A Boussinesq-type wave driver for a morphodynamical model to predict short-term morphology     

Ivo Wenneker  Ap van Dongeren  Jamie Lescinski  Dano Roelvink  Mart Borsboom 《Coastal Engineering》2011

The prediction of near-shore morphology on the time scale of a storm event and the length scale of a few surf zone widths is an active area of research. Intense wave breaking drives offshore-directed currents (undertow) carrying sediment seawards, resulting in offshore bar migration. In contrast, higher order nonlinear properties, such as wave asymmetry (velocity skewness) and velocity asymmetry, are drivers for shoreward transport. These wave processes are included in phase-resolving models such as Boussinesq-type wave models (e.g., TRITON). Short-wave averaging in the wave model yields wave-induced forces (e.g., radiation stress gradients) and a wave asymmetry term. The wave-induced forces are used in a hydrostatic model (e.g., Delft3D flow module) to drive the current and undertow, resulting in a 3D velocity profile. The wave model and hydrostatic model are coupled online with a morphodynamic model (e.g., Delft3D morphology module). The latter computes, based on the 3D flow profile and the wave asymmetry term, the sediment transport and performs the bathymetry updates. The updates are transferred directly back to the hydrodynamic models. The coupling of the wave model TRITON and the Delft3D modules is validated by comparing against extensive laboratory data sets (LIP and Boers) and a field case (Duck94), and show a good performance for the hydrodynamics and a reasonable/fair performance for the bar movements.  相似文献   

Evolution of wave shape over a low-crested structure     

Qingping Zou  Zhong Peng 《Coastal Engineering》2011

This paper investigates the evolution of wave shape over a low-crested structure (LCS) using a 2-D RANS-VOF model. The model predictions of surface elevation and wave skewness and asymmetry are in good agreement with the recent measurements collected in a small scale wave channel at the University of Cantabria (UCA). The empirical formulae relating wave skewness and asymmetry to local Ursell number by Peng et al. (2009) have been extended to include the effect of wave reflection and the ramp in front of LCS and a wider range of Ursell number in the present study. In the presence of LCS, wave skewness decreases slightly above the seaward slope, then increases rapidly up to a maximum value above the structure crest, and decreases drastically above the leeward slope. Wave asymmetry decreases sharply above the seaward slope to a negative minimum value at the structure crest, and then increases rapidly to a positive value above the leeward slope. Our bispectral analysis indicates that sum interactions increase skewness and decrease asymmetry while difference interactions have opposite effects and that the former dominate above the seaward slope and on the structure crest but the latter dominate above the leeward slope of LCS. The observed wave shape evolution over a LCS can be attributed to the changes in the interplay of sum and difference interactions. We found that incident wave height and wave period, relative structure freeboard, structure crest width and structure porosity are the controlling factors for wave shape evolution over LCS. This study provides new insights on the role of wave skewness and asymmetry in the breakwaters stability and sediment transport around the structure and on the beaches behind it.  相似文献   

On the predictive skill of morphodynamic models for onshore sandbar migration     

Viyaktha Hithaishi Hewageegana  Alberto Canestrelli 《地球表面变化过程与地形》2021,46(9):1692-1712

A simplified process-based approach for evaluating onshore sandbar migration is presented in this study. This approach takes wave-averaged parameters as input and computes sediment transport processes using a reconstructed intra-wave orbital velocity signal. The proposed method guarantees good predictive skills for multiple onshore sandbar migration cases without an ad hoc calibration for each scenario. The study differs from previous onshore sandbar migration models, where calibration and testing are performed on just one or few events, and model assessment for uncalibrated realizations is rarely carried out. The present version of the model only addresses onshore sandbar migrations. For the onshore migration cases analyzed, the model has better predictive skills than state-of-the-art morphodynamic models (XBeach and Unibest-TC).  相似文献   

Influence of sieving time on the efficiency and accuracy of grain‐size analysis of beach and dune sands     

Jorge Román‐Sierra  Juan j. Muñoz‐perez  Marina Navarro‐Pons 《Sedimentology》2013,60(6):1484-1497

Grain size is a fundamental property of sediments and is commonly used to describe sedimentary facies and classify sedimentary environments. Among the various conventional techniques utilized to determine grain‐size frequency distributions, sieving is the most widely applied procedure. The accuracy of such analyses is, among other factors, strongly dependent on the sieving time. However, despite a substantial amount of research in this field, optimal sieving times for different types of sediments have, to date, not been established. In this article, the influence of sieving time on grain‐size analyses of medium‐grained microtidal and mesotidal beach and dune sands has been determined. To assess the precision of important textural parameters, such as median grain size, sorting, skewness and kurtosis, an error analysis was carried out for different sieving times (2, 5, 10, 15 and 20 minutes). After calibrating the analytical and sampling methodologies, significant deviations were registered when sieving time was less than 10 minutes. However, such deviations were very small and grain‐size distributions remained almost identical for sieving times of 10 minutes and longer, relative errors being as low as 0% in some cases.  相似文献   

改进的UKF在GPS/INS组合导航中的应用     

刘庆元  郝立良  黄书捷  朱山昱 《测绘科学技术学报》2014,(5)

在GPS/INS组合导航中,传统UKF(Unscented Kalman Filter)计算量大,无法满足实时性要求。而且当动力学模型受到异常扰动误差影响时,其精度与稳定性易受到影响。针对以上问题,利用最小偏度单形采样策略降低UKF计算量以提高精度;通过自适应调整过程噪声以降低动态异常扰动误差对UKF精度与稳定性的影响。由此提出了一种改进UKF算法,用于GPS/INS组合导航。仿真实验结果表明,改进UKF算法用于GPS/INS组合导航的精度要优于UKF算法。  相似文献   

随机波浪中畸形波在三维岛礁地形上的试验研究     

邹丽  王爱民  王振  裴玉国  刘小龙 《海洋学报(英文版)》2019,38(6):92-99

在试验水池中，开展了波浪在岛礁地形上演化问题的研究。首先在实验水池中建立了西太平洋某岛礁地形的模型，然后采用改进的JONSWAP谱，由造波机产生不同周期、波高的随机波浪。试验中观察到了不同类型畸形波生成的过程及不同波面形态的畸形波。对偏度、峰度及水深与畸形波要素H_m/H_s（H_m表示波列中的最大波高， H_s为有效波高）的关系进行了详细的分析，同时，对畸形波波高H_fr与偏度的关也进行了分析。通过对试验结果分析，发现峰度与畸形波要素i>H_m/H_s呈正相关， H_fr增大时相应的偏度也会呈现增大的趋势。此外，水深的变化剧烈时（如斜坡、海山位置）有助于畸形波的发生。  相似文献   

乐清湾内外潮波变形及不对称性分析     

童朝锋  安福伟  章家保  曲开成  孟艳秋 《海洋工程》2020,38(3):113-123

海湾内外的潮波变形及其不对称性影响海湾内外动力输送和水体交换。利用乐清湾内外共9个测站连续潮位进行调和分析,得到该海湾内外各分潮变化规律,利用潮不对称性偏度计算方法确定湾内外潮汐不对称性时空变化特征,比较了主要分潮组合对潮汐不对称性的贡献度,通过数值研究探讨了湾内偏度比湾外偏度值更小的主要成因,分析了湾内外围垦工程对潮不对称偏度的影响。研究发现:乐清湾内潮汐不对称偏度值为负,表现为落潮占优,同期湾外洞头站偏度值为正,与邻近瓯江、飞云江河口的潮不对称偏度变大、表现涨潮占优的变化规律相反;湾外沿岸各站偏度由东北向西南逐渐增大,由落潮占优向涨潮占优变化;潮汐不对称性偏度呈周期性变化,分析确定M2-M4、M2-S2-MS4分潮组合对潮不对称贡献大,该海域潮汐不对称的强度主要由浅水分潮振幅控制,而相对相位则决定潮汐不对称的方向;数值研究探讨表明,湾内大范围的浅滩地形是其潮汐不对称落潮占优的主要原因,围垦将削弱湾内的落潮占优。  相似文献   

APPROXIMATE REPRESENTATION OF THE p-NORM DISTRIBUTION   总被引：1，自引：0，他引：1  

SUN Haiyan 《地球空间信息科学学报》2001,4(3)

1　ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｓｕｒｖｅｙｉｎｇｄａｔａｐｒｏｃｅｓｓｉｎｇ ,ｉｔｉｓｏｆｔｅｎｓｕｐｐｏｓｅｄｔｈａｔｏｂｓｅｒｖａｔｉｏｎａｌｅｒｒｏｒｓｄｉｓｔｒｉｂｕｔｅｎｏｒｍａｌｌｙ .Ｉｆｏｂ ｓｅｒｖａｔｉｏｎｓｃｏｍｅｆｒｏｍｔｈｅｎｏｒｍａｌｄｉｓｔｒｉｂｕｔｉｏｎａｌｃｌａｓｓ ,ｔｈｅｍｅｔｈｏｄｏｆｌｅａｓｔｓｑｕａｒｅｓｃａｎｇｉｖｅｔｈｅｍｉｎｉ＿ＰｒｏｊｅｃｔｓｕｐｐｏｒｔｅｄｂｙｔｈｅＳｕｓｔｅｎｔａｔｉｏｎＰｌａｎｆｏｒＯｕｔｓｔａｎｄｉｎｇＴｅａｃｈｅｒｓｏｆＡ…  相似文献   

Spreading-rate-dependent magnetization of the oceanic lithosphere inferred from the anomalous skewness of marine magnetic anomalies   总被引：1，自引：0，他引：1  

J. Dyment  J. Arkani-Hamed 《Geophysical Journal International》1995,121(3):789-804

  相似文献   

1957-2000年东北地区春季极端气温变化及其与北极涛动的关系   总被引：14，自引：2，他引：12  

王冀  江志红  张海东  娄德君 《气候变化研究进展》2007,3(1):41-045

利用东北地区32个测站1957-2000年逐日气温资料,分析了东北春季极端气温指数的变化特征及其与同期和前期北极涛动指数的关系。结果表明：春季日气温距平值基本上是由高纬向低纬、由东向西增加;44 a来日气温距平强度变化呈现正趋势,春季的冷日和冷夜呈减少趋势,暖日和暖夜呈增加趋势。东北春季气温与春季北极涛动（Arctic Oscillation, AO）在年际时间尺度上具有很强的正相关性,AO和极端气温指数也存在着相同的变化周期和突变时间。  相似文献