共查询到18条相似文献，搜索用时 125 毫秒
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基于前人对无植物河道河相关系研究方法及研究成果,本文遵循仙农熵(Shannon Entropy)理论,利用最大熵原理和变分法,给出考虑植物因子影响的河相关系系数动态表达式,并利用室内物理模型试验所观测的数据对该公式进行敏感性分析和验证,得到比较满意的理论结果. 相似文献
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在河流动力学理论研究中,已有的河相关系式大多是经验半经验性质的,往往不能明确地表达因素的影响,应用时具有很大的局限性.在能量均衡关系的基础上,利用仙农熵的理论,对影响沙质河床稳定河相关系的因素进行了探讨.通过理论分析,认为在取得所测河段上下边界测点相关资料后,用最大熵原理和变分法可以推导出稳定的河相关系式,最后通过试验对所得公式验证其合理性,认为其在计算试验区间任何时刻河相关系系数,均得到较好的吻合结果. 相似文献
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最大熵原理应用于海浪波高分布的研究 总被引：5，自引：0，他引：5
利用最大熵原理从理论上推导出波高的最大熵分布,在此基础上研究了状态参量对波高分布和波高熵的影响。影响最大熵分布的因子是平均波高和状态参量,不同海况对应的状态参量是不同的。利用波高实测资料,得出3种不同海况下的最大熵分布,通过比较发现最大熵分布很好地符合实测数据。把最大熵分布与目前广泛应用的瑞利分布作了比较,结果表明,最大熵分布有2个优点：没有对波高作出任何限制性假定和能够描述不同海况下的波高分布。 相似文献
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以野外样方调查数据为基础,详细调查了海城河河岸带植物群落的组成,种类和外貌,应用重要值计算了海城河河岸带植物丰富度指数、多样性指数、均匀度指数、优势度指数,并分析了其物种的多样性差异,从而为海城河河岸带的生态修复提供理论和技术依据。结果表明:海城河河岸带植物群落20个样方中共有23科60属80种,物种组成以菊科、禾本科、蓼科、莎草科、蔷薇科植物为主,植物种类以芦苇、朝鲜碱茅、中华结缕草、金盏银盘、抱茎苦荬菜、黄花蒿、灯心草、反枝苋、狗尾草等为主。海城河河岸带植物群落结构简单,物种组成较少。群落物种多样性水平较低,从多样性指数的数量特征来看,丰富度指数的变化范围为4.00～16.00,Pielou均匀度指数的变化范围为0.52～0.93,Simpson多样性指数的变化范围为0.45～0.84,Shannon-Wiener多样性指数的变化范围为0.87～2.18,Simpson优势度指数的变化范围为0.17～0.55。海城河河岸带受到人为活动干扰,如农业生产、挖沙等人为活动干扰降低了群落多样性水平。 相似文献
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淹没植物对河道糙率的影响 总被引：1，自引：0，他引：1
基于河道水动力及植物柔性变形分析,建立淹没状态下的植物河道糙率计算的理论关系,同时,利用试验资料及理论分析成果,进一步获得了植物河道糙率的附加值,借此可以分析与评价河道植物对水流阻力的影响程度. 相似文献
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影响胶州湾海域海水水质的主要污染源分析——李村河及其主要支流流域水质现状评价 总被引：2，自引：0，他引：2
叙述了李村河、张村河的自然地理概况和历史沿革,着重分析了2000—2003年李村河、张村河水质污染状况。对调查布设的18个监测断面所获取的数据进行全面系统的分析,特别对以前未布设例行监测站位的大村河、水清沟河的数据进行深入分析和研究,指出这两条河流对李村河水质逐渐恶化应承担责任。通过对河流监测数据的分析,阐明了李村河流域污染状况及其主要污染物来源,为进一步研究确定李村河流域的污染源奠定了基础,并为彻底治理李村河提供了理论和数据依据。 相似文献
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大沽河干流青岛段水环境容量研究 总被引：4，自引：1，他引：4
本文根据大沽河的水流特性和水文、水质实测资料 ,利用 QUAL2 E综合水质模型 ,分析确定了大沽河干流丰水期和平水期的水环境容量。又利用水库水环境容量的计算方法 ,确定了大沽河干流枯水期的水环境容量。大沽河干流水环境容量的确定 ,可用于河流的水质模拟和预测 ,为实施大沽河污染物总量控制提供基础资料 ,为大沽河流域水污染控制的管理和决策提供科学依据 相似文献
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在理论分析的基础上利用根、茎、叶均可量化的植物模型,开展波浪水槽实验。通过改变实验水深、入射波高、植物分布密度等因素,研究不规则波在植物群传播时沿程波高衰减特性,利用快速傅里叶变换对不规则波频谱变化情况进行分析。结果表明,各植物模型消波效果较好,但很少出现植物消波的边界效应,不规则波沿植物群的波高变化情况多数时与Mendez理论曲线不一致,植物群各部分的波能衰减情况并无固定的变化规律。此外,波能衰减集中在谱峰频率处,且入射波高越大,透射波与入射波之间的谱峰值差值越大,但透射波的频谱宽度与入射波相比无明显变化。本研究可为采用近岸植物消波护岸提供一定的理论依据。 相似文献
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The problem of wave propagation and wave damping in a channel with side porous mattresses of arbitrary shape protruding from the walls is studied. The solution was achieved by applying 3-D boundary element method and was employed to study wave field in the channel and to analyze the effect of the geometry of the mattresses and physical and hydraulic properties of porous material on wave damping. The results show that wave damping in the channel strongly depends on wave parameters, especially, on the wave number. Wave reflection and transmission decrease with increasing the wave number. The results also show that the wave field in the channel strongly depends on the geometry of the mattresses as well as on physical and hydraulic properties of porous material used to build these wave dampers. The geometry of the mattresses and physical and hydraulic properties of porous material have a moderate effect on wave reflection and a significant effect on wave transmission. The results show that wave transmission down the channel decreases with increasing the length and thickness of the mattresses. Moreover, wave transmission decreases with increasing the porosity and damping properties of porous media used to build the mattresses. The analysis shows that porous mattresses protruding from the channel walls are very efficient in damping water waves propagating down the channel and may be built in channels to reduce high waves and achieve desired wave conditions. Theoretical results are in reasonable agreement with experimental data. 相似文献
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河口涨潮槽的研究进展 总被引：3，自引：0，他引：3
河口涨潮槽是河口的重要地貌单元。对河口涨潮槽的发育过程与演化规律的研究在理论上可以丰富河口动力地貌的内容，而在实践上对港口和通航等具有重要的意义。文章认为河口涨潮槽不仅指河口涨潮流作用下形成的冲刷槽，还包括涨潮冲刷坑、涨潮冲刷槽和涨湖水道。国内外关于河口涨潮槽研究较为薄弱，研究内容多集中于涨潮槽的几何形态、涨落槽优势流判别和悬沙输移等方面，定性研究较多，缺乏全面而系统的定量研究，尤其缺乏成因机制方面的深入研究和沉积环境的研究。长江口涨潮槽种类较多，具有一定的研究基础，对其进行系统全面的研究具有重要的意义。 相似文献
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This paper presents results from research on the hydraulic loadings of exposed (unsheltered) jetties (open pile piers with decks and beams). The work presented here focuses on results from physical model tests on wave-induced loads on deck and beam elements of exposed jetties and similar structures. These tests investigated the physics of the loading process, and provided new guidance on wave-in-deck loads to be used in design. Wave forces and pressures were measured on a 1:25 scale model of a jetty head with projecting elements. Structure geometry and wave conditions tested were selected after an extensive literature review (summarised in the paper) and consultation with the project steering group. Different configurations were tested to separate 2-d and 3-d effects, and to identify the effects of inundation and of down-standing beams. 相似文献
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《Marine Geology》2005,214(4):339-364
Quantitative geomorphologic analysis of shallowly buried, dendritic channel systems on the New Jersey shelf provides estimates of paleo-hydrologic parameters needed to link channel morphology to the former hydrodynamic setting. These channels, observed in 1–4 kHz deep-towed chirp seismic data, formed presumably as fluvial systems when the shelf was exposed during the Last Glacial Maximum (LGM). The presumed fluvial origin of these channels is supported by their incision into underlying Pleistocene strata, a chaotic seismic fill unit at their bases which may be indicative of non-marine gravel lag, and measured stream junction angles that are consistent with a riverine origin. The channels would also have been subjected to estuarine/tidal environments during ensuing sea-level rise. We employ empirically derived hydraulic equations for modern rivers and estuaries to estimate paleo-discharges, velocities and maximum shear stresses, using the preserved and interpolated paleo-channel geometries as a guide. Generally, trunk/main channels have box-like, symmetric cross-sections, with width/depth ratios of >100, whereas smaller, tributary channels have more v-shaped, asymmetric cross-sections with width/depth ratios of ∼40–70. The high width/depth ratios, along with low sinuosities (∼1.1) and slopes (<0.02°), are consistent with braided streams as specified by a modern river classification system. However, the channels show no evidence of braiding. We hypothesize instead that these channel systems are immature, having had insufficient time to develop high sinuosities that would otherwise be expected before they were drowned by the Holocene transgression. Mean paleo-flow estimates for these systems assuming a tidal environment (1.0–1.5 m/s) are consistent with modern tidal creeks comparable to the sizes of channels observed here (<2 km wide and <25 m deep). Estimated tidal shear stresses would be sufficient to initiate sediment transport of grains 2–8 mm in diameter (coarse sand and fine gravel) as bedload and finer grained material in suspension. However, paleo-flow estimates assuming a fluvial environment (1.1–2.0 m/s) are generally too high for a non-tidal creek, given the presumed low hydraulic gradients in this coastal plain setting. Retrodicted fluvial discharge and boundary shear stresses would have been sufficient to transport particles up to ∼15 mm in diameter (gravel) as bedload; these grain sizes are too coarse to be transported by sluggish coastal plain rivers. We conclude that either flows were quite high when this system was first incised fluvially, perhaps due to meltwater pulses following the LGM, or that tidal influences have modified the original fluvial geometry. 相似文献
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A numerical simulation model is developed to investigate wave profiles and velocities in harbor channels. The Galerkin Technique is coupled with the finite element method in the flow model. An important feature is the addition of terms in the momentum equation to account for the vertical accelerations. The model can be used by ocean engineers to analyze the effects of varying channel geometry on wave oscillations and velocities in a channel connecting a harbor to the ocean. 相似文献
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《中国海洋工程》2015,(5)
A numerical solution was derived to determine wave field in a converging channel bounded by rubble-mound jetties. The solution was achieved by applying boundary element method. The model was applied to analyze the effect of channel convergence, the cross-section of the jetties and their physical and damping properties on wave field in the channel. The study reveals numerous non-intuitive results specific for jetted and convergent channels. The analysis shows that wave reflection is usually low and is of secondary practical importance. Wave transmission strongly depends on the channel geometry and transmitted waves may be higher than incident waves, despite reflection and damping processes. Moreover, wave transmission depends on physical and damping properties of rubble jetties and the results show that wave transmission may increase with the increasing damping properties of jetties, which is a non-intuitive feature of wave fields in jetted channels. The analysis reveals several novel results of practical importance. It is shown that the rubble-mound jetties should be constructed from the material of high porosity, which ensures low transmission. More attention should be devoted to hydraulic properties of porous materials. It is recommended to use the material of moderate damping properties. The material of high damping properties often increases the wave transmission. It is possible, by a selection of rubble-mound material, to obtain lower transmission level for steep waves than for waves of moderate steepness. A series of laboratory experiments were conducted in the wave flume to verify the theoretical results. The comparisons show that theoretical results are in fairly good agreement with experimental data. 相似文献
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Quarter circular breakwater （QCB） is a new-type breakwater developed from senti-circular breakwater （SCB）. The superstructure of QCB is composed of a quarter circular front wall, a horizontal base slab and a vertical rear wall. The width of QCB＇ s base slab is about half that of SCB, which makes QCB suitable to be used on relatively finn soil foundation. The numerical wave flume based on the Reynolds averaged Navier-Stokes equations for impressible viscosity fluid is adopted in this paper to simulate the hydraulic performances of QCB. Since the geometry of both breakwaters is similar and SCB has been studied in depth, the hydraulic performances of QCB are given in comparison with those of SCB. 相似文献