Hashin Failure Theory Based Damage Assessment Methodology of Composite Tidal Turbine Blades and Implications for the Blade Design     

YU Guo-qing  REN Yi-ru  ZHANG Tian-tian  XIAO Wan-shen  JIANG Hong-yong 《海洋工程》2018,32(2):216-225

A damage assessment methodology based on the Hashin failure theory for glass fiber reinforced polymer (GFRP) composite blade is proposed. The typical failure mechanisms including the fiber tension/compression and matrix tension/compression are considered to describe the damage behaviors. To give the flapwise and edgewise loading along the blade span, the Blade Element Momentum Theory (BEMT) is adopted. In conjunction with the hydrodynamic analysis, the structural analysis of the composite blade is cooperatively performed with the Hashin damage model. The damage characteristics of the composite blade, under normal and extreme operational conditions, are comparatively analyzed. Numerical results demonstrate that the matrix tension damage is the most significant failure mode which occurs in the mid-span of the blade. The blade internal configurations including the box-beam, I-beam, left-C beam and right-C beam are compared and analyzed. The GFRP and carbon fiber reinforced polymer (CFRP) are considered and combined. Numerical results show that the I-beam is the best structural type. The structural performance of composite tidal turbine blades could be improved by combining the GFRP and CFRP structure considering the damage and cost-effectiveness synthetically.  相似文献   

桑沟湾邻近海域岬角潮余流涡对及其产生机理          下载免费PDF全文

周炜  宣基亮  黄大吉 《海洋学研究》2020,38(3):10-20

桑沟湾邻近海域潮余流对该海域物质输运具有重要作用,但由于观测资料不足的限制,该海域潮余流的整体分布状况尚不明确。本文利用22套锚系海流观测资料和高分辨率数值模拟资料,分析了桑沟湾邻近海域潮余流的整体分布特征,并探讨了其产生机理。桑沟湾内潮余流总体上较弱,其邻近海域的潮余流在3个岬角(俚岛,寻山和楮山)附近呈现出显著的潮余流涡对结构,每个岬角的北面存在气旋式潮余流涡,南面存在反气旋式潮余流涡。无论是流速大小还是涡覆盖范围,俚岛和楮山外海潮余流涡对均大于寻山外海的涡对。动力诊断分析表明,岬角附近3对潮余流涡的主要形成机制都是由侧边界摩擦引起的水平剪切作用,底摩擦应力旋度的作用只影响俚岛附近的潮余流涡对,位势涡度守恒的作用都不显著。  相似文献   

红海湾西北海区海流特征分析     

刘广平  何伟宏  邹晓理  王昭正  孙天山 《热带海洋学报》2018,37(5):40-49

利用2008年夏季和冬季的海流资料分析了红海湾西北海区潮流性质、运动形式、涨落潮流特性、余流特征。结果表明: 红海湾西北海区属不规则半日潮海域, 潮流性质属往复流, 大致呈东—西向往返运动, 具有一定的旋转流性质; 平均涨潮流最大可达17.8cm·s^-1, 平均退潮流最大可达19.3cm·s^-1; 实测流受风和地形影响明显。余流受风和地形的影响也比较明显, 在偏北风作用下, 余流流向西偏南; 在偏南风作用下, 余流流向东偏北, 余流最大可达18.9cm·s^-1。潮能主要由东部向西传播至红海湾西北海区, 潮能进入量值可达4.8×10³W·m ^-1。  相似文献   

水平轴潮流能发电装置结构对其水动力性能的影响     

王葛  潘京大  张兴东  李广建  王兵振 《海洋通报》2018,(4):475-480

为研究水平轴潮流能发电装置结构对其水动力性能的影响,运用格子玻尔兹曼(LBM)方法,建立水平轴潮流能发电装置的数值模拟分析模型,对水轮机在不同尖速比工况下的水动力性能进行模拟。将模拟结果与同工况水池拖曳实验得到的数据相对比,二者捕获能系数误差在2%左右,验证了LBM方法的可行性和准确性。在此基础上利用LBM方法研究机舱和立柱结构对水轮机特性的影响,得到其对水轮机捕获效率的影响规律。  相似文献   

Long-term divergent tidal flat benthic community recovery following hypoxia-induced mortality     

C. Van Colen  F. Montserrat  M. Vincx  T. Ysebaert  S. Degraer 《Marine pollution bulletin》2010,60(2):178-84

Macrobenthos recovery after hypoxia-induced mass mortality was assessed in an estuarine tidal mudflat during 3 years. During the first 2 years, a Pearson-Rosenberg type of community recovery took place along with the improving bottom water oxygen conditions. After 3 months, spionid polychaetes became superabundant (i.e. opportunistic peak), followed rapidly by a steep decline (i.e. ecotone point). Subsequently, a moderate increase in species richness and a steep increase in biomass, related to the growth of long-lived species occurred (i.e. transition region). Afterwards, however, the recovering community diverged again from the ambient, undisturbed, sediments due to enhanced recruitment success of long-lived species presumably resulting from the lowered interference from bioturbation during early recovery stages in the disturbed plots. Hence, despite early community recovery may be more or less deterministic, lagged divergent community reassembling may occur at the longer-term, thereby contributing to benthos patchiness in areas which are frequently subjected to disturbances.  相似文献   

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张晶  刘琦 《大地测量与地球动力学》2010,30(6):6-9

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Critical perspectives on the evaluation and optimization of complex numerical models of estuary hydrodynamics and sediment dynamics     

J.R. French 《地球表面变化过程与地形》2010,35(2):174-189

Numerical hydrodynamic and sediment transport models provide a means of extending inferences from direct observation and for advancing our understanding of estuarine processes. However, their parametric complexity invites questions concerning the extent to which model output can be assessed with respect to data. This paper examines the basis for evaluating the performance of complex hydrodynamic and sediment transport models, with reference to a case study of a muddy meso‐tidal estuary. Sophisticated and computationally‐intensive models should be evaluated using robust objective functions, but conventional measures of fit and model efficiency invoke restrictive assumptions about the nature of the errors. Furthermore, they offer little insight into causes of poor performance. Optimization of tidal hydrodynamic models can usefully combine conventional performance measures with harmonic analysis of modelled shallow water tidal constituents that are diagnostic of the interactions between tidal propagation, bathymetry and bottom friction. Models with similar efficiencies can thus be distinguished and likely sources of error pinpointed. Hydrodynamic models have a predictive power that is rooted in a more‐or‐less complete representation of the physical processes and boundary conditions that are well‐constrained with respect to data. In contrast, fine sediment models rely on a less complete conceptualization of a broader set of processes and, crucially, have a parametric complexity that is unmatched by the quantity and quality of observational data. Their performance as measured by conventional objective functions is weaker and it is important to match the structural complexity of model errors with analyses that can localize the scales and times of poor performance. Wavelet analysis is potentially useful here as a means of identifying aspects of the model that need improvement. The context in which such models are deployed is also important. Used heuristically, what might otherwise be dismissed as weak models can still provide mechanistic support for empirically‐derived inferences concerning specific aspects of system behaviour. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Tide‐modulated hyperpycnal flows off the Huanghe (Yellow River) mouth,China     

Houjie Wang  Naishuang Bi  Yan Wang  Yoshiki Saito  Zuosheng Yang 《地球表面变化过程与地形》2010,35(11):1315-1329

Few hyperpycnal flows have ever been observed in marine environments although they are believed to play a critical role in sediment dispersal within estuarine and deltaic depositional systems. The paper describes hyperpycnal flows observed in situ off the Huanghe (Yellow River) mouth, their relationship to tidal cycles, and the mechanisms that drive them. Simultaneous observations at six mooring stations during a cruise off the Huanghe mouth in the flood season of 1995 suggest that hyperpycnal flows observed at the river mouth are initiated by high concentrations of sediment input from river and modulated by tides. Hyperpycnal flows started near the end of ebb tides, when near‐bottom suspended sediment concentration (SSC) increased rapidly and salinity decreased drastically (an inverse salt wedge). The median grain size of suspended particles within the hyperpycnal layer increased, causing strong stratification of the suspended sediments in the water column. Towards the end of flood tides, the hyperpycnal flow attenuated due to frictions at the upper and lower boundaries of the flow and tidal mixing, which collapsed the stratification of the water column. Both sediment concentration and median grain size of suspended particles within the bottom layer significantly decreased. The coarser sediment particles were deposited and the hyperpycnal flows stopped. The intra‐tidal behaviors of hyperpycnal flows are closely associated with the variations of SSC, salinity, and stratification of the water column. As nearly 90% of riverine sediment is delivered to the sea during the flood seasons when hyperpycnal flows are active, hyperpycnal flows at the Huanghe mouth and the river's high sediment loads have caused rapid accretion of the Huanghe delta. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Coupling mechanisms in double sandbar systems. Part 1: patterns and physical explanation     

Bruno Castelle  B. G. Ruessink  Philippe Bonneton  Vincent Marieu  Nicolas Bruneau  Timothy D. Price 《地球表面变化过程与地形》2010,35(4):476-486

Crescentic sandbars and rip channels along wave‐dominated sandy beaches are relevant to understand localized beach and dune erosion during storms. In recent years, a paradigm shift from hydrodynamic template models to self‐organization mechanisms occurred to explain the formation of these rhythmic features. In double sandbar systems, both the inner‐ and outer‐bar rip channels and crescentic planshapes are now believed to be free instabilities of the nearshore system arising through self‐organization mechanisms alone. However, the occasional occurrence of one or two inner‐bar rip channels within one outer‐bar crescent suggests a forced, morphologically coupled origin. Here we use a nonlinear morphodynamic model to show that alongshore variability in outer‐bar depth, and the relative importance of wave breaking versus wave focussing by refraction across the outer bar, is crucial to the inner‐bar rip channel development. The coupling patterns simulated by our model are similar to those observed in the field. Morphological coupling requires a template in the morphology (outer‐bar geometry) which, through the positive feedback between flow, sediment transport and the evolving morphology (that is, self‐organization) enforces the development of coupling patterns. We therefore introduce a novel mechanism that blurs the distinction between self‐organization and template mechanisms. This mechanism may also be extended to explain the dynamics of other nearshore patterns, such as beach cusps. The impact of this novel mechanism on the alongshore variability of inner‐bar rip channels is investigated in the companion paper. Copyright © 2010 John Wiley and Sons, Ltd.  相似文献   

近期长江北支口门圆陀角附近潮滩地貌动态变化   总被引：2，自引：0，他引：2  

张振克  谢丽  丛宁  李瑛  王秀玲  何华春 《地理研究》2010,29(5):909-916

圆陀角位于长江北支岸线与江苏海岸线的交会处,独特的互花米草潮滩、淤泥质光滩环境和复杂的河海沉积动力,决定了潮滩地貌对海洋环境变化的响应具有敏感性。由于大规模的围垦,圆陀角附近过去40年来海岸线向东推进了6km。根据2006年以来多次的野外调查和室内粒度与钻孔岩芯的¹³⁷Cs分析, 2006年以来圆陀角附近潮滩淤积明显加强,由¹³⁷Cs时标估算的互花米草滩多年平均沉积速率为2.3cm/a, 2006~2008年观测到的互花米草滩淤积速率>4cm/a,粉砂淤泥质光滩的淤积速率更高;圆陀角风景区内互花米草滩前缘陡坎在风暴潮影响下侵蚀后退,并因粉砂淤泥质光滩的快速淤长而消亡,圆陀角附近潮滩地貌动态是对人类围垦活动、风暴潮与潮汐海洋动力的综合响应,互花米草与光滩快速淤积是近期圆陀角附近潮滩地貌演化的主要特点。  相似文献