mean power density of 0.62 kW/m 2 and 1.81 kW/m 2 , respectively. ...
In this study, a numerical investigation of potential sites for tidal current energy extraction is performed in Southern China seas by using the 3D hydrodynamic model FVCOM. The accuracy of the numerical model is validated by using 15-day data from 95 tide stations and 12 current stations. This study identifies 13 potential sites from 6 regions of interest where strong currents and appropriate water depths are suitable for tidal energy development. The modeling results show that the Dongchong Channel of Sansha Bay contains the highest depth-averaged tidal power density, reaching nearly 5000 W/m2. Moreover, the quantitative analysis is performed for different Tidal Current Turbines (TCTs) at the potential sites, considering not only energy yield but also stability of power output. The results indicate that the NNU-300 kW turbine with a rated power of 300 kW and a rotor diameter of 17 m performs the best in most locations in relatively deep water, while the Nova’s M100-D turbine with a rated power of 100 kW and a rotor diameter of 8.5 m is the most appropriate device in relatively shallow water sites. In addition, for most selected types of TCTs, the site H11 near the Fujian coast is the most promising location for future tidal farm development.
... The bathymetry there is quite flat with an average water depth of only 8.0-10.0 m. According to Ref. [88], the maximum flow velocity during flood and ebb might reach 2.8 m/s and 2.2 m/s as shown in Fig. 26, and the maximum energy density exceeded 11.4 kW/m 2 . The flow speed is much higher on the north than the rest areas. ...
... Current velocity distribution in Hangzhou Bay during flood and ebb tides[88] (Image courtesy of the authors; contact by email). ...
Tidal current energy has received extensive attention from both academia and industry in the past decade due to its high power density and strong predictability. Besides Europe and the United States, China has also made tremendous efforts in tidal current energy development, as this abundant ocean renewable resource is expected to provide consistent and clean power for highly-populated coastal cities or remote islands. To evaluate the tidal current resource potential in China, both national assessments and regional investigations have been conducted with different methods and resolutions. However, these evaluation results have not been systematically collected, which are poorly informed to researchers, developers, and investors. At the same time, the conducted assessments sometimes show discrepancies, indicating the necessity of analysing data uncertainty and improving data quality. Under the circumstances, this work presents a review of tidal current resource assessment studies in China, and most existing evaluations for tidal current energy hotspots have been included, classified and compared. Particularly, these regions of interest are further categorised with their exploitability, based on not only theoretical energy reserve estimation, but also local conditions of bathymetry, transportation, policy, etc. According to the assessment results, Zhoushan Archipelago has been considered the most suitable area for large-scale tidal current energy development in China, and the waters nearby Chengshan Cape and Qiongzhou Strait are also with great potential. Furthermore, assessment result uncertainties are analysed, and suggestions on scientific research, technology innovation, and business investment are also proposed for future China tidal current energy development.
... The Qiantang River Basin covers an area of 5,5558 km 2 , with a length of 668 km. The maximum observed tidal range is 9.15 m and the maximum flood velocity is greater than 10 m/s (Li et al., 2018). The tidal bore is now forming near the town of Ganpu (Figure 1c), and recent measurements indicate the celerity of the bore is usually 4-9 m/s (Li et al., 2019), and the normal height of the bore is 1-2 m and the maximum height of a single bore front is about 4 m. ...
The Qiantang River Estuary is a funnel-shaped macrotidal estuary with a famous tidal bore. According to historical documents, many dynasties have recorded the tidal disasters in China. Based on historical data, the spatial and temporal distributions of tidal disasters along the Qiantang River Estuary are investigated and the future trends are projected. The wavelet analysis for the occurrence number of tidal disaster in the Qiantang River Estuary shows that there are periodic oscillations of 5 years, 17 years, 29 years, and 55 years. 55 years is the first principal period. The month distribution mainly concentrates from the 5th to the 9th month of the Chinese lunar calendar, and come to peak in the 7th month. The daily distribution mainly concentrates near the waxing cresent moon and the waning gibbous moon, partly resulted from the lunar force influence. In spatial analysis, the frequency and hot spots show significant regional differences, and have a certain concentration in Hangzhou, Haining, Haiyan and Pinghu. Tidal disasters occurrence coincides with the change of the frequency of seawall construction and coastal reclamations, and it may be the reflection of sea level change.
... Compared with Europe, tidal current energy technology in China has also been rapidly developed (Liu et al., 2017). In recent years, many studies have been carried out on assessing and collecting tidal energy from China's coastal waters (Wu et al., 2017a;Li et al., 2012Li et al., , 2018Liu et al., 2019), and several different types of tidal current turbines have been developed and tested (Zhang et al., 2014). Among different shoreline areas, waters around Zhoushan Archipelago have lots of channels with strong tidal currents, and it is regarded as the most promising place to install China's first national tidal farm in the future (Li et al., 2010;Qian et al., 2019). ...
... The Qiantang River has a catchment area of 55,558 km 2 and is 668 km in length. The observed maximum tidal range is 9.15 m, and the maximum flood velocity is more than 10 m/s (Li et al. 2018). The tidal bore currently forms near the town of Ganpu (Fig. 1c) and has a celerity of 4-9 m/s, a normal height of 1-2 m, and a maximum height (single bore front) of 4 m. ...
Subterranean termites (Odontotermes formosanus Shiraki) that build nests in the soil matrices of earth embankments may adversely affect the stability of these structures in paddy farming regions of southern China. An adult termite nest comprises a primary chamber, fungus gardens, passageways, and other shelter tubes. These porous architectures enable high hydraulic conductivity and rapid groundwater flow. In this study, we performed a field survey to characterize these termite nest architectures and proposed a simulation method that estimates seepage and associated stability in termite-infested earth embankments. Three types of nest architectures—straight, siphon, and string—were investigated in situ. Groundwater flow and its relationship with earth embankment stability were analyzed using a numerical model based on the two-dimensional Richards equation in the HYDRUS software package. Results indicated that the presence of termite nests affected seepage zone geometry and substantially affected its phreatic line, seepage flux, and global and local stabilities of the earth embankment. In the cases examined here, the presence of termite nests resulted in a maximum factor of safety reduction of 17% along the downstream slope. The local instability zones of earth embankment, resulting from clogged termite nest passageways along the downstream slope, were also assessed.
... In China, a number of studies on tidal current energy have been conducted in various domestic waters (Li et al., 2012;Chen et al., 2013;Fang et al., 2015;Wu et al., 2017;Li et al., 2018). Among these, the sea area near Chenshan Cape has been identified as a potential site for exploiting these resources in northern China and has been a research hotspot for the assessment of extractable energy. ...
The sea area east of Chenshan Cape has peak tidal current flows that exceed 2.3 m s⁻¹, which make it a promising site for the development of tidal current energy. Before these resources can be exploited, a comprehensive assessment is needed of the potential environmental impacts of the extraction of this energy. In this paper, we describe our construction of a three-dimensional hydrodynamic model of the waters near Chengshan Cape, and verify the performance of the model using continuous data measured in situ. We modeled the potential impacts of the exploitation of these resources on the flow field by adding a momentum loss term in the governing equation of the model. Simulation results show that an assumed tidal farm with an estimated power output of 20.34 MW would have a significant impact on the surrounding water level, especially next to the farm, where fluctuation could reach 6 cm. The maximum drop in the flow velocity in the wake of the farm was predicted to be more than 0.8 m s⁻¹, and this influence would extend 10 km downstream.
