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Equilibrium Energy and Entropy of Vortex Filaments in the Context of Tornadogenesis and Tornadic Flows
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作者 Pavel Bělík Douglas P. Dokken +3 位作者 Mikhail M. Shvartsman Eric Bibelnieks Robert Laskowski Alek Lukanen 《Open Journal of Fluid Dynamics》 2023年第3期144-176,共33页
In this work, we study approximations of supercritical or suction vortices in tornadic flows and their contribution to tornadogenesis and tornado maintenance using self-avoiding walks on a cubic lattice. We extend the... In this work, we study approximations of supercritical or suction vortices in tornadic flows and their contribution to tornadogenesis and tornado maintenance using self-avoiding walks on a cubic lattice. We extend the previous work on turbulence by A. Chorin and collaborators to approximate the statistical equilibrium quantities of vortex filaments on a cubic lattice when both an energy and a statistical temperature are involved. Our results confirm that supercritical (smooth, “straight”) vortices have the highest average energy and correspond to negative temperatures in this model. The lowest-energy configurations are folded up and “balled up” to a great extent. The results support A. Chorin’s findings that, in the context of supercritical vortices in a tornadic flow, when such high-energy vortices stretch, they need to fold and transfer energy to the surrounding flow, contributing to tornado maintenance or leading to its genesis. The computations are performed using a Markov Chain Monte Carlo approach with a simple sampling algorithm using local transformations that allow the results to be reliable over a wide range of statistical temperatures, unlike the originally used pivot algorithm that only performs well near infinite temperatures. Efficient ways to compute entropy are discussed and show that a system with supercritical vortices will increase entropy by having these vortices fold and transfer their energy to the surrounding flow. 展开更多
关键词 Tornadogenesis Supercritical Vortices vortex filaments Negative Temperature Kinetic Energy ENTROPY Statistical Mechanics Equilibrium Statistics Self-Avoiding Walks Cubic Lattice Monte-Carlo Techniques Pivot Algorithm
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On the Dynamics of Vortex Filaments and Their Core Structure
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作者 Ting Lu (Courant Institute of Mathematical Sciences, New York University) 《Advances in Manufacturing》 SCIE CAS 1999年第2期3-10,共8页
We give a brief review of the asymptotic theory of slender vortex filaments with emphases on (i) the choices of scalings and small parameters characterizing the physical problem,(ii) the key steps in the formulation o... We give a brief review of the asymptotic theory of slender vortex filaments with emphases on (i) the choices of scalings and small parameters characterizing the physical problem,(ii) the key steps in the formulation of the theory and (iii) the assumptions and/or restrictions on the theory of Callegari and Ting (1978).We present highlights of an extension of the 1978 asymptotic theory:the analyses for core structures with axial variation.Making use of the physical insights gained from the analyses,we present a new derivation of the evolution equations for the core structure.The new one is simpler and straightforward and shows the physics clearly. 展开更多
关键词 vortex filaments core structure dynamics asymptotic theory
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Analytical Solutions to the Flow Field Induced by Uniformly Moving Multiple Helical Vortex Filaments
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作者 刘翔 黄其柏 +1 位作者 廖道训 温国珍 《China Ocean Engineering》 SCIE EI 2005年第1期83-96,共14页
This paper presents analytic solutions for the flow field of inviscid fluid induced by uniformly and rigidly moving multiple helical vortex filaments in a cylindrical pipe. The relative coordinate system is set on the... This paper presents analytic solutions for the flow field of inviscid fluid induced by uniformly and rigidly moving multiple helical vortex filaments in a cylindrical pipe. The relative coordinate system is set on the moving vortex filaments. The analytical solutions of the flow field are obtained on the assumption that the relative velocity field induced is time-independent and helically symmetrical. If the radius of the cylindrical pipe approaches infinity, these solutions are also available for unbounded space. The results show that both the absolute velocity field and pressure field are periodical in time, and may reduce to time-independent when the helical vortex filaments are immobile or slip along the filaments themselves. Furthermore, the solution of velocity field is reduced to Okulov's formula for the case of a single static vortex filament in a cylindrical pipe. The calculated locations of pressure peak and valley on the pipe wall agree with experimental results. 展开更多
关键词 multiple helix moving vortex filaments swirling flow
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随时间发展的三维混合层流场的研究 被引量:1
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作者 沈利平 林建忠 傅斌 《力学学报》 EI CSCD 北大核心 1996年第1期1-7,共7页
构造了三维混合层流场用离散涡丝描述的计算模型并进行了数值模拟.给出了流场的涡结构以及不同剪切率、不同扰劝强度下涡结构的特征,得到了流场中的平均速度、动量厚度.由计算被动粒子显示了流场螺旋涡结构的图像.做了相应的流动显... 构造了三维混合层流场用离散涡丝描述的计算模型并进行了数值模拟.给出了流场的涡结构以及不同剪切率、不同扰劝强度下涡结构的特征,得到了流场中的平均速度、动量厚度.由计算被动粒子显示了流场螺旋涡结构的图像.做了相应的流动显示实验研究,所得结果与计算结果非常相近.本研究为了解该流场并由此进行流场控制提供了依据. 展开更多
关键词 流场 三维混合层 离散涡丝 数值模拟 流动显示
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Dynamic modeling and analysis of vortex filament motion using a novel curve-fitting method 被引量:2
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作者 Chang-Joo Kim Soo Hyung Park +1 位作者 Sang Kyung Sung Sung-Nam Jung 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2016年第1期53-65,共13页
Applications of a novel curve-fitting technique are presented to efficiently predict the motion of the vortex filament, which is trailed from a rigid body such as wings and rotors. The gov- erning equations of the mot... Applications of a novel curve-fitting technique are presented to efficiently predict the motion of the vortex filament, which is trailed from a rigid body such as wings and rotors. The gov- erning equations of the motion, when a Lagrangian approach with the present curve-fitting method is applied, can be transformed into an easily solvable form of the system of nonlinear ordinary dif- ferential equations. The applicability of Bezier curves, B-spline, and Lagrange interpolating polyno- mials is investigated. Local Lagrange interpolating polynomials with a shift operator are proposed as the best selection for applications, since it provides superior system characteristics with minimum computing time, compared to other methods. In addition, the Gauss quadrature formula with local refinement strategy has been developed for an accurate prediction of the induced velocity computed with the line integration of the Biot-Savart law. Rotary-wing problems including a vortex ring problem are analyzed to show the efficiency, accuracy, and flexibility in the applications of the pro- posed method. 展开更多
关键词 AERODYNAMICS Biot-Savart law Curve-fitting method Free-vortex wake Rotary wing vortex filament
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轴向涡流涡线的数值计算
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作者 阎庆绂 孙西欢 马素霞 《农业机械学报》 EI CAS CSCD 北大核心 2001年第1期46-48,共3页
在泵系统轴向涡流的测试计算基础上 ,用离散涡方法计算涡系位置的演化 ,模拟泵系统入口涡量场的轴向涡流运动 ,通过数值计算得到系统涡量场的涡线。模拟计算结果与实验测试结果基本吻合 ,为泵系统流体力学特性研究提供了新方法。
关键词 轴向涡流 涡线 计算方法
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Reconnection of Vortex Bundles Lines with Sinusoidally
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作者 Sultan Z. Alamri Abeer A. Alenezi 《Applied Mathematics》 2013年第6期945-949,共5页
Using the vortex filament model with the full Biot-Savart law, we show that non-straight bundles of quantized vortex lines in HeII are structurally robust and can reconnect with each other maintaining their identity. ... Using the vortex filament model with the full Biot-Savart law, we show that non-straight bundles of quantized vortex lines in HeII are structurally robust and can reconnect with each other maintaining their identity. We discuss vortex stretching in superfluid turbulence in many cases. We show that, during the bundle reconnection process, Kelvin waves of large amplitude are generated, in agreement with previous work and with the finding that helicity is produced by nearly singular vortex interactions in classical Euler flows. The reconnection events lead to changes in velocities, radius, number of points and total length. The existence of reconnections was confirmed by other authors using the model of nonlinear Schr?dinger equation (NLSE). Our results are agreed with the finding of other authors and extension to our numerical experiments. 展开更多
关键词 Numerical Simulation SUPERFLUID TURBULENCE vortex filament vortex RECONNECTION
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基于涡丝模型的烟雾仿真研究 被引量:3
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作者 陈国栋 苏志鹏 王娜 《贵州大学学报(自然科学版)》 2018年第1期57-62,共6页
烟雾仿真是近年来计算机图形学应用的热点研究方向,传统的烟雾仿真方法大致有:基于粒子系统的方法,基于网格的欧拉法,基于无网格的拉格朗日方法以及两者的混合。本文为逼真的仿真烟雾使用了基于涡丝和涡环的方法,相比于传统的使用基于... 烟雾仿真是近年来计算机图形学应用的热点研究方向,传统的烟雾仿真方法大致有:基于粒子系统的方法,基于网格的欧拉法,基于无网格的拉格朗日方法以及两者的混合。本文为逼真的仿真烟雾使用了基于涡丝和涡环的方法,相比于传统的使用基于网格的欧拉法和无网格的拉格朗日方法,本文的方法将流场描述为不断生成、运动、缠绕的涡丝和涡环。通过谐波分析建立涡丝模型避免了在涡丝伸展过程中出现采样不足的情况,从涡旋场到速度场的转换通过毕奥萨伐尔定律完成,通过实验该方法在仿真轻薄烟雾时效果较好,同时可以达到对烟雾较好的控制,烟雾渲染的速度较快,时间稳定性好。 展开更多
关键词 涡丝 谐波分析 Biot-Savart定律
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旋风分离器非稳态流场的简化分析 被引量:9
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作者 严超宇 吴小林 时铭显 《流体机械》 CSCD 2002年第3期18-21,38,共5页
定性分析了非稳态旋进涡核在旋风分离器流场中的运动形式及其对流场的影响。按照涡丝在流场中产生诱导速度的原理 ,提出了旋风分离器流场中有旋进涡核存在时流场的计算方法 ,通过计算值与实测值的比较发现两者吻合较好。
关键词 旋风分离器 旋进涡核 涡丝诱导速度 流场
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ANALYTICAL SOLUTION FOR THE VELOCITY FIELD INDUCED BY A UNIFORMLY MOVING HELICAL VORTEX FILAMENT IN CYLINDRICAL TUBE 被引量:5
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作者 LiuXiang HuangQi-bai +1 位作者 LiaoDao-xun WenGuo-zhen 《Journal of Hydrodynamics》 SCIE EI CSCD 2003年第1期111-121,共11页
A derivation of an analytical expression for the inviscid velocity fieldinduced by a single right-handed helical vortex filament is presented. The vortex filament movesuniformly and rigidly without change of form in a... A derivation of an analytical expression for the inviscid velocity fieldinduced by a single right-handed helical vortex filament is presented. The vortex filament movesuniformly and rigidly without change of form in a cylindrical tube, where the vortex filamentrotates around its axis with a constant angular velocity and translates along its axis with aconstant translational velocity. The key to solve the problem is to set up a moving cylindricalcoordinate system fixed on the vortex filament. The result shows that the velocity field is atime-periodic function, and may degenerate into Okulovs' s formula when the helical vortex filamentslips along the filament itself or stays immobile. 展开更多
关键词 analytical solution moving single helical vortex filament time-dependentvelocity field swirl pipe flow
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圆射流中拟序涡配对的数值模拟 被引量:1
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作者 林建忠 吴法理 刘中秋 《力学季刊》 CSCD 北大核心 2001年第4期408-415,共8页
用三维涡丝法结合涡丝的增加与合并技术,对不可压圆射流场,数值模拟了在扰动中加入次谐波后流场拟序涡的配对,配对情况与实验结果一致,通过对不同时刻涡量图的比较与分析,给出了次谐波初始强度对涡配对的影响,初始强度越大,涡配对出现越... 用三维涡丝法结合涡丝的增加与合并技术,对不可压圆射流场,数值模拟了在扰动中加入次谐波后流场拟序涡的配对,配对情况与实验结果一致,通过对不同时刻涡量图的比较与分析,给出了次谐波初始强度对涡配对的影响,初始强度越大,涡配对出现越早,涡配对位置越往上游移动;同时还得到了基波与次谐波初始相位差和涡配对的关系,没有相位差时,次谐波增长最快,相位差增加时,涡配对的速度降低。说明控制次谐波的初始强度和基波与次谐波的相位差,能起到控制圆射流剪切层乃至控制整个射流场的目的。 展开更多
关键词 圆射流 拟序涡配对 涡丝法 数值模拟 拟序涡 不可压 扰动 次谐波 涡量图 相位差
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轴对称射流中涡运动的三维涡丝模拟 被引量:1
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作者 刘中秋 林建忠 石兴 《科技通报》 北大核心 2002年第4期270-275,280,共7页
用三维涡丝法对轴对称不可压射流进行了数值模拟 ,描述了轴对称射流在外加扰动下产生的拟序结构随时间的发展 .文中应用了涡丝的增加与合并技术 ,模拟了在基波扰动作用下涡的卷起 ,以及在扰动中加入次谐波后涡的配对 .通过对不同时刻涡... 用三维涡丝法对轴对称不可压射流进行了数值模拟 ,描述了轴对称射流在外加扰动下产生的拟序结构随时间的发展 .文中应用了涡丝的增加与合并技术 ,模拟了在基波扰动作用下涡的卷起 ,以及在扰动中加入次谐波后涡的配对 .通过对不同时刻涡量图的比较与分析 ,说明扰动中的基波导致涡的卷起 ,次谐波控制着涡的配对 。 展开更多
关键词 轴对称射流 中涡运动 三维涡丝 拟序结构 数值模拟
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全包覆包芯纱的纺制及工艺研究 被引量:2
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作者 王建坤 郭晶 +1 位作者 郑帼 张昊 《纺织科学与工程学报》 CAS 2018年第2期1-6,15,共7页
通过实验探究普通环锭纺、赛络纺、喷气涡流纺三种纺纱方法对包芯纱包覆效果的影响,并从细纱纺制工艺角度对长丝退绕张力、捻系数、皮纱/芯纱包覆比进行单因素实验和正交实验探究细纱工艺对包芯纱包覆效果的影响。结果表明赛络纺纺制出... 通过实验探究普通环锭纺、赛络纺、喷气涡流纺三种纺纱方法对包芯纱包覆效果的影响,并从细纱纺制工艺角度对长丝退绕张力、捻系数、皮纱/芯纱包覆比进行单因素实验和正交实验探究细纱工艺对包芯纱包覆效果的影响。结果表明赛络纺纺制出的包芯纱包覆效果最佳,明显优于普通环锭纺和喷气涡流纺纺制出的包芯纱;单因素细纱工艺探讨得出长丝退绕张力在25c N^35c N,捻系数在275~300,皮纱/芯纱包覆比在70/30~80/20范围内,包芯纱的包覆效果较好。正交实验结果表明包芯纱包覆效果的最佳工艺参数为:长丝退绕张力30c N、棉/涤包覆比为70/30、捻系数275。 展开更多
关键词 包芯纱 普通环锭纺 赛络纺 涡流纺 长丝退绕张力 捻系数 包覆比
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