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近壁圆柱绕流水动力特性数值模拟与实验研究 总被引:3,自引:0,他引:3
通过数值模拟和物理模型实验,对距壁面一定高度的圆柱绕流水动力特性进行了研究。数值模拟采用有限体积法对标准k-ε模式方程进行离散,采用SIMPLE算法进行求解,模拟绕流流场。在物理模型实验中,将PVC圆管制作的实验模型安放在水槽内,在圆管的跨中沿表面周向均匀布置水下压力传感器,用于测量绕流圆柱体表面动水压力分布。通过改变Re数和间隙比来分析它们对近壁圆柱绕流水动力特性的影响。基于数值流动显示技术,给出了近壁绕流流场的尾流流态分析。通过数值结果与实验结果的对比,对近壁绕流圆柱体的升力系数及其表面动水压力分布进行了研究,对比结果显示了较好的一致性。 相似文献
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波浪对海底管线作用的物理模型实验及数值模拟研究 总被引:7,自引:0,他引:7
利用物理模型实验,测量了海底管线在波浪作用下的水平力和升力,并应用Morison方程及流函数理论,按最小二乘原理得出CD和CM以及CL,讨论了它们与KC,Re之间隙比e/D的关系。本文带应用边界拟合坐标及二维流场的大涡模拟法,模拟了与实验相同工况下海底管线的受力及流场情况,并把物理模型实验和数值模拟的结果进行了比较。 相似文献
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近壁圆柱绕流问题在海底悬跨管道的研究中具有重要的意义。在绕流阻力、升力以及海底土壤的耦合作用下,海底管道所发生的移位、悬跨等现象对于海底管道的安全运行构成了很大的威胁。正确预测各种绕流条件下管流之间的作用力是保证油气管道安全的首要任务。海底管道在极端海洋环境条件下的管、流相互作用为高雷诺数绕流问题,处于高雷诺数下的绕流模拟比处于低雷诺数下的绕流模拟要复杂很多,它需要更精细的网格以及合适的湍流模型。此文对处于悬跨状态下的海底管道进行数值研究,给出不同间隙比下海流绕流海底管道的流场结构形态,分析了间隙比对绕流阻力和绕流升力的影响,为进一步研究海底悬跨管道的受力和变形提供载荷边界数据。 相似文献
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海底对系缆运动及张力影响研究 总被引:1,自引:0,他引:1
对系缆运动及张力进行分析,并考虑海底对系缆的影响。采用细长弹性杆单元模拟系缆微段,建立系缆运动控制方程,采用有限元法对其进行离散,将海底弹性和阻尼作用力添加到离散控制方程中。利用牛顿法和Newmark-β法对离散后的系缆非线性运动方程组进行数值求解。模拟长600 m的系缆顶端受到垂向正弦激励时的运动,分别求得考虑和不考虑海底作用时系缆运动响应和动态张力。通过对比系缆的运动、速度和动态张力结果,发现海底的弹性阻尼作用对系缆的运动及张力特性有极大影响。上述研究工作为计算海底对系缆的作用力提供了新方法。 相似文献
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根据Hamilton变分原理以及Euler-Bernoulli梁理论,推导出两端简支输液直管的自激振动微分方程,与传统的Housner方程相比,该方程增加了管内流体流速时变引起。的耦合力项,因而可用于分析内流流速时变情况下输液管线的动力特性。使用Hermite插值函数和Galerkin法对该微分方程进行离散,得到其有限元形式的表达式。运用该数学模型,通过数值算例,分析了内流流速时变输液直管的动力特性,得出了相应结论。 相似文献
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The forces and moments acting on an oscillating plate at inflow angles at or below stall are well understood. However, there is a shortage of data on surface-piercing plates undergoing rotational oscillation. A set of experiments was conducted on a series of flat plates undergoing forced rotational oscillation in calm water. The impetus for the experiments was an investigation into the hydrodynamics of sailing yacht keels, but the results may be of value for a wide range of engineering problems. The experiments showed that the two-dimensional case was not representative of three-dimensional flow conditions. There was a possible region of transitional flow for the plate in two-dimensional flow, not evidenced in the results for three-dimensional flow. The total roll moment, roll inertia, roll drag and sway force coefficients showed an inverse square root relationship to aspect ratio, with a very weak dependency on oscillation frequency and angle amplitude. Under-plate clearance effects were small for the clearance values investigated. 相似文献
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首次将PIV技术应用于测试偏心环空幂律流体紊流螺旋流速度场,设计了一套可调偏心度的垂直环空管道实验装置。实验为不同浓度的聚丙烯酰胺水溶液在偏心度分别为40%和80%的垂直环空管道内做螺旋流动的PIV实验。得到了轴向速度影响规律:压力梯度一定时,黏滞性的减小或内管转速的增加将使轴向速度增大;流量一定时,黏滞性的减小或内管转速的增加都将使宽间隙处紊流核心区的轴向速度减小;偏心度的增大可以使紊流核心区轴向速度减小;当其它条件相同时,轴向速度随着压力梯度或流量的增加而增大。PIV实验结果与PHOENICS数模结果吻合良好。证明了PIV技术对幂律流体偏心环空螺旋流速度场进行测试是可行的、有效的。 相似文献
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本文用ECMWF2.5×2.5网格点资料通过一个例子,对有利于南海热带气旋发展的环流场作了详细的分析,发现几点事实:(1)扰动在风的垂直切变较大的环境中仍可发展。(2)扰动位于中、低空西南急流左侧,高空南支东风急流右侧时,有利发展。(3)中,低空西南急流形成了扰动环流的强风潮,强风潮从扰动南侧入角,并包围扰动的东半圆。(4)扰动中、低层的入流和高层的外流呈现严重的不对称性。(5)当扰动发展到一定强度时,对南海热带季风环流圈的加强起到正反馈作用。 相似文献
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气井产能的评价,理论基础已相当成熟,实际生产中也已形成相当成熟的方法,具体的操作过程亦不复杂。然而在实际运用中由于受到资料数量和质量的制约,稍不留意就会使得评价结果与实际产能出现较大差异,从而影响开发技术政策的制定、气田的开发效果及气田的经济效益。笔者引入比产能方法,在对XXX气田进行产能评价过程中,遇到一系列难以用常规方法解决的问题,由此引发产能评价的思考,对其原因以及对实际气田开发的影响进行分析和探讨,并提出了相应的应对措施。 相似文献
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船体尾流场测试试验的若干关键技术研究 总被引:1,自引:0,他引:1
根据带不同尾部特征的水滴形船体模型水下伴流场的测量试验情况,对测试系统的几个关键技术进行了较详细的探讨。通过分析研究表明:水下测量试验系统的稳定性好,功能齐全且自动化程度高,在试验研究中有必要对测试技术方面的若干关键环节加以注意,以保证测试的准确性和精度。 相似文献
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在海洋流场数值计算中,当流场中建筑物尺度相对平面网格步长太小时,计算中难以引进其作用,在所得计算结果中难以反映其影响。本文依据流量连续、能量守恒规律,通过水力学物模实验,求得建筑物存在情况下的谢才系数C,解决了计算中的难题。 相似文献
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Zai-Jin You 《Ocean Engineering》1998,26(3):277-285
A simple model is developed to study the inception of sheet flow in oscillatory flow based on the available experimental data. The inception of sheet flow in oscillatory flow is well defined by the simple model: A/d=KA2ω/ν+B, where A is the semi-excursion of wave orbital motion near the bed, d is the grain size, ω is the angular frequency, ν is the kinematic viscosity of water, and K and B are the coefficients and dependent on sediment properties only. The inception velocity of sheet flow derived from the model is shown to be the function of grain size d, oscillatory period T and specific sediment density s. For a given sediment, the inception velocity is found to increase sharply initially with T and then approach a constant at T>6.0 s. The present model is quite simple and gives good agreement with the available experimental data. 相似文献
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Peter Haughton Christopher Davis William McCaffrey Simon Barker 《Marine and Petroleum Geology》2009,26(10):1900-1918
The deposits of subaqueous sediment gravity flows can show evidence for abrupt and/or progressive changes in flow behaviour making them hard to ascribe to a single flow type (e.g. turbidity currents, debris flows). Those showing evidence for transformation from poorly cohesive and essentially turbulent flows to increasingly cohesive deposition with suppressed turbulence ‘at a point’ are particularly common. They are here grouped as hybrid sediment gravity flow deposits and are recognised as key components in the lateral and distal reaches of many deep-water fan and basin plain sheet systems. Hybrid event beds contain up to five internal divisions: argillaceous and commonly mud clast-bearing sandstones (linked debrite, H3) overlie either banded sandstones (transitional flow deposits, H2) and/or structureless sandstones (high-density turbidity currents, H1), recording longitudinal and/or lateral heterogeneity in flow structure and the development of turbulent, transitional and laminar flow behaviour in different parts of the same flow. Many hybrid event beds are capped by a relatively thin, well-structured and graded sand–mud couplet (trailing low-density turbulent cloud H4 and mud suspension fallout H5). Progressive bed aggradation results in the deposits of the different flow components stacked vertically in the final bed. Variable vertical bed character is related to the style of up-dip flow transformations, the distance over which the flows can evolve and partition into rheological distinct sections, the extent to which different flow components mutually interact, and the rate at which the flows decelerate, reflecting position (lateral versus distal) and gradient changes. Hybrid beds may inherit their structure from the original failure, with turbidity currents outpacing debris flows from which they formed via partial flow transformation. Alternatively, they may form where sand-bearing turbidity currents erode sufficient substrate to force transformation of a section of the current to form a linked debris flow. The incorporation of mud clasts, their segregation in near-bed layers and their disintegration to produce clays that can dampen turbulence are inferred to be key steps in the generation of many hybrid flow deposits. The occurrence of such beds may therefore identify the presence of non-equilibrium slopes up-dip that were steep enough to promote significant flow incision. Where hybrid event beds dominate the entire distal fan stratigraphy, this implies either the system was continually out of grade in order to freight the flows with mud clasts and clays, or the failure mechanism and transport path repeatedly allowed transmission of components of the initial slumps distally. Where hybrid beds are restricted to sections representing fan initiation, or occur more sporadically within the fan deposits, this could indicate shorter episodes of disequilibrium, due to an initial phase of slope re-adjustment, or intermittent tectonically or gravity-driven surface deformation or supply variations. Alternatively, changes between conventional and hybrid event beds may record changes in the flow generation mechanism through time. Thus the vertical distribution of hybrid event beds may be diagnostic of the wider evolution of the fan systems that host them. 相似文献
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In the last decade, offshore pipeline engineering extended its action field to very deep waters and continental slopes. This implied the necessity to deal with continental slope instability and mass gravity flows. Mass gravity flows are rare and have random occurrence; therefore, considering also the technical difficulties, the direct measurement of the phenomena is practically impossible. This has encouraged the development of physical and numerical models for investigating the characteristics and intensity of the phenomena (Proc. OTC Conf., Houston, TX (2000); Proc. 19th OMAE Conference, New Orleans, LA (2000)). In order to provide design activities with reliable predictive tools, two numerical models, one for debris flows and the other for turbidity currents, have been developed. The two models are coupled by the bottom boundary conditions of the turbidity current model that depends on the instantaneous velocity of the debris flow model. The two models used together provide a tool for the evaluation of a mass gravity flow event starting as a debris flow and evolving into a turbidity current. 相似文献
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长江口浑浊带核心区北槽水动力特征研究 总被引:4,自引:2,他引:2
本文根据2015年长江口洪季浑浊带水域座底三脚架全水深范围观测数据,对北槽中下段纵横向流、余流结构、边界层特征等进行了深入研究,结果显示:(1)大潮潮流矢量特征在垂向上的变化差异最为显著;北槽中下段水流出现明显的横向输移,指向航槽北面;(2)横向流速在大潮期间的变化(垂线平均)为-0.10~0.39 m/s,小潮期间的变化为-0.13~0.25 m/s;横向平流对于北槽纵向物质输运有显著调整作用;(3)余流垂向差异大,底部几乎为0,小潮期间余流更强;周期性再悬浮的细颗粒泥沙可作为北槽最大浑浊带的重要物质来源;(4)传统六点对数流速拟合法获得摩阻流速误差较大,近底1 m区域高分辨流速剖面是准确获取底边界层参数的有效途径。 相似文献