Submarine debris flow impact on pipelines — Part I: Experimental investigation     

Arash Zakeri  Kaare Heg  Farrokh Nadim 《Coastal Engineering》2008,55(12):1209-1218

Estimating the impact forces exerted by a submarine debris flow on a pipeline is a challenge, and there is room for considerably more work to advance the state of the art. To this end, an experimental program was performed to investigate the impact on two pipeline installation scenarios: 1) suspended pipeline and 2) laid-on-seafloor pipeline. The results and observations from the experimental investigation are discussed. The definition of Reynolds number was modified for non-Newtonian fluids and an ad hoc method was developed to estimate the drag force exerted by an impact perpendicular to the pipe axis. The method may be used in prototype situations to estimate the drag force from submarine debris flow impact on pipelines. The experimental program was complemented by Computational Fluid Dynamics (CFD) analyses, the details of which are discussed in the accompanying paper.  相似文献   

Study on Structure of Arched Longitudinal Beams of Deep Water Wharf     

翟秋  鲁子爱  张淑华 《中国海洋工程》2008,22(4):705-711

High-pile and beam-slab quays have been widely used after several years development. They are mature enough to be one of the most important structural types of wharves in China coastal areas. In order to accommodate large tonnage vessels, wharves should be eorrstructed in deep water gradually. However, conventional high-pile and beam-slab structares are hard to meet the requirements of large deep-water wharf. According to arch＇ s stress characteristics, a new type of wharf with catenary arched longitudinal beams is presented in this paper. The new wharf structure can make full use of arch＇s overhead crossing and reinforced concrete compression resistance, improve the interval between transverse bents greatly, and decrease underwater construction quantity. Thus, the construction cost cab be reduced. Take the third phase project of the Yangshan Deep-water Port for example, comparative analysis on catenary arched longitudinal beams and conventional longitudinal beams has been made. The result shows that with the same wharf length and width, the same loads and same longitudinal beam moment, catenary arch structure can improve the interval between bents up to 28 m, decrease the nmnber of piles and underwater construction quantity.  相似文献   

Suppression of Flow Separation Around A Circular Cylinder by Utilizing Lorentz Force   总被引：2，自引：0，他引：2  

张辉  范宝春  陈志华  周本谋 《中国海洋工程》2008,22(1):87-95

Both experimental and numerical investigations on the flow past a cylinder under the influence of Lorentz force （electromagnetic force） were conducted in an electrically low-conducting fluid. The Lorentz force is applied beth locally, wholly and periodically on the surface of the cylinder, and their control effects for flow ,separation were investigated Both experimental and numerical results show that Lorentz force can suppress the flow separation with Lorentz force applied on beth local and whole surface of the cylinder. However, when the periodic and opposite Lorentz force adopted, the cylinder wake cannot be stabilized.  相似文献   

永定新河口通海航道形成水动力泥沙研究     

陈纯  孙连成  张娜 《海岸工程》2010,29(2):10-16

根据规划永定新河河口拟建一条通海航道,利用了该海域的现场实测资料对水动力条件、地质分布、泥沙特性以及淤积等水动力泥沙特征进行了分析,建立了风浪、潮流和泥沙数学模型,对该航道开挖后的年淤积情况进行计算预测。通过与其临近港口的比较,提出了该航道形成可行性依据,为该航道工程的建设提供科学依据。  相似文献   

Investigation of hydraulics transport time scales within the Arvand River estuary,Iran          下载免费PDF全文

Amir Etemad‐Shahidi  Mostafa Pirnia  Hengameh Moshfeghi  Charles Lemckert 《水文研究》2014,28(25):6006-6015

Transport time scales are key parameters for understanding the hydrodynamic and biochemical processes within estuaries. In this study, the flushing and residence times within the Arvand River estuary have been estimated using a two‐dimensional hydrodynamic model called CE‐QUAL‐W2. The model has been calibrated and verified by two different sets of field data and using the k‐ε vertical eddy diffusivity scheme. Flushing time has been estimated using different methods such as the tidal prism and fraction of freshwater methods. Moreover, residence times have been investigated using pulse residence time, estuarine residence time and remnant function approaches. The results have shown that different methods yield different time scales, and freshwater inflow has the greatest impact upon estimation of residence time, whereas tidal circulation hardly contributes to residence time at all. It has also been shown that the neap‐spring circulation and start phase of simulations have negligible effects on the Arvand's time scales. The investigation of bathymetry showed that two sills of the estuary tend to significantly increase residence time. Understanding the applicability of these time scales and their estimation approaches helps us to evaluate the water quality management of estuaries. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Simulating water temperatures and stratification of a pre‐alpine lake with a hydrodynamic model: calibration and sensitivity analysis of climatic input parameters          下载免费PDF全文

Thomas Bueche  Mark Vetter 《水文研究》2014,28(3):1450-1464

We report on the calibration of the one‐dimensional hydrodynamic lake model Dynamic Reservoir Simulation Model to simulate the water temperature conditions of the pre‐alpine Lake Ammersee (southeast Germany) that is a representative of deep and large lakes in this region. Special focus is given to the calibration in order to reproduce the correct thermal distribution and stratification including the time of onset and duration of summer stratification. To ensure the application of the model to investigate the impact of climate change on lakes, an analysis of the model sensitivity under stepwise modification of meteorological input parameters (air temperature, wind speed, precipitation, global radiation, cloud cover, vapour pressure and tributary water temperature) was conducted. The total mean error of the calibration results is ?0.23 °C, the root mean square error amounts to 1.012 °C. All characteristics of the annual stratification cycle were reproduced accurately by the model. Additionally, the simulated deviations for all applied modifications of the input parameters for the sensitivity analysis can be differentiated in the high temporal resolution of monthly values for each specific depth. The smallest applied alteration to each modified input parameter caused a maximum deviation in the simulation results of at least 0.26 °C. The most sensitive reactions of the model can be observed through modifications of the input parameters air temperature and wind speed. Hence, the results show that further investigations at Lake Ammersee, such as coupling the hydrodynamic model with chemo‐dynamic models to assess the impact of changing climate on biochemical conditions within lakes, can be carried out using Dynamic Reservoir Simulation Model. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

波浪滑翔机水下牵引机结构设计与分析     

曹守启  冯江伟 《海洋工程》2020,38(2):92-100

为满足对远洋环境进行长时间、大范围监测的实际需求,设计提出一种波浪动力滑翔机,该设备是一种无需携带能源即可实现自主航行的新型海洋监测平台,其主体结构由水面母船、水下牵引机和柔性缆绳三大部分组成。平台通过即时获取海洋中的波浪能、太阳能、风能作为行走的动力源,克服了传统海洋监测设备在能源供应上存在的短板。为进一步提升水下牵引机对波浪能的利用率,采用Ansys软件中的Fluent模块对水下牵引机进行水动力仿真研究,分析了侧翼板形状、侧翼板工作最大摆动角度以及侧翼板安装分布间距对滑翔机总体行走效率的影响。结果表明:NACA翼型侧翼板具有更好的水动力性能;随着最大摆动角度的增加,水下牵引机的推进效率先增大后减小,最大摆角在20°左右时,推进效果最佳;随着侧翼板分布间距的增大,水下牵引机的推进效率逐渐减小,分布间距在80 mm左右时,推进效果最佳。  相似文献   

基于指数分析法的西安市土地利用变化及驱动力研究   总被引：1，自引：0，他引：1  

霍艳杰  卫海燕  薛亮  李馥利 《国土资源遥感》2009,(2):49-53

基于2000和2007年2期TM遥感影像,利用指数分析法,分别提取出归一化差异建筑指数(NDBI)、修正归一化差异水体指数(MNDWI)和归一化差异植被指数(NDVI)3种指数模型,分别代表西安市的3种最主要的土地利用类型--建筑用地、水体和植被.采用神经网络分类器进行监督分类,借助ERDAS Imagine 9.0、ENVI、ArcGIS 9.2和Matlab等软件平台,计算出西安市土地利用类型的动态转移矩阵,构建了土地利用变化动态度指数模型,定量分析西安市土地利用的时空变化.依据研究区土地利用变化的结果分析,变化的驱动力因子主要是人口增长、经济增长和政策变动.  相似文献   

The response of a gravel‐bed river planform configuration to flow variations and bed reworking: a modelling study          下载免费PDF全文

Gabriel Kaless  Luca Mao  Johnny Moretto  Lorenzo Picco  Mario A. Lenzi 《水文研究》2015,29(17):3812-3828

A 2D depth‐averaged model has been developed for simulating water flow, sediment transport and morphological changes in gravel‐bed rivers. The model was validated with a series of laboratory experiments and then applied to the Nove reach of the Brenta River (Northern Italy) to assess its bed material transport, interpret channel response to a series of intensive flood events (R.I. ≈ 10 years) and provide a possible evolutionary scenario for the medium term. The study reach is 1400 m long with a mean slope of 0.0039 m m^?1. High‐resolution digital terrain models were produced combining LiDAR data with colour bathymetry techniques. Extensive field sedimentological surveys were also conducted for surface and subsurface material. Data were uploaded in the model and the passage of two consecutive high intensity floods was simulated. The model was run under several hypotheses of sediment supply: one considering substantial equilibrium between sediment input and transport capacity, and the others reducing the sediment supply. The sediment supply was then calibrated comparing channel morphological changes as observed in the field and calculated by the model. Annual bed material transport was assessed and compared with other techniques. Low‐frequency floods (R.I. ≈ 1.5 years) are expected to produce negligible changes in the channel while high floods may erode banks rather than further incising the channel bed. Location and distribution of erosion and deposition areas within the Nove reach were predicted with acceptable biases stemming from imperfections of the model and the specified initial, boundary and forcing conditions. A medium‐term evolutionary scenario simulation underlined the different response to and impact of a consecutive sequence of floods. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

煤层气井排采扰动下局部水动力场对排采的动态影响          下载免费PDF全文

张兆民  史国萍  廉永彪 《山东国土资源》2018,34(9)

煤层气主要以吸附态存在于煤层中,其产出需要历经解吸—扩散—渗流的过程。煤层气的产出过程说明,煤岩储层压力低于煤层气的临界解吸压力是煤层气解析产出的关键。排水降压是降低煤岩储层压力最为行之有效的方法,在排水降压的过程中会对地下原始水动力场产生扰动,在井周围形成局部水动力场,从而影响排水降压的效能。该文根据地下水的流动状态、区域构造发育状态,结合煤储层与含水层的组合关系,提出了煤储层排水降压过程可能出现有效扰动型、含水层水入侵型、地表淡水入侵型等3种局部水动力场,并结合实例分析了不同种类水动力场对煤层气排采的动态影响,对指导煤层气的排采具有实际意义。  相似文献