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Hydrodynamic Characteristics of the Continental Intercalaire and Continental Hamadien Aquifer Systems in the Iullemeden Basin of Tahoua Region Republic of Niger 预览
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作者 Abdel Kader Hassane Saley Issoufou Sandao +2 位作者 Jean-Luc Michelot Boureï ma Ousmane 《水资源与保护(英文)》 2019年第9期1188-1205,共18页
This study was conducted in the region of Tahoua the northeastern part of the Southern Illulemeden sedimentary basin. In this region the transboundary aquifer system of Continental Intercalaire (CI) and the Continenta... This study was conducted in the region of Tahoua the northeastern part of the Southern Illulemeden sedimentary basin. In this region the transboundary aquifer system of Continental Intercalaire (CI) and the Continental Hamadien (CH) are potentially rich in underground water especially in free and captive aquifers. More, this water is the main source of drinking water for the populations, the animals and for agriculture and extractive industries. However, the population growth, the agricultural development, and the climate change have a real impact on the dynamics of groundwater and the exploitation of these resources. Hence, this study aims at analyzing the behavior of aquifers and assessing the impact of various natural and anthropogenic factors. Especially it matters to analyze the drilling parameters and cuttings, logging data and pumping test of nine new boreholes. The results reveal that the depths equipped with boreholes catching the CI/CH complex vary from 70 to 800 meters from East to West while the average thickness of the reservoir CH is 50 meters and it mainly consists of coarse sandstone. Drilling penetrated more than 100 meters into the CI without reaching the base. The CI tank is composed of several layers of gravel and clay whilst the CI/CH aquifers flow rates range from 0.2 to 22.8 m3/h/m. So this is cause of great variability of the water potential within this aquifer. Lastly, the transmissivity coefficients are more important in the CH than in the CI, and the water flow average rates range respectively from 29 m/year to 7 m/year. 展开更多
关键词 Iullemeden BASIN CONTINENTAL Intercalaire/Continental Hamadien NIGER Tahoua HYDROGEOLOGY HYDRODYNAMICS
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Dimension-Reduced Model for Deep-Water Waves 预览
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作者 Michael Bestehorn Peder A. Tyvand Thomas Michelitsch 《应用数学与应用物理(英文)》 2019年第1期72-92,共21页
Starting from the 2D Euler equations for an incompressible potential flow, a dimension-reduced model describing deep-water surface waves is derived. Similar to the Shallow-Water case, the z-dependence of the dependent... Starting from the 2D Euler equations for an incompressible potential flow, a dimension-reduced model describing deep-water surface waves is derived. Similar to the Shallow-Water case, the z-dependence of the dependent variables is found explicitly from the Laplace equation and a set of two one- dimensional equations in x for the surface velocity and the surface elevation remains. The model is nonlocal and can be formulated in conservative form, describing waves over an infinitely deep layer. Finally, numerical solutions are presented for several initial conditions. The side-band instability of Stokes waves and stable envelope solitons are obtained in agreement with other work. The conservation of the total energy is checked. 展开更多
关键词 HYDRODYNAMICS OCEAN WAVES DEEP-WATER WAVES Numerical Solutions FRACTAL Derivatives
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空化水动力学非定常特性研究进展及展望 预览 被引量:1
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作者 季斌 程怀玉 +3 位作者 黄彪 罗先武 彭晓星 龙新平 《力学进展》 EI CSCD 北大核心 2019年第1期428-479,共52页
空化作为一种重要的复杂水动力学现象,具有明显的三维流动特征与剧烈的非定常特性,在水力机械、船舶推进器、水利工程中广泛存在,且通常会带来不利的影响,长期以来一直是水动力学领域研究的重点与难点课题之一.本文首先从实验测量和数... 空化作为一种重要的复杂水动力学现象,具有明显的三维流动特征与剧烈的非定常特性,在水力机械、船舶推进器、水利工程中广泛存在,且通常会带来不利的影响,长期以来一直是水动力学领域研究的重点与难点课题之一.本文首先从实验测量和数值模拟两个角度,综述了空化水动力学非定常特性研究的发展概况,分析了当前存在的问题.在空化实验研究中,主要介绍了空化水洞、空化流场测量以及多物理场同步测量等方面所取得的进展.在数值模拟方法中,对目前的空化模型和湍流模型进行了分类介绍,并重点讨论了大涡模拟、验证和确认等在空化流模拟中的应用.之后以附着型空化为主,同时兼顾云状空泡、空蚀、涡空化等,梳理了其研究中存在的几个关键科学问题,包括空化演变、空化流动的三维结构、失稳机制、空化不稳定性及其与低频压力脉动的联系、空化与旋涡的相互作用、空化与弹性水翼的流固耦合、空化对尾流场影响等.最后展望了空化水动力学的研究方向和未来发展趋势. 展开更多
关键词 空化 水动力学 空泡流 附着型空化 空化模型
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Fluent在螺旋桨与舵附推力鳍数值模拟中的应用 预览
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作者 牛振华 殷曼珂 孟伟娜 《舰船科学技术》 北大核心 2019年第8期16-18,共3页
动力系统是船舶的重要组成部分,随着船舶的高速化、大型化发展趋势,对船舶动力系统的性能有更高的要求,在船舶动力系统中,螺旋桨是一种具有复杂作用力的机构,舵附推力鳍是螺旋桨的尾流能量收集装置,对于改善舰船螺旋桨的水动力性能有重... 动力系统是船舶的重要组成部分,随着船舶的高速化、大型化发展趋势,对船舶动力系统的性能有更高的要求,在船舶动力系统中,螺旋桨是一种具有复杂作用力的机构,舵附推力鳍是螺旋桨的尾流能量收集装置,对于改善舰船螺旋桨的水动力性能有重要作用。Fluent是一种计算流体力学CFD的数值模拟软件,广泛应用于各种机械设备如机翼、汽车、风力发电机扇叶等的流体动力学分析。本文首先介绍了Fluent的基本原理,采用面元法建立了螺旋桨的流体动力学模型,并基于Fluent对螺旋桨和舵附推力鳍进行了有限元建模和水动力特性仿真。 展开更多
关键词 螺旋桨 舵附推力鳍 流体动力学 FLUENT
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鱼卵漂流的欧拉-拉格朗日模型与产卵量估算
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作者 余康 陈永灿 +2 位作者 林俊强 朱德军 段辛斌 《水力发电学报》 CSCD 北大核心 2019年第6期56-68,共13页
从河流鱼类早期资源研究和保护的角度,立足鱼卵运动,将传统二维浅水模型与三维粒子追踪结合起来,建立了适用于天然河流鱼卵漂流的欧拉-拉格朗日模型。模型能够模拟对流和紊动扩散作用下鱼卵在河道内的三维运动和散布特性。模型效果通过... 从河流鱼类早期资源研究和保护的角度,立足鱼卵运动,将传统二维浅水模型与三维粒子追踪结合起来,建立了适用于天然河流鱼卵漂流的欧拉-拉格朗日模型。模型能够模拟对流和紊动扩散作用下鱼卵在河道内的三维运动和散布特性。模型效果通过模拟文献中的室内水槽PTV试验,对比实测鱼卵运动特性参数得到了验证。将模型应用于长江中游藕池河支流鱼卵野外示踪漂流试验中,模拟分析了鱼卵在河道内的平面迁移动态、垂向混合规律、断面分布特性以及河道地形和水动力的影响和作用;重点讨论了鱼卵断面浓度分布不均对产漂流性卵鱼类早期资源量(产卵规模)估算的影响,并通过模拟对传统的断面平均估算方法进行了校正,校正效果得到了示踪鱼卵漂流回捕实测数据的良好验证,鱼卵总量估算误差大大降低。此外,模拟还发现鱼卵漂流过程中的平均速度滞后于水流断面平均流速,在产卵场精确定位时须予以考虑。 展开更多
关键词 鱼卵运动 水动力 欧拉-拉格朗日方法 漂流性卵 散布规律 产卵规模估算
Hydrodynamic Characteristics of Xenon Bubbles in a Bubble Column 预览
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作者 Tang Xiaojin 《中国炼油与石油化工:英文版》 SCIE CAS 2019年第3期90-93,共4页
Xenon was used as the gas phase to investigate the hydrodynamic characteristics in a bubble column.It was found that the flow pattern is mainly in the churn-turbulent flow regime through analysing the relationship bet... Xenon was used as the gas phase to investigate the hydrodynamic characteristics in a bubble column.It was found that the flow pattern is mainly in the churn-turbulent flow regime through analysing the relationship between the slip velocity and gas holdup.The influence of operating conditions on the gas holdup and the Sauter mean diameter was studied.The experimental results show that the Sauter mean diameter decreases with the increase of energy dissipation rate.A new correlation was developed to predict the Sauter mean diameter with an average error of less than 15%. 展开更多
关键词 XENON BUBBLE COLUMN HYDRODYNAMICS mean BUBBLE DIAMETER
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Numerical simulation of droplet-formation in rotary atomizer 预览
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作者 Naoki Igari Takuro Iso +2 位作者 Yu Nishio Seiichiro Izawa Yu Fukunishi 《力学快报:英文版》 CAS CSCD 2019年第3期202-205,共4页
Numerical simulations of the liquid flow scattering from rotary atomizers are performed using an incompressible smoothed particle hydrodynamics (SPH) method. The influence of grooves at the edges of the atomizers on t... Numerical simulations of the liquid flow scattering from rotary atomizers are performed using an incompressible smoothed particle hydrodynamics (SPH) method. The influence of grooves at the edges of the atomizers on the formation of ligaments and droplets is investigated changing the numbers and shapes of the grooves. As a result, it is found that small droplets are likely to be generated when the number of grooves is large and the depth of grooves is deep. It is also found that the grooves work more effectively in bell-cup atomizers than in disk type atomizers. 展开更多
关键词 Smoothed particle HYDRODYNAMICS (SPH) ROTARY ATOMIZER GROOVES DROPLET
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基于液体流阻推导的多因素影响下BPR函数改进研究
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作者 戴学臻 成洪博 成为 《电子测量技术》 2019年第12期21-27,共7页
为了探究更符合实际的城市道路交通路阻计算函数,通过将相对拥挤的城市道路中的交通流量(转换成对应当量的机动车流量)产生的交通阻抗类比于流体力学中液体在特定条件下的管道设施中,按照一定规律流动时产生的流动阻力,并以此为基础对... 为了探究更符合实际的城市道路交通路阻计算函数,通过将相对拥挤的城市道路中的交通流量(转换成对应当量的机动车流量)产生的交通阻抗类比于流体力学中液体在特定条件下的管道设施中,按照一定规律流动时产生的流动阻力,并以此为基础对广泛使用的BPR函数进行改进。该函数主要涉及:服务水平、车流密度、车辆组成因素,在此基础上构建出完整函数并通过实际数据标定系数。最后以西安南二环处的交通量实测数据为例分析该函数的准确性与可靠性。结果表明,针对我国城市道路计算道路阻抗时,必须考虑多个因素的影响,改进函数的结果优于BPR函数。 展开更多
关键词 交通流理论 城市交通路段阻抗 流体力学 类比推导
Multi-objective optimization of the kinematic parameters of fish-like swimming using a genetic algorithm method 预览
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作者 Mahdi Abolfazli Esfahani Hamid Reza Karbasian Kyung Chun Kim 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第2期333-344,共12页
This paper investigates the kinematic optimization of fish-like swimming.First,an experiment was performed to detect the motion of the fish tail foil of a fish robot.Next,the kinematic swimming model was verified expe... This paper investigates the kinematic optimization of fish-like swimming.First,an experiment was performed to detect the motion of the fish tail foil of a fish robot.Next,the kinematic swimming model was verified experimentally using an image processing method.The model includes two rotational motions:caudal foil motion and foil-pitching motion.The kinematic model allows us to evaluate the influence of motion trajectory in the optimization process.To optimize the propulsive efficiency and thrust,a multi-objective genetic algorithm was employed to handle with kinematic,hydrodynamic,and propulsion models.The results show that the caudal length has a significant effect on the performance of the flapping foil in fish-like swimming,and its influence on the motion trajectory may increase the propulsive efficiency to as high as 98%in ideal conditions.The maximum thrust coefficient can also reach approximately 3 in ideal conditions. 展开更多
关键词 Fish-like SWIMMING fish robot HYDRODYNAMICS optimization genetic algorithm
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拉坦前列素和毛果芸香碱对DBA/2J小鼠房水动力学及眼压控制作用的研究 预览
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作者 邢超 高常青 +1 位作者 雷苑 孙兴怀 《中国眼耳鼻喉科杂志》 2019年第4期232-235,共4页
目的研究DBA/2J小鼠房水动力学特点及对常用青光眼降眼压药物的反应。方法将实验小鼠按不同月龄(3月龄或10月龄)、不同品系(DBA/2J或C57BL/6)、不同给药药物(0.005%拉坦前列素或0.5%毛果芸香碱),分为8个实验组,8只/组,共128眼。将药物... 目的研究DBA/2J小鼠房水动力学特点及对常用青光眼降眼压药物的反应。方法将实验小鼠按不同月龄(3月龄或10月龄)、不同品系(DBA/2J或C57BL/6)、不同给药药物(0.005%拉坦前列素或0.5%毛果芸香碱),分为8个实验组,8只/组,共128眼。将药物滴于右眼,给药2周;左眼作为自身对照,眼表给予磷酸盐缓冲液。毛果芸香碱每天眼表给药2次(分别在上午9时和下午5时),拉坦前列素每天眼表给药1次(上午9时)。小鼠眼压由Tonolab测量,房水流畅系数采用眼球灌注法测得。结果对于3月龄小鼠,拉坦前列素和毛果芸香碱在C57BL/6和DBA/2J小鼠上降眼压效果良好(眼压下降幅度为13.8%38.9%)。然而,对于10月龄DBA/2J小鼠,毛果芸香碱给药后小鼠眼压与对照眼相比差异无统计学意义(n=8,P>0.05);拉坦前列素的降眼压效果较3月龄DBA/2J小鼠亦有明显下降(5.4mmHgvs.2.6mmHg)。在3月龄和10月龄C57BL/6小鼠上,2种药物的降眼压幅度更为相似。结论DBA/2J小鼠作为青光眼模型,由于其虹膜色素脱离引起小梁网阻塞等特点,并非适合所有降眼压药物的筛选,特别是通过经典通路降眼压的药物。 展开更多
关键词 DBA/2J C57BL/6 拉坦前列素 毛果芸香碱 房水动力学
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舰炮驻退机流场研究 预览
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作者 刘大庆 李翔 邱群先 《舰船科学技术》 北大核心 2019年第15期149-153,共5页
驻退机是舰炮反后坐装置的重要组成部分。驻退机传统的设计计算方法复杂,误差较大,所能收集的数据有限,无法得到整体流场的情况。某舰炮在长连发射击试验时,出现复进时间长的故障。对该问题传统设计方法计算与射击试验结果不符。本文采... 驻退机是舰炮反后坐装置的重要组成部分。驻退机传统的设计计算方法复杂,误差较大,所能收集的数据有限,无法得到整体流场的情况。某舰炮在长连发射击试验时,出现复进时间长的故障。对该问题传统设计方法计算与射击试验结果不符。本文采用计算流体力学方法对驻退机流场重新进行分析,通过计算机模拟仿真,研究驻退机内部流场的变化规律,利用流体力学相关理论解决实际工程问题,为解决复进时间长问题提供参考。 展开更多
关键词 驻退机 动网格 多相流 流体力学
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Development of naoe-FOAM-SJTU solver based on OpenFOAM for marine hydrodynamics 预览
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作者 Jian-hua Wang Wei-wen Zhao De-cheng Wan 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第1期1-20,共20页
A CFD solver naoe-FOAM-SJTU (The abbreviation naoe stands for naval architecture and ocean engineering) is developed based on the open source platform OpenFOAM with the purpose of simulating various marine hydrodynami... A CFD solver naoe-FOAM-SJTU (The abbreviation naoe stands for naval architecture and ocean engineering) is developed based on the open source platform OpenFOAM with the purpose of simulating various marine hydrodynamic problems.In the present paper,self-developed modules,i.e.,wave generation and absorption,6 degrees of freedom motion,mooring system,dynamic overset grid,fluid-structure interaction,unsteady actuator line model,implemented on the open source platform OpenFOAM are introduced to illustrate the development of the marine hydrodynamics CFD solver.Furthermore,extensive simulations of marine hydrodynamic problems using the developed modules are conducted and validated by available experimental data.It has been proved that the CFD solver naoe-FOAM-SJTU is suitable and reliable in predicting the complex viscous flow around ship and offshore structures.Efficiency and accuracy need to be focused in the future development of the present CFD solver. 展开更多
关键词 MARINE HYDRODYNAMICS fluid-structure INTERACTION overset GRID naoe-FOAM-SJTU SOLVER OPENFOAM
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Application of Regional Ocean Modeling System for Hydrodynamics in Binh Cang-Nha Trang Bay, Vietnam 预览
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作者 Pham Xuan Duong Phan Minh-Thu Bui Hong Long 《海洋科学杂志(英文)》 2019年第1期1-6,共6页
Based on the data collected at the Cau Da station, the Regional Ocean Modeling System (ROMS) is applied for hydrodynamics (e.g. circulation and temperature-salinity) in Binh Cang - Nha Trang Bay, Vietnam. The results ... Based on the data collected at the Cau Da station, the Regional Ocean Modeling System (ROMS) is applied for hydrodynamics (e.g. circulation and temperature-salinity) in Binh Cang - Nha Trang Bay, Vietnam. The results present the several cases of hydrodynamic regimes in the Bay during two mainly monsoon seasons (northeast and southwest monsoons). The clearly hydrodynamic regime occurs in the bay due to the impacts of rivers and monsoon conditions. These changes could be contributed to the hydrodynamic systems and water exchanges, that support basic scientific information for sustainable development of Binh Cang - Nha Trang bay. 展开更多
关键词 ROMS Binh Cang Nha Trang BAY HYDRODYNAMICS
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基于个体化逆向工程和双向流固耦合模型的B型主动脉夹层数值模拟血流分析
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作者 张韬 郭红斌 +4 位作者 李伟浩 李伟 张学民 李清乐 张小明 《中华医学杂志》 CAS CSCD 北大核心 2019年第2期142-147,共6页
目的建立基于个体化逆向工程和双向流固耦合模型的B型主动脉夹层数值模拟模型,探讨计算流体力学技术在主动脉夹层重塑研究中的应用价值。方法获取北京大学人民医院血管外科B型主动脉夹层患者手术前、第一破口封堵后1周、第一破口封堵后... 目的建立基于个体化逆向工程和双向流固耦合模型的B型主动脉夹层数值模拟模型,探讨计算流体力学技术在主动脉夹层重塑研究中的应用价值。方法获取北京大学人民医院血管外科B型主动脉夹层患者手术前、第一破口封堵后1周、第一破口封堵后6年和远端破口封堵后3个月的4次CT检查资料,使用Mimics逆向工程重建主动脉夹层三维模型,经Geomagic平滑化后运用ANSYS流体力学模块构建基于双向流固耦合模型进行主动脉夹层血流动力学数值模拟。分析血流动力学参数与主动脉夹层重塑之间的关系。结果成功建立基于个体化逆向工程和双向流固耦合模型的B型主动脉夹层数值模拟模型。主动脉弓远段与胸降主动脉连接处大弯侧存在血流压强峰值区。主动脉夹层假腔的壁应力远高于真腔,壁应力峰值分布在假腔的边缘处及破口附近。成功封堵第一破口后,夹层假腔流线明显减少,剩余腹主动脉下段残余假腔血流自左髂总动脉破口逆行向上灌注,并于假腔顶部形成涡流,有利于夹层血栓化重塑。第二破口位置残留假腔压力持续高于真腔,与动脉瘤形成相关。结论基于逆向工程个体化设计的双向流固耦合主动脉夹层数值模拟模型能够揭示B型主动脉夹层相对真实的血流动力和管壁应力特征。 展开更多
关键词 流体力学 动脉瘤 夹层 逆向工程 流固耦合
Turbulence and suspended sediment processes in the Garonne Rivertidal bore in November 2016 预览
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作者 David Reungoat Xinqian Leng Hubert Chanson 《国际泥沙研究:英文版》 SCIE 2019年第5期496-508,共13页
A tidal bore is a water discontinuity at the leading edge of a ood tide wave in estuaries with a large tidal range and funneling topography. New measurements were done in the Garonne River tidal bore on 14 15 November... A tidal bore is a water discontinuity at the leading edge of a ood tide wave in estuaries with a large tidal range and funneling topography. New measurements were done in the Garonne River tidal bore on 14 15 November 2016, at a site previously investigated between 2010 and 2015. The data focused on long, continuous, high-frequency records of instantaneous velocity and suspended sediment con- centration (SSC) estimate for several hours during the late ebb, tidal bore passage and ood tide. The bore passage drastically modi ed the ow eld, with very intense turbulent and sediment mixing. This was evidenced with large and rapid uctuations of both velocity and Reynolds stress, as well as large SSCs during the ood tide. Granulometry data indicated larger grain sizes of suspended sediment in water samples compared to sediment bed material, with a broader distribution, shortly after the tidal bore. The tidal bore induced a sudden suspended sediment ux reversal and a large increase in suspended sedi- ment ux magnitude. The time-variations of turbulent velocity and suspended sediment properties indicated large uctuations throughout the entire data set. The ratio of integral time scales of SSC to velocity in the x-direction was on average TE,SSC/TE,x 0.16 during the late ebb tide, compared to TE,SSC/ TE,x 0.09 during the late ood tide. The results imply different time scales between turbulent velocities and suspended sediment concentrations. 展开更多
关键词 TIDAL BORE Garonne RIVER HYDRODYNAMICS Suspended SEDIMENT Field observations Turbulence-sediment suspension interactions
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Numerical simulation of hydrodynamic environment effects of the reclamation project of Nanhui tidal flat in Yangtze Estuary 预览
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作者 Di-fan Cao Yong-ming Shen +1 位作者 Mei-rong Su Chun-xue Yu 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第3期603-613,共11页
The reclamation is the main method in the coast exploitation, and the assessment of the hydrodynamic environment effect of the reclamation project is important for project's site selection and environmental protec... The reclamation is the main method in the coast exploitation, and the assessment of the hydrodynamic environment effect of the reclamation project is important for project's site selection and environmental protection. With consideration of the baroclinic water, a 3?D numerical model MIKE3 is applied to simulate Yangtze Estuary's hydrodynamic environment to predict the impacts of the reclamation project of the Nanhui tidal flat. The simulated results of the model agree well with the field data of the tide level, the current speed, the current direction, the temperature, the salinity and the water quality, and it is indicated that after the reclamation project, the high tide level will be lower, while the low tide level will be higher in the South Branch in general. During the spring tide in the dry season, the peak velocity during the ebb tide in the North Channel will be reduced by 13%, while it will be increased by 21% in the South Channel in average. The salinity will be increased in the North Channel, while reduced in the South Passage, besides, the reclamation project will aggravate the saltwater intrusion of the North Branch. The value of N/P will be increased by about 4% in the whole South Branch except for the North Channel, leading to a slight aggravation of the phosphorus restriction effect in the Yangtze Estuary. 展开更多
关键词 YANGTZE ESTUARY 3-D numerical model HYDRODYNAMICS NUTRIENTS RECLAMATION project
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An improved predictive-corrective incompressible smoothed particle hydrodynamics method for fluid flow modelling 预览
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作者 Chong Peng Christoph Bauinger +2 位作者 Kamil Szewc Wei Wu Hui Cao 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第4期654-668,共15页
Predictive-corrective incompressible smoothed particle hydrodynamics (PCISPH) is an efficient SPH variation originally developed for computer graphics. Its application in modeling physics-focused fluid flows has not y... Predictive-corrective incompressible smoothed particle hydrodynamics (PCISPH) is an efficient SPH variation originally developed for computer graphics. Its application in modeling physics-focused fluid flows has not yet been reported. In this work, an improved PCISPH method is presented for physics-focused fluid flow modeling. Different from traditional weakly-compressible SPH (WCSPH) and incompressible SPH (ISPH), PCISPH satisfies the incompressibility requirement at the particle level without a predefined equation of state. The pressure is obtained using an iterative predictive-corrective scheme at each individual particle. The presented PCISPH allows much larger time steps compared with WCSPH. It also avoids the time-consuming solution of Pressure Poisson Equation (PPE) in ISPH. Consequently, the PCISPH has high computational efficiency even with millions of computational particles. To ensure physically correct modeling of fluid flows, we employ several techniques to enhance the accuracy and stability of the PCISPH:(1) the continuity equation is used to predict density, replacing the mass summation approach used in the original PCISPH,(2) numerical diffusion and pressure smoothing are introduced to improve the pressure computation,(3) a generalized boundary treatment approach which can handle arbitrarily complex geometries is employed,(4) an adaptive time-stepping algorithm is used, allowing efficient simulation as well as ensuring stability. The performance of the improved PCISPH is systematically investigated using three standard SPH validation cases. Comparisons between the improved PCISPH and the state-of-the-art 5 - SPH are presented. It is found that the improved PCISPH gives numerical results as accurate as J - SPH, except for having moderate temporal pressure oscillations. However, the numerical results show that the improved PCISPH is approximately five times faster than 8 -SPH. The improved PCISPH method shows to be a promising tool for large-scale three-dimensional fluid flow modeling. 展开更多
关键词 Smoothed particle HYDRODYNAMICS INCOMPRESSIBILITY predictive-corrective scheme high efficiency
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Sediment Transport Capacity Under the River-Tide Interaction in the Changjiang Estuary 预览
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作者 FENG Zhi-yong TAN Guang-ming XIA Jun-qiang 《中国海洋工程:英文版》 SCIE EI CSCD 2019年第2期207-218,共12页
Sediment transport capacity is a fundamental parameter in sediment transport theory and its accurate calculation is important from both theoretical and engineering viewpoints. The capacity of sediment transport has be... Sediment transport capacity is a fundamental parameter in sediment transport theory and its accurate calculation is important from both theoretical and engineering viewpoints. The capacity of sediment transport has been studied extensively by many researchers in the last decades. Nevertheless, the underlying mechanism behind sediment transport capacity in estuaries remains poorly understood. The current study aims to explore the impact of the river–tide interaction on sediment transport and establish a formula of sediment transport capacity under the river–tide interaction. The impact of the river–tide interaction on the hydrodynamics and sediment dynamics in the Changjiang Estuary was analyzed, a practical method for describing the variation in tide-runoff ratio was established, and a formula of sediment transport capacity considering the impact of river–tide interaction was proposed by introducing the tide-runoff ratio. The new method bridged the gap between two well-known sediment transport capacity methods by considering the variation in the index a for the gravitational term and overcomes the drawback of distinguishing flood/dry season or spring/ebb tide in the calculation of estuarine sediment transport. A large amount of flow and sediment data obtained from the Changjiang Estuary were collected to verify the proposed formula. The effect of salt-fresh water mixture and the morphological evolution on sediment transport capacity of the Changjiang Estuary were discussed. 展开更多
关键词 SEDIMENT transport capacity RIVER TIDE INTERACTION hydrodynamics and SEDIMENT dynamics Changjiang ESTUARY (Yangtze Estuary)
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Chiari畸形I型的颅颈交界区脑脊液流体力学分型及其手术策略
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作者 范涛 吴锟 +3 位作者 赵新岗 梁聪 徐滨 王寅千 《中华神经外科杂志》 CSCD 北大核心 2019年第8期823-828,共6页
目的分析Chiari畸形I型的颅颈交界区脑脊液流体力学分型、手术策略及其疗效。方法回顾性纳入2008年1月至2015年12月首都医科大学三博脑科医院脊髓脊柱中心收治的126例Chiari畸形I型患者,术前均行颅颈交界区MRI扫描,根据脑脊液流动异常... 目的分析Chiari畸形I型的颅颈交界区脑脊液流体力学分型、手术策略及其疗效。方法回顾性纳入2008年1月至2015年12月首都医科大学三博脑科医院脊髓脊柱中心收治的126例Chiari畸形I型患者,术前均行颅颈交界区MRI扫描,根据脑脊液流动异常的位置将其分为I型(36例)、II型(48例)及HI型(42例)。术中超声再次探査脑脊液情况决定手术策略,1型患者中,34例采用硬膜下减压术,余2例采用蛛网膜下减压术;U型患者中,36例采用蛛网膜下减压术,余12例采用硬膜下减压术;ID型患者中,40例采用蛛网膜下减压术,余2例采用硬膜下减压术。术后2周,对患者行影像学复査和改良日本骨科协会(mJOA)颈椎评分。对所有患者行临床随访,采用mJOA颈椎评分表评估脊髓空洞相关症状的改善情况,采用芝加哥Chiari成果量表(CCOS)评估术后神经功能恢复情况。结果126例患者的手术均成功。术后无一例出现新发神经功能缺损症状,8例(6.3%)发热,5例(4.0%)发生脑脊液漏,对症治疗后均好转。术后2周,影像学复査显示2例患者(皿型,行蛛网膜下减压术)的脊髓空洞未见明显改善,进一步行脊髓空洞-胸腔分流术后症状改善;126例患者的rnJOA颈椎评分较术前提高[分别为(12.7±2.0)分、(10.7 ±1.6)分,P <0.01]。126例患者的随访时间为(24. 8 ±8.9)个月(12~96个月)。至末次随访,126例患者的mJOA颈椎评分较术前显著提高[(12.8 ± 1.9)分、(10. 7 土1.6)分,P v 0.01 ],但与术后2周间的差异无统计学意义(P = 0.48);CCOS评分与术后2周的差异也无统计学意义[分别为(14.7±1.5)分、(14.4±1.5)分,P=0.576]。结论根据颅颈交界区脑脊液动力学异常将Chiari畸形I型分为3型,1型主要采用硬膜下减压,皿型主要采用蛛网膜下减压型根据减压骨窗的术中超声探查结果判断如何选择减压方式,术后疗效均较好。 展开更多
关键词 ARNOLD-CHIARI畸形 流体力学 神经外科手术 治疗结果 脑脊液 分型
Dynamic hydraulic jump and retrograde sedimentation in an open channel induced by sediment supply: experimental study and SPH simulation
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作者 ZHENG Xiao-gang CHEN Ri-dong +2 位作者 LUO Min KAZEMI Ehsan LIU Xing-nian 《山地科学学报:英文版》 SCIE CSCD 2019年第8期1913-1927,共15页
Mountainous torrents often carry large amounts of loose materials into the rivers, thus causing strong sediment transport. Experimentally it was found for the first time that when the intensive sediment motion occurs ... Mountainous torrents often carry large amounts of loose materials into the rivers, thus causing strong sediment transport. Experimentally it was found for the first time that when the intensive sediment motion occurs downstream over a gentle slope, the siltation of the riverbed is induced and the sediment particles can move upstream rapidly in the form of a retrograde sand wave, resulting in a higher water level along the river. To further study the complex mechanisms of this problem, a sediment mass model in the framework of the Smoothed Particle Hydrodynamics(SPH) method was presented to simulate the riverbed evolution, sediment particle motion, and the generation and development of dynamic hydraulic jump under the condition of sufficient sediment supply over a steep slope with varying angles. Because the sediment is not a continuous medium, the marker particle tracking approach was proposed to represent a piece of sediment with a marked sediment particle. The twophase SPH model realizes the interaction between the sediment and fluid by moving the bed boundary particles up and down, so it can reasonably treat the fluid-sediment interfaces with high CPU efficiency. The critical triggering condition of sediment motion, the propagation of the hydraulic jump and the initial siltation position were all systematically studied. The experimental and numerical results revealed the extra disastrous sediment effect in a mountainous flood. The findings will be useful references to the disaster prevention and mitigation in mountainous rivers. 展开更多
关键词 DYNAMIC hydraulic jump RETROGRADE SEDIMENTATION SEDIMENT supply Mountainous river Smoothed PARTICLE Hydrodynamics MARKED SEDIMENT PARTICLE
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