Analysis of Tidal Current Energy Potential in the Major Channels of the Bohai Strait Based on Delft3D

The utilization and development of tidal current energy can help alleviate the current energy shortage,improve the global ecological environment,and maintain sustainable development.In this study,numerical simulation is carried out on a rectangular grid using Delft3D.The tidal current energy potential of the major channels in the Bohai Strait is further simulated and estimated by comparing the simulated and measured data.Results show that the flow module in Delft3D has good modeling ability for the assessment of tidal current energy potential.The average flow velocity,maximum flow velocity,and energy flow density are consistent.The Laotieshan Channel,located in the northern part of the Bohai Strait,shows a large tidal current energy potential.The maximum flow velocity of this channel can reach 2 m s-1,and the maximum energy flow density can exceed 500 W m-2.The tidal current energy in the Laotieshan Channel is more than 10 times that in other channels.Therefore,this study advocates for the continued exploration and exploitation of the tidal current energy resources in the Laotieshan Channel.

Numerical Investigation of Flow Motion and Performance of A Horizontal Axis Tidal Turbine Subjected to A Steady Current

Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k-ε model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.

Assessment of Tidal Range Energy Resources Based on Flux Conservation in Jiantiao Bay, China

La Rance Tidal Range Power Station in France and Jiangxia Tidal Range Power Station in China have been both long-term successful commercialized operations as kind of role models for public at large for more than 40 years. The Sihwa Lake Tidal Range Power Station in South Korea has also developed to be the largest marine renewable power station with its installed capacity 254 MW since 2010. These practical applications prove that the tidal range energy as one kind of marine renewable energy exploitation and utilization technology is becoming more and more mature and it is used more and more widely. However, the assessment of the tidal range energy resources is not well developed nowadays. This paper summarizes the main problems in tidal range power resource assessment, gives a brief introduction to tidal potential energy theory, and then we present an analyzed and estimated method based on the tide numerical modeling. The technical characteristics and applicability of these two approaches are compared with each other. Furthermore, based on the theory of tidal range energy generation combined with flux conservation, this paper proposes a new assessment method that include a series of evaluation parameters and it can be easily operated to calculate the tidal range energy of the sea. Finally, this method is applied on assessment of the tidal range power energy of the Jiantiao Harbor in Zhejiang Province, China for demonstration and examination.

Evaluation of tidal stream energy and its impacts on surrounding dynamics in the Eastern Region of Pingtan Island, China

Using an improved FVCOM numerical model, combined with the momentum-sinking scheme based on the structural characteristics of specific turbines, this study analyzed the temporal and spatial distributions of tidal energy resources before and after the deployment of tidal turbines near Pingtan Island, China. Considering factors such as the distribution of tidal stream energy, bathymetry, topography, and the design parameters of the turbines, an appropriate location for a demonstration tidal turbine was selected and the corresponding energy resource was evaluated. Several sites with strong tidal streams were considered： south of the northern cape, east of the southem cape, and the southern end of Haitan Bay. The former was thought most suitable for the deployment of a tidal energy turbine, with projected power generation for approximately 470 h per month. The average power of this demonstration was about 2.4 kW, and the annual electricity output was approximately 17.47 MWh. The intervention of the turbine device had little influence on the near-field tidal stream or water level. The tidal stream was reduced slightly in the area south of the northern cape, although the effect weakened further from the turbine. Conversely, the velocity increased slightly on both sides of the demonstration site. The difference in current speed with and without the turbine was greater at slack tide than still tide. The influence of turbine operation on water level was minor. The method adopted in this study can be considered a reference for the selection of sites for the demonstration of tidal stream energy. However, the method is unable describe the dynamic characteristics of the turbulent flow surrounding the deployed turbines, which has an important role regarding the optimal designs of the turbine blade and pile foundations. Therefore, we will continue to work to improve this model in future research.

Assessment of the Tidal Current Energy Resources and the Hydrodynamic Impacts of Energy Extraction at the PuHu Channel in Zhoushan Archipelago,China

An unstructured model FVCOM(The Unstructured Grid Finite Volume Community Ocean Model)with sink momentum term was applied to simulate the tidal current field in Zhoushan Archipelago,China,with focus on the region named PuHu Channel between Putuo Island and Hulu Island.The model was calibrated with several measurements in the channel,and the model perform-ance was validated.An examination of the spatial and temporal distributions of tidal energy resources based on the numerical simula-tion revealed that the greatest power density of tidal energy during spring tide is 3.6kWm^(−2)at the northern area of the channel.Two parameters were introduced to characterize the generation duration of the tidal array that causes the temporal variation of tidal current energy.The annual average available energy in the channel was found to be approximately 2.6MW.The annual generating hours at rated power was found to be 1800 h when the installed capacity of tidal array is approximately 12MW.A site for the tidal array with 25 turbines was selected,and the layout of the array was configured based on the EMEC specifications.Hydrodynamic influence due to the deployment of the tidal array was simulated by the modified FVCOM model.The simulation showed that the tidal level did not significantly change because of the operation of the tidal array.The velocity reduction covered a 2km^(2)area of the downstream the tidal array,with a maximum velocity reduction of 8cms−1 at mid-flood tide,whereas the streamwise velocity on both sides of the farm increased slightly.

Estimation of Annual Energy Output from BCM Tidal Barrage and the Corresponding Marine Environmental Impact

Based on the finite-volume coastal ocean model （FVCOM）, a three-dimensional numerical model FVCOM was built to simulate the ocean dynamics in pre-dam and post-dam conditions in Bachimen （BCM）. The domain decomposition method, which is effective in describing the conservation of volume and non-conservation of mechanical energy in the utilization of tidal energy, was employed to estimate the theoretical tidal energy resources and developable energy resources, and to analyze the hydrodynamic effect of the tidal power station. This innovative approach has the advantage of linking physical oceanography with engineering problems. The results indicate that the theoretical annual tidal energy resources is about 2x 108 kwh under the influence of tidal power station; Optimized power installation is confirmed according to power generation curve from numerical analysis; the developable resources is about 38.2% of theoretical tidal energy resources with the employment of one-way electricity generation. The electricity generation time and power are 3479 hours and 2.55~104KW, respectively. The power station has no effect on the tide pattern which is semi-diumal tide in both two conditions, but the amplitudes of main constituents apparently decrease in the area near the dam, with the ME decreasing the most, about 62.92 cm. The tidal prism shrinks to 2.28×107 m3, but can still meet the flow requirement for tidal power generation. The existence of station increases the flow rate along the waterway and enhances the residual current. There are two opposite vortexes formed on the east side beside the dam of the station, which leads to pollutants gathering.

流动控制组合对潮流能水轮机翼型水动力学的特性影响研究

为全面提升潮流能水轮机叶片的水动力学性能,将格尼襟翼(GF)和涡流发生器(VGs)的附加件组合引入到潮流能水轮机领域,研究附加件组合对改善水轮机叶片水动力性能的作用机理。以NACA4418翼型为研究对象,分别建立加装格尼襟翼、涡流发生器和二者流动控制组合的水轮机翼型三维模型,应用数值模拟方法研究流动控制组合对水轮机叶片水动力性能的影响机理。结果表明:安装GF可有效提高翼型段的升力系数,但会降低翼型的失速角;安装VGs可抑制翼型段吸力面的流动分离、增大翼型段的失速角,但攻角越小水动力学性能改善效果越不明显;GF和VGs的流动控制组合则可将二者优势充分结合,在全面提高翼型段升力系数的同时,还可抑制翼型表面的流动分离、增大翼型的失速角,从而获得最佳的流动控制效果。

基于FVCOM的普陀山潮流能试验区数值模拟

国内外关于潮流能试验场小范围海域流场特性研究中,缺乏高精度的数学模型模拟真实环境下的水动力特性。本文基于非结构化网格的有限体积海洋数值模型(Finite-Volume Coastal Ocean Model,FVCOM),建立舟山及普陀山-葫芦岛潮流能试验场水域潮汐潮流数值模型,采用大范围区域潮位验证率定模型后得到更精确的小范围开边界条件嵌套小范围区域进行潮流计算。通过4个测站大、小潮的拟合数据和实测潮位、潮流流速、潮流流向数据进行对比,调整装置附近局部区域底摩阻取值,从而概化装置的影响,同时对小范围的潮波传播规律及流场水动力特性进行分析。结果表明:潮流能试验区所处海域潮汐类型为不规则半日潮,潮流以往复流为主;潮流运动传播主要方向为SSE—NNW向,该海域潮流特性空间差异明显;左岸龙南礁内湾区涨潮时呈逆时针传播,落潮时漩涡反向,右侧大龙山咀湾区涨落潮时均无明显涡旋。本研究可以为试验场海域潮流能发电装置阵列布放优化提供理论参考。

Numerical study of a guide-vane-augmented vertical darrieus tidal-currentturbine

It is reported that the augmented vertical axis turbine (VAT) has a better operating performance. A guide-vane type augmentation is proposed in this study, with a simpler outline and a better adaptability to various directions of the incident water flow, as compared to the duct-type diffuser. A 2?D numerical model based on the computational fluid dynamics software ANSYS-Fluent is established and validated by experimental data. It is found that the guide vanes could narrow the flow path together with the VAT rotor and increase the flow velocity around the blades. The fluctuation of the instantaneous torque output is significantly reduced by using the guide-vane stator. The numerical results indicate that a four blades setup is suitable for the stator and the chord length of the guide vane should be equal to that of the rotor blade. The gap between the stator and the rotor is suggested to be a quarter of the chord length of the rotor blades. The non-zero pitch angle of the guide vane is found to have negative effects on the torque and the power output. The averaged power and torque coefficients for three non-zero directional angles of the incident flow are approximately 30% lower than those for the zero-directional angle.

阿基米德螺旋水轮机性能分析

为了探究阿基米德螺旋水轮机(ASHT)的性能特点,对5种具有不同旋叶倾角的ASHT进行计算流体动力学(CFD)和单向流固耦合数值模拟。研究结果表明:5种ASHT的峰值功率系数均介于低尖速比范围内,其中角度组合为30-45-60的ASHT具有最佳的峰值功率系数;具有大旋叶倾角的ASHT具有更宽泛的尖速比范围和更大的推力系数,其峰值功率系数对应的尖速比也移动到较大的位置;具有大旋叶倾角的ASHT具有更强的流动堵塞效应和较大的波动幅度;在水动力、重力及自身旋转效应的共同作用下,ASHT所受载荷会出现周期性波动。研究成果可供ASHT的优化设计和推广应用参考。

潮流能水轮机流场特性的数值与实验研究

通过数值模拟和模型实验相结合的方式,研究水轮机近域的流场特性对其水动力性能的影响,分析远域下不同入流速度和尖速比等因素对尾流场特性的影响。研究结果表明,在设计尖速比下,水轮机能量转换效率的数值模拟结果(0.37)与实验结果(0.36)的误差为0.3%,水轮机阻力系数的数值模拟结果(0.73)与实验结果(0.76)的误差为-4%,验证了数值模拟方法的准确性;水轮机梢部存在明显的三维流动现象,水轮机盘前梢部存在由叶根流向叶梢的径向流速(0.24 m/s),盘后梢部存在由叶梢流向叶根的径向流速(0.14 m/s),该叶片梢部尾流区的“下洗”流速导致水轮机能量转换效率下降;入流速度不会对尾流区轴向速度的恢复产生显著影响;在近尾流区(距离盘面小于5D)随尖速比的增加,尾流区轴向速度恢复呈逐渐降低的趋势,而在距离水轮机盘面超过10D之后,尖速比不会对尾流轴向速度恢复产生明显影响,但尖速比的增加会使梢涡存在时间变短,梢涡破碎的位置更靠近水轮机盘面。

渤黄东海潮能通量与潮能耗散

利用同化高度计资料和沿岸验潮站资料对潮汐数值模式进行同化,根据同化后的数值模式结果,对渤黄东海中的潮能通量和潮能耗散进行了研究。M2分潮从太平洋进入渤黄东海的潮能为122.499GW,占4个主要分潮进入总量的79%。黄海是半日分潮潮能耗散的主要海区。全日分潮则主要耗散在东海。全日分潮在遇到陆坡的阻挡以后有一部分潮能沿着冲绳海槽向西南传播,并有一部分潮能反射回太平洋,其中O1分潮通过C3断面反射回太平洋的潮能,约占其传入东海潮能的44%。

水平轴潮流能水轮机设计与数值模拟

为提高潮流能利用效率,基于叶素-动量理论(BEM),给出了Wilson模型在水平轴潮流能水轮机设计上的应用。采用CFD技术计算对设计的水轮机进行水动力特性分析,计算其在不同叶尖速比下的功率特性。在此基础上,对叶片沿展长方向的功率分布和三维绕流特性进行分析,并采用二维计算方法预测对应三维工况下各截面处的流场特性。计算结果表明,水轮机的工作特性满足对功率和效率的要求,说明了设计方法的可靠性;同时绕流特性分析也显示了二维模拟的局限性,尤其在叶根、叶尖部位失真较大,这说明三维效应对水轮机输出功率和流场性能有着显著的影响。

印度尼西亚海域潮波的数值研究

基于ROMS模式构建了模拟区域为(15.52°S-7.13°N,110.39°~134.15°E)水平分辨率为2′的潮波数值模式,分别模拟了印尼海域M2、S2、K1、O1四个主要分潮。模拟结果与29个卫星高度计交叠点上的调和常数进行比较,符合较好。M2分潮的振幅均方根差为3.4cm,迟角均方根差为5.9°;S2分潮的振幅均方根差为1.7cm,迟角均方根差为6.3°;K1分潮振幅均方根差为1.1cm,迟角均方根差为5.8°;O1分潮振幅均方根差为1.2cm,迟角均方根差为4.4°。M2、S2、K1、O1分潮向量均方根差分别为3.8cm、2.4cm、1.9cm和1.3cm,模拟结果的相对偏差在10%左右。根据计算结果分析了印尼海域的潮汐特征及潮能传播规律,结果显示:爪哇海以外的印尼海域主要为不规则半日潮区;全日潮潮能主要由太平洋传入印尼海域,而半日潮潮能则是从印度洋传入印尼海域。

从潮能通量变化看6000a以来长江口的迁移

引入潮能通量变化的概念，将河口区沉积动力环境、泥沙运移与能量变化联系起来，以东中国海三维高精度潮波模拟为基础，对长江口演变进行研究。模拟结果表明，全新世最大海侵以来，科氏力造成的潮能通量变化在长江口、杭州湾、舟山群岛及其外侧始终为负，减少的方向为西北；其负值区界于东经124°以西及北纬28°以北。说明科氏力的作用是使泥沙在长江和杭州湾口及其外侧邻近海域沉积，且沉积体向东南方向发育；在现代长江口外海区沉积动力环境条件下，长江口向东南迁移的范围不会越过东经124°、北纬28°这一界线。舟山群岛造成的潮能通量变化与科氏力的作用一致，但其作用量较小，仅为科氏力的1／50，影响范围也较局限。

海洋潮流能资源的数值估算——以胶州湾口为例

在回顾国际上现有的潮流能资源估算方案基础上,提出利用三维潮流数值模式估算潮流能的思路,并在胶州湾进行了应用。基于普林斯顿海洋模式,建立了胶州湾潮汐潮流三维数值预报模型,对研究海区的潮汐和潮流做出了较为准确的模拟。数值模拟得到的胶州湾口最大可能潮流速度为2m/s,具有一定的潮流能开发潜力;湾口水道上多年平均潮流能蕴藏量为16MW,大潮期间的瞬时值和大潮周日平均值可分别达135和49MW.潮流资料时间序列的长度对潮流能储量的计算结果有较大影响。由于潮流现象具有强烈的时变性和多种周期,估算潮流能的平均储量应积累一年以上的资料为宜。研究表明,潮流数值模式能够提供高时空分辨率的三维潮流数据,有效弥补潮流实测资料稀缺的不足,因而可作为潮流能资源评价的有力工具。

山东省周边海域波浪能资源评估

采用第三代海浪模式SWAN对2001-2010年期间山东省周边海域的波浪状况进行了数值模拟。波浪能数值模拟值与台站观测值的比对结果表明模拟值可靠、实用。分析发现山东省周边海域平均波能流密度以2 000W/m以下为主,低于中国南部海域及欧美沿岸波能流密度。选取12个典型代表点,从波能流密度大小、变化特征、稳定性等角度分析了不同代表点的波浪能情况,发现山东周边波能流密度受气候变化影响近10年来呈上升趋势。综合不同区域波浪能大小及需求情况,建议选取山东半岛东部海域、蓬莱外围岛屿近渤海中部海域和渤海中部海域作为波浪能开发利用的首选区域。其中成山头东部海域波能流密度在冬季高达5 000 W/m,在该季节大部分区域可归为一类资源丰富区。基于此,建议开发利用中小规模的波浪能供电设备或供电设施。

山东半岛近海潮汐及潮汐、潮流能的数值评估

山东半岛电力结构单一,但地理优势显著,因此发展海洋能产业对于半岛能源结构的优化及缓解能源供应不足具有十分重要的意义。本文运用数值模拟手段模拟了渤、黄海的潮流场并进行了模拟结果的验证;对潮汐和潮流进行调和分析并计算了平均潮差、大潮平均最大流速;使用近似公式计算了山东半岛近海海域的潮汐能和潮流能并进行了分级。研究表明,理论装机容量为800kW/km2的区域分布在山东半岛靖海湾以南,属于中等势能区;理论最大功率密度为0.50kW/m2的区域分布在山东半岛数个岬角、海湾处,属于中等动能区。本文通过对山东半岛海洋能的初步评估,为未来海洋能的开发提供理论支持。

北部湾潮波数值研究

利用普林斯顿海洋模式(POM08)建立了北部湾及其临近海区潮汐潮流数值模式,模拟了K1,O1,M2和S2这4个主要分潮,分析了模拟的潮汐和潮流分布特征,从潮波能量的角度讨论了琼州海峡对北部湾潮波系统的影响,并给出北部湾潮能的耗散情况。研究表明,北部湾是典型的全日潮海区,K1和O1分潮在南部湾口形成半个旋转潮波系统,无潮点位于越南顺安附近岸边。琼州海峡中的欧拉潮汐余流为西向流,潮余流造成的水通量约为0.034×106m3/s;余流出海峡西口后,先折向北,然后转向南流出湾外。研究海区中两个强潮流区分别位于琼州海峡和海南岛的西侧,同时这也是两个潮能的高耗散区。北部湾的潮能自南部湾口由外海传入,通过西口涌入琼州海峡,到达海峡东口时日潮波的能量已基本耗散殆尽,在海峡内耗散的4个分潮的潮能约为3.33 GW,相当于北部湾潮能耗散量的35%左右。数值试验表明,琼州海峡作为潮能耗散的重要海区,其存在对于北部湾潮波系统的形成具有较大影响。计算了底边界潮能耗散,结果表明在北部湾和琼州海峡,底边界耗散的潮能分别占该海区总耗散的83%和80%。

海湾内外的动态水位差模拟研究——一种全新的潮汐能开发方式的探索

首次提出了一种全新的海湾潮汐能开发方式——利用海湾内外的动态水位差进行潮汐能发电。原理是利用潮波到达海湾底部和海湾外部的相位不一致性,形成了海湾内外动态水位差,可作为潮汐能发电水头。并构建了一个理想潮汐能海湾进行水动力数值模拟研究,模拟结果显示该新型的潮汐能是存在的,且相比传统潮汐能利用方式对海湾水动力环境和通航影响更小。