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Investigation of vortical flows over oscillating body using fast Lagrangian vortex method

Baoshan ZHU ,

《能源前沿（英文）》 2009年 第3卷 第3期   页码 297-306 doi: 10.1007/s11708-009-0010-4

摘要： A computational method facilitating long-time and high-resolution unsteady vortical flows is developed with the advantages of the discrete vortex methods. Both the velocity and pressure distribution of the flow field are calculated by integral formulations in combination with a fast summation algorithm. The vorticity field is described by Lagrangian representation, which is well suited to the moving boundary. Viscosity diffusion of the vorticity is considered with the core spreading model corrected by an adaptive splitting and merging algorithm. The effectiveness of the present method is examined by comparing the numerical results of unsteady separated flows which pass a cylinder and a thin cambered blade undergoing rotational oscillations with available experimental results. Interesting results about vortex shedding patterns and lock-in characteristics are provided for the thin cambered blade.

关键词： unsteady vortical flows     fast vortex method     vortex shedding     rotational oscillation     thin cambered blade    

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A fast antibiotic detection method for simplified pretreatment through spectra-based machine learning

《环境科学与工程前沿（英文）》 2022年 第16卷 第3期 doi: 10.1007/s11783-021-1472-9

摘要：

• A spectral machine learning approach is proposed for predicting mixed antibiotic.

关键词： Antibiotic contamination     Spectral detection     Machine learning    

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Multiscale stochastic finite element method on random field modeling of geotechnical problems – a fast

Xi F. XU

《结构与土木工程前沿（英文）》 2015年 第9卷 第2期   页码 107-113 doi: 10.1007/s11709-014-0268-4

摘要： The Green-function-based multiscale stochastic finite element method (MSFEM) has been formulated based on the stochastic variational principle. In this study a fast computing procedure based on the MSFEM is developed to solve random field geotechnical problems with a typical coefficient of variance less than 1. A unique fast computing advantage of the procedure enables computation performed only on those locations of interest, therefore saving a lot of computation. The numerical example on soil settlement shows that the procedure achieves significant computing efficiency compared with Monte Carlo method.

关键词： multiscale     finite element     settlement     perturbation     random field     geotechnical    

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Structural parameter design method for a fast-steering mirror based on a closed-loop bandwidth

Guozhen CHEN, Pinkuan LIU, Han DING

《机械工程前沿（英文）》 2020年 第15卷 第1期   页码 55-65 doi: 10.1007/s11465-019-0545-y

摘要： When a fast-steering mirror (FSM) system is designed, satisfying the performance requirements before fabrication and assembly is vital. This study proposes a structural parameter design approach for an FSM system based on the quantitative analysis of the required closed-loop bandwidth. First, the open-loop transfer function of the FSM system is derived. In accordance with the transfer function, the notch filter and proportional-integral (PI) feedback controller are designed as a closed-loop controller. The gains of the PI controller are determined by maximizing the closed-loop bandwidth while ensuring the robustness of the system. Then, the two unknown variables of rotational radius and stiffness in the open-loop transfer function are optimized, considering the bandwidth as a constraint condition. Finally, the structural parameters of the stage are determined on the basis of the optimized results of rotational radius and stiffness. Simulations are conducted to verify the theoretical analysis. A prototype of the FSM system is fabricated, and corresponding experimental tests are conducted. Experimental results indicate that the bandwidth of the proposed FSM system is 117.6 Hz, which satisfies the minimum bandwidth requirement of 100 Hz.

关键词： fast-steering mirror     structural parameter     PI controller     bandwidth     notch filter    

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An overview of vortex-induced vibration (VIV) of bridge decks

Teng WU, Ahsan KAREEM

《结构与土木工程前沿（英文）》 2012年 第6卷 第4期   页码 335-347 doi: 10.1007/s11709-012-0179-1

摘要： A brief overview of vortex-induced vibration (VIV) of circular cylinders is first given as most of VIV studies have been focused on this particular bluff cross-section. A critical literature review of VIV of bridge decks that highlights physical mechanisms central to VIV from a renewed perspective is provided. The discussion focuses on VIV of bridge decks from wind-tunnel experiments, full-scale observations, semi-empirical models and computational fluids dynamics (CFD) perspectives. Finally, a recently developed reduced order model (ROM) based on truncated Volterra series is introduced to model VIV of long-span bridges. This model captures successfully salient features of VIV at “lock-in” and unlike most phenomenological models offers physical significance of the model kernels.

关键词： vortex-induced vibration (VIV)     Volterra series     bridge    

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A sampling method based on URL clustering for fast web accessibility evaluation

Meng-ni ZHANG,Can WANG,Jia-jun BU,Zhi YU,Yu ZHOU,Chun CHEN

《信息与电子工程前沿（英文）》 2015年 第16卷 第6期   页码 449-456 doi: 10.1631/FITEE.1400377

摘要： When evaluating the accessibility of a large website, we rely on sampling methods to reduce the cost of evaluation. This may lead to a biased evaluation when the distribution of checkpoint violations in a website is skewed and the selected samples do not provide a good representation of the entire website. To improve sampling quality, stratified sampling methods first cluster web pages in a site and then draw samples from each cluster. In existing stratified sampling methods, however, all the pages in a website need to be analyzed for clustering, causing huge I/O and computation costs. To address this issue, we propose a novel page sampling method based on URL clustering for web accessibility evaluation, namely URLSamp. Using only the URL information for stratified page sampling, URLSamp can efficiently scale to large websites. Meanwhile, by exploiting similarities in URL patterns, URLSamp cluster pages by their generating scripts and can thus effectively detect accessibility problems from web page templates. We use a data set of 45 web sites to validate our method. Experimental results show that our URLSamp method is both effective and efficient for web accessibility evaluation.

关键词： Page sampling     URL clustering     Web accessibility evaluation    

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用可压缩流涡方法模拟叶轮机动静叶的相互作用

陈矛章,彭波

《中国工程科学》 2000年 第2卷 第2期   页码 15-23

摘要：

本课题组发展了一种扰动涡方法，用以研究叶轮机内动、静叶相互作用[1，2]。其优点是物理图画清楚，计算收敛快。它采用了一个重要假设：扰动胀量为零，从而大大简化 了计算过程。文章的目的是研究此假设的影响，并取消此假设，使扰动涡方法建立在完全严格的数学基础上。由于取消了“扰动胀量为零的假设，需要耦合求解扰动质量方程、扰动涡量输运方程和扰动能量输运方程。这是文章与文献[1，2]的主要区别。

文献[1,2]对NASA67压气机第一级内由于动、静叶间的相互作用引起的非定常流动过程作了数值模拟，并与试验结果作了对比。文章也作了同样的算例，以研究扰动胀量为零的影响。数值模拟结果表明，在引入了扰动胀量后，用扰动涡方法模拟动静干涉仍保持较好的收敛性和收敛速度，且与试验的符合程度更好。文章强调指出，即使对于非定常可压流，为满足无渗透边界条件所需的运动分量也是用椭圆类的拉普拉斯方程描述，而不是用双曲类的方程描述。“扰动胀童为零”不能等同于扰动运动为不可压。

关键词： 叶轮机     动、静叶相互作用     扰动涡方法     非定常流     可压缩流    

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A Fast Evaluation and Research Method for Exploration Potential of Oversea Basins

Hong-quan Kang,Yun-hua Deng,Huai-cun Jia,Tao Cheng,Bo Bai

《工程管理前沿（英文）》 2016年 第3卷 第4期   页码 338-342 doi: 10.15302/J-FEM-2016052

摘要： Oversea hydrocarbon exploration always faces some problems, such as multiple basin types, different exploration prospects, various exploration degrees, diverse data quantities and geological recognitions. This paper focuses on overseas basins with different exploration degrees and offers a new evaluation system and research method for fast evaluation and risk analysis on hydrocarbon potential. Based on the theory of probability, this new evaluation system evaluates each parameter and core accumulation factor with comprehensive and quantitative assignment, to accelerate geological evaluation. In addition, this paper suggests that source rock evaluation should be the core criterion in screening evaluation of poor-explored basins, and also proposes that both the exploration potential and geological recognition should drive the evaluation for basins with high exploration degrees. This new system and method, which is an effective system for fast basin evaluation, is suggested to be used in oversea evaluation and decision-making objectively, scientifically and efficiently.

关键词： geological risk analysis     probability model     evaluation factors     oversea exploration     hydrocarbon exploration    

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A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication

null

《机械工程前沿（英文）》 2014年 第9卷 第2期   页码 156-167 doi: 10.1007/s11465-014-0297-7

摘要：

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication (EHL) problems is presented. First, by introducing a special matrix splitting iteration method into the traditional compound direct iterative method, the full matrices for the linear systems of equations are transformed into sparse banded ones with any half-bandwidth; then, an extended Thomas method which can solve banded linear systems with any half-bandwidth is derived to accelerate the computing speed. Through the above two steps, the computational complexity of each iteration is reduced approximately from O(N3/3) to O(β2N), where N is the total number of nodes, and β is the half-bandwidth. Two kinds of numerical results of transient EHL line contact problems under sinusoidal excitation or pure normal approach process are obtained. The results demonstrate that the new algorithm increases computing speed several times more than the traditional compound direct iterative method with the same numerical precision. Also the results show that the new algorithm can get the best computing speed and robustness when the ratio, half-bandwidth to total number of nodes, is about 7.5%–10.0% in moderate load cases.

关键词： elastohydrodynamic lubrication     transient     line contact     matrix splitting iteration method     the Thomas method    

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Development of an axial-type fan with an optimization method

Chong-hyun CHO, Soo-yong CHO, Chaesil KIM,

《能源前沿（英文）》 2009年 第3卷 第4期   页码 414-422 doi: 10.1007/s11708-009-0038-5

摘要： An axial-type fan that operates at a relative total pressure of 671Pa and a static pressure of 560Pa with a flowrate of 416.6m/min is developed using an optimization technique based on the gradient method. Prior to the optimization of the fan blade, a three-dimensional axial-type fan blade is designed based on the free-vortex method along the radial direction. Twelve design variables are applied to the optimization of the rotor blade, and one design variable is selected for optimizing a stator which is located behind the rotor to support a fan-driving motor. The total and static pressure are applied to the restriction condition with the operating flowrate on the design point, and the efficiency is chosen as the response variable to be maximized. Through these procedures, an initial axial-fan blade designed by the free vortex method is modified to increase the efficiency with a satisfactory operating condition. The optimized fan is tested and compared with the performance obtained with the same class fan to figure out the optimization effect. The test results show that the optimized fan not only satisfies the restriction conditions but also operates at the same efficiency even though the tip clearance of the optimized fan is greater than 30%. The experimental and numerical tests show that this optimization method can improve the efficiency and operating pressures on axial-type fans.

关键词： axial-type fan     gradient method     free-vortex method     design variable     total pressure     static pressure     operating flowrate    

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Kinetic energy based model assessment and sensitivity analysis of vortex induced vibration of segmental

Nazim Abdul NARIMAN

《结构与土木工程前沿（英文）》 2017年 第11卷 第4期   页码 480-501 doi: 10.1007/s11709-017-0435-5

摘要： In this paper, semi 3D models for segmental Bridge decks are created in ABAQUS CFD program with the support of MATLAB codes to simulate and analyze vortex shedding generated due to wind excitation through considering the stationary position of the deck. Three parameters (wind speed, deck streamlined length and dynamic viscosity of the air) are dedicated to study their effects on the kinetic energy of the system in addition to the shapes and patterns of the vortices. Two benchmarks from the literature Von Karman and Dyrbye and Hansen are considered to validate the vortex shedding aspects for the CFD models. Good agreement between the results of the benchmarks and the semi 3D models has been detected. Latin hypercube experimental method is dedicated to generate the surrogate models for the kinetic energy of the system and the lift forces. Variance based sensitivity analysis is utilized to calculate the main sensitivity indices and the interaction orders for all the three parameters. The kinetic energy approach performed very well in revealing the rational effects and the roles of each parameter in the generation of vortex shedding and predicting vortex induced vibration of the deck.

关键词： vortex induced vibration     reynolds number     kinetic energy     vorticity     latin hypercube sampling    

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含空洞岩体微震定位的快速行进法——性能分析与工程应用 Article

蒋若辰, 戴峰, 刘燚, 李昂

《工程（英文）》 2021年 第7卷 第7期   页码 1023-1034 doi: 10.1016/j.eng.2020.10.019

摘要：

微震事件定位是微震监测技术的重要组成部分，用于圈定围岩损伤区。然而，复杂的地质条件会对最终的微震事件定位结果造成不利的影响。为实现含空洞复杂岩体中的高精度微震事件定位，本研究基于二阶差分形式的快速行进法，开发了微震事件定位方法。该方法基于建立的三维离散网格波速模型，通过搜索满足理论到时与实际到时之间残差最小的网格节点，实现对微震事件的定位。此外，基于二阶快速行进法的计算结果，微震破裂源到微震传感器的传播路径，可通过应用线性插值与龙格-库塔法获得。所用方法的合理性在一系列的数值仿真实验中得到了验证。提出的方法被应用于定位在猴子岩水电站地下洞室开挖过程中所记录的爆破与微震事件。爆破事件的定位结果表明，与采用均一岩体波速模型的定位结果相比，本方法能够有效减低微震事件定位误差。而对于微震事件的定位结果，通过现场的混凝土破裂与剥落，以及现场多点位移计的监测结果得到验证。本文提出的方法可提供相对更准确的岩体破裂位置，为圈定围岩损伤区工作提供便利。

关键词： 快速行进法     微震事件定位     含空洞复杂岩体     龙格-库塔法    

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Numerical investigation and analysis of heat transfer enhancement in channel by longitudinal vortex based

TAO Wenquan, WU Junmei

《能源前沿（英文）》 2008年 第2卷 第1期   页码 71-78 doi: 10.1007/s11708-008-0001-x

摘要： 3-D numerical simulations were presented for laminar flow and heat transfer characteristics in a rectangular channel with vortex generators. The effects of Reynolds number (from 800 to 3 000), the attack angle of vortex generator (from 15° to 90°) and the shape of vortex generator were examined. The numerical results were analyzed based on the field synergy principle. It is found that the inherent mechanism of the heat transfer enhancement by longitudinal vortex can be explained by the field synergy principle, that is, the second flow generated by vortex generators results in the reduction of the intersection angle between the velocity and fluid temperature gradient. The longitudinal vortex improves the field synergy of the large downstream region of longitudinal vortex generator (LVG) and the region near (LVG); however, transverse vortex only improves the synergy of the region near vortex generator. Thus, longitudinal vortex can enhance the integral heat transfer of the flow field, while transverse vortex can only enhance the local heat transfer. The synergy angle decreases with the increase of Reynolds number for the channel with LVG to differ from the result obtained from the plain channel, and the triangle winglet performs better than the rectanglar one under the same surface area condition.

关键词： inherent mechanism     integral     surface     rectanglar     longitudinal    

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Transversal tube pitch effects on local heat transfer characteristics of the flat tube bank fin mounted vortex

Liangbi WANG, Zhimin LIN, Kangjie SUN, Yuanxin DONG, Song LIU, Yongheng ZHANG,

《能源前沿（英文）》 2010年 第4卷 第3期   页码 333-345 doi: 10.1007/s11708-009-0061-6

摘要： The tube bank fin is commonly used to increase the area of the heat transfer surface with a small heat transfer coefficient of a heat exchanger. If vortex generators (VGs) are punched on the fin surface, the heat transfer performance of the fin can be improved. This paper focused on the effect of transversal tube pitch on the local heat transfer performance of the three-row flat tube bank fin mounted with VGs. On the fin surface, constructing the flow channel but without mounted VGs, the transversal tube pitch was greater, and the span averaged Nusselt number downstream was larger because fewer interactions of vortices would be generated from different VGs located upstream. When the area goodness factor was used as the criteria on the condition of one tube unit of heat exchanger for commonly used fin materials and fin thickness, the transversal tube pitch has considerable effect on the heat transfer enhancement of VGs. Large transversal tube pitch is more sensitive to fin material than to fin thickness.

关键词： heat transfer enhancement     vortex generator     finned flat tube bank     heat exchanger    

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Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

《结构与土木工程前沿（英文）》 2011年 第5卷 第4期   页码 510-517 doi: 10.1007/s11709-011-0129-3

摘要： By examining the two neighboring Haihe Bridges with semi- and full-closed bridge decks, the aerodynamic interference between the two decks on the vortex-induced vibration (VIV) and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics (CFD) method. The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks. The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge. However, those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges. Otherwise, the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges. Furthermore, an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.

关键词： separated parallel decks     vortex-induced vibration     aerodynamic interference     aerodynamic mitigation measure     semi-closed box deck     full-closed box deck    

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标题 作者 时间 类型 操作

Investigation of vortical flows over oscillating body using fast Lagrangian vortex method

Baoshan ZHU ,

期刊论文

A fast antibiotic detection method for simplified pretreatment through spectra-based machine learning

期刊论文

Multiscale stochastic finite element method on random field modeling of geotechnical problems – a fast

Xi F. XU

期刊论文

Structural parameter design method for a fast-steering mirror based on a closed-loop bandwidth

Guozhen CHEN, Pinkuan LIU, Han DING

期刊论文

An overview of vortex-induced vibration (VIV) of bridge decks

Teng WU, Ahsan KAREEM

期刊论文

A sampling method based on URL clustering for fast web accessibility evaluation

Meng-ni ZHANG,Can WANG,Jia-jun BU,Zhi YU,Yu ZHOU,Chun CHEN

期刊论文

用可压缩流涡方法模拟叶轮机动静叶的相互作用

陈矛章,彭波

期刊论文

A Fast Evaluation and Research Method for Exploration Potential of Oversea Basins

Hong-quan Kang,Yun-hua Deng,Huai-cun Jia,Tao Cheng,Bo Bai

期刊论文

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication

null

期刊论文

Development of an axial-type fan with an optimization method

Chong-hyun CHO, Soo-yong CHO, Chaesil KIM,

期刊论文

Kinetic energy based model assessment and sensitivity analysis of vortex induced vibration of segmental

Nazim Abdul NARIMAN

期刊论文

含空洞岩体微震定位的快速行进法——性能分析与工程应用

蒋若辰, 戴峰, 刘燚, 李昂

期刊论文

Numerical investigation and analysis of heat transfer enhancement in channel by longitudinal vortex based

TAO Wenquan, WU Junmei

期刊论文

Transversal tube pitch effects on local heat transfer characteristics of the flat tube bank fin mounted vortex

Liangbi WANG, Zhimin LIN, Kangjie SUN, Yuanxin DONG, Song LIU, Yongheng ZHANG,

期刊论文

Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

期刊论文