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A Review on Vibration Control of Multiple Cylinders Subjected to FlowInduced Vibrations

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China Ocean Engineering 2024年第2期38卷 183-197页

作者： XU wan-hai MA Ye-xuan State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300350China Institute of Mechanics Chinese Academy of SciencesBeijing 100190China

The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering *** FIV suppression is of great importance for the security of many cylindrical *** active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated *** to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV *** efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two *** control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control *** FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and *** FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence *** research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.

关键词： flow-induced vibration vibration control multiple cylinders tandem side-by-side staggered

Iptakalim,an ATP-sensitive potassium channel opener,confers neuroprotection against cerebral ischemia/reperfusion injury in rats by protecting neurovascular unit cells

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2011年第10期12卷 835-845页

作者： Yu-hua RAN hai wan Institute of Health and Environmental Medicine Academy of Military Medical Sciences Beijing 100850 China Thadweik Academy of Medicine Beijing 100039 China

Objective:To investigate the role of iptakalim,an ATP-sensitive potassium channel opener,in transient cerebral ischemia/reperfusion (I/R) injury and its involved ***:Intraluminal occlusion of middle cerebral artery (MCAO) in a rat model was used to investigate the effect of iptakalim at different time *** volume was measured by staining with 2,3,5-triphenyltetrazolium chloride,and immunohistochemistry was used to evaluate the expressions of Bcl-2 and *** vitro,neurovascular unit (NVU) cells,including rat primary cortical neurons,astrocytes,and cerebral microvascular endothelial cells,were cultured and underwent oxygen-glucose deprivation (OGD).The protective effect of iptakalim on NVU cells was investigated by cell viability and injury assessments,which were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and release of lactate ***-3,Bcl-2 and Bax mRNA expressions were evaluated by real-time polymerase chain reaction (PCR).Results:Administration of iptakalim 0 or 1 h after reperfusion significantly reduced infarct volumes,improved neurological scores,and attenuated brain edema after cerebral I/R *** treatment (0 h after reperfusion) also reduced caspase-3 expression and increased the ratio of Bcl-2 to Bax by *** inhibited OGD-induced cell death in cultured neurons and astrocytes,and lactate dehydrogenase release from cerebral microvascular endothelial *** reduced mRNA expression of caspase-3 and increased the ratio of Bcl-2 to Bax in NVU ***:Iptakalim confers neuroprotection against cerebral I/R injury by protecting NVU cells via inhibiting of apoptosis.

关键词： Neurovascular unit Cerebral ischemia/reperfusion (I/R) injury ATP-sensitive potassium channel opener Neuroprotection Apoptosis

Application Specified Soft-Error Failure Rate Analysis Using Sequential Equivalence Checking Techniques

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Tsinghua Science and Technology 2020年第1期25卷 103-116页

作者： Tun Li Qinhan Yu hai wan Sikun Li School of Computer Science National University of Defense TechnologyChangsha 410073China the Laboratory of Software Engineering for Complex Systems National University of Defense TechnologyChangsha 410073China. School of Software Tsinghua UniversityBeijing 100084China

Soft errors have become a critical challenge as a result of technology scaling. Existing circuit-hardening techniques are commonly associated with prohibitive overhead of performance, area, and power. However,evaluating the influence of soft errors in Flip-Flops(FFs) on the failure of circuit is a difficult verification ***, we proposed a novel flip-flop soft-error failure rate analysis methodology using a formal method with respect to application behaviors. Approach and optimization techniques to implement the proposed methodology based on the given formula using Sequential Equivalence Checking(SEC) are introduced. The proposed method combines the advantage of formal technique-based approaches in completeness and the advantage of application behaviors in accuracy to differentiate vulnerability of components. As a result, the FFs in a circuit are sorted by their failure rates, and designers can use this information to perform optimal hardening of selected sequential components against soft errors. Experimental results of an implementation of a SpaceWire end node and the largest ISCAS’89 benchmark sequential circuits indicate the feasibility and potential scalability of our approach. A case study on an instruction decoder of a practical 32-bit microprocessor demonstrates the applicability of our method.

关键词： soft error failure rate analysis Sequential Equivalence Checking(SEC) application specified

The prediction on in-line vortex-induced vibration of slender marine structures

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Acta Mechanica Sinica 2012年第5期28卷 1303-1308页

作者： wan-hai Xu Xi-Feng Gao Jie Du State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Civil EngineeringTianjin University

The in-line （IL） vortex-induced vibration （VIV） that occurs frequently in ocean engineering may cause severe fatigue damage in slender marine structures. To the best knowledge of the authors, in existing literatures, there is no efficient analytical model for predicting pure IL VIV. In this paper, a wake oscillator model capable of analyzing the IL VIV of slender marine structures has been developed. Two different kinds of van der Pol equations are used to describe the near wake dynamics related to the fluctuating nature of symmetric vortex shedding in the first excitation region and alternate vortex shedding in the second one. Some comparisons are carried out between the present model results and experimental data. It is found that many phenomena observed in experiments could be reproduced by the present wake oscillator model.

关键词： Vortex-induced vibration Wake oscillatormodel In-line Slender marine structures

Probabilistic Modeling and Optimization of Real-Time Protocol for Multifunction Vehicle Bus

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Tsinghua Science and Technology 2016年第5期21卷 561-569页

作者： Lifan Su Min Zhou hai wan Ming Gu School of Software Tsinghua University Beijing 100084 China

In this paper, we present the modeling and optimization of a Real-Time Protocol（RTP） used in Train Communication Networks（TCN）. In the proposed RTP, message arbitration is represented by a probabilistic model and the number of arbitration checks is minimized by using the probability of device activity. Our optimized protocol is fully compatible with the original standard and can thus be implemented easily. The experimental results demonstrate that the proposed algorithm can reduce the number of checks by about 50%, thus significantly enhancing bandwidth.

关键词： train communication network probabilistic modelling protocol optimization

Use of Helical Strakes for FIV Suppression of Two Inclined Flexible Cylinders in A Side-by-Side Arrangement

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China Ocean Engineering 2018年第3期32卷 331-340页

作者： XU wan-hai ZHANG Shu-hai ZHOU Li-dan GAO Xi-feng State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Collaborative Innovation Centre for Advanced Ship and Deep-Sea Exploration Shanghai 200240China

The experimental studies on flow-induced vibrations(FIV) reduction of two side-by-side flexible cylinders inclined at 45° by using the helical strakes were carried out in a towing tank. The main aim of the experiment is to check whether the helical strakes with a pitch of 17.5 D and a height of 0.25 D, which is considered as the most effective vibration suppression device for the isolated cylinder undergoing vortex-shedding, still perform very well to reduce FIV of two inclined flexible cylinders in a side-by-side arrangement. The vibration of two identical inclined cylinders with a mass ratio of 1.90 and an aspect ratio of 350 was tested in the experiment. The center-to-center distance between the two cylinders was 3.0 D. The uniform flow was simulated by towing the cylinder models along the *** towing velocity varied from 0.05 to 1.0 m/s with an interval of 0.05 m/s. The maximum Reynolds number can be up to 1.6×104. Three cases were experimentally studied in this paper, including two side-by-side inclined smooth cylinders, only one smooth cylinder fitted with helical strakes in the two side-by-side inclined cylinders system and both two cylinders attached with helical strakes. The variations of displacement amplitude, dominant frequency, FIV suppression efficiency and dominant mode for the two side-by-side inclined cylinders with reduced velocity were shown and discussed.

关键词： helical strakes FIV suppression inclined cylinder side-by-side towing tank experiment

Vortex-Induced Vibrations of A Free-Spanning Pipe Based on A Nonlinear Hysteretic Soil Model at the Shoulders

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China Ocean Engineering 2020年第3期34卷 328-340页

作者： GAO Xi-feng XIE Wu-de XU wan-hai State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

The pipe-soil interactions at shoulders can significantly affect the vortex-induced vibrations (VIV) of free-spanning pipes in the subsea. In this paper, the seabed soil reacting force on the pipe is directly calculated with a nonlinear hysteretic soil model. For the VIV in the middle span, a classic van der Pol wake oscillator is adopted. Based on the Euler-Bernoulli beam theory, the vibration equations of the pipe are obtained which are different in the middle span and at the two end shoulders. The static configuration of the pipe is firstly calculated and then the VIV is *** present model is validated with the comparisons of VIV experiment, pipe-soil interaction experiment and the simulation results of VIV of free-spanning pipes in which the seabed soil is modelled with spring-dashpots. With the present model, the influence of seabed soil on the VIV of a free-spanning pipe is analyzed. The parametric studies show that when the seabed soil has a larger suction area, the pipe vibrates with smaller bending stresses and is *** with the increase of the shear strength of the seabed soil, the bending stresses increase and the pipe faces more danger.

关键词： free-spanning pipe vortex-induced vibrations nonlinear hysteretic soil model bending stresses

Flow-Induced Vibration Fatigue Damage of A Pair of Flexible Cylinders in A Staggered Array

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China Ocean Engineering 2021年第6期35卷 878-890页

作者： XU wan-hai LI Yu-han JIA Kun LAI Jiang State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Nuclear Power Institute of China Chengdu 610041China

Flow-induced vibration(FIV)of a group of long,flexible cylinders involves a complex interaction between fluid and *** a substantial number of studies have been devoted to assessing FIV response behaviours,fatigue damage features of staggered flexible cylinders are not fully ***,the wake-induced flutter constitutes an intricate hydrodynamic behaviour that frequently occurs when one cylinder is in the vicinity of another ***,existing studies on the fatigue damage caused by wake-induced flutter are incapable of achieving better *** paper,therefore,estimates the FIV fatigue damage of two staggered flexible cylinders with an aspect ratio of 350 and a mass ratio of 1.90 based on normal S−N curves according to Det Norske Veritas(DNV)*** staggered cases(cross-flow spacing ratios of 2.0,3.0,4.0,and 6.0 and in-line spacing ratios of 4.0,6.0,and 8.0)are discussed for comparison,and fatigue damage caused by wake-induced flutter is thoroughly *** damage results indicate that the variation of the cross-flow(CF)spacing ratio has a greater influence than that of the in-line(IL)spacing ratio on the CF fatigue damage of the upstream *** IL fatigue damages of the upstream cylinder are observed when reduced velocity V_(r)≥15.03 due to the wake flow patterns with different IL spacing ***,wake interference,especially wake-induced flutter,predominates the fatigue damage characteristics of the downstream *** V_(r)=8.77−11.27,wake-induced flutter enhances the IL fatigue damage of the downstream cylinder and slightly affects that of the upstream ***,wake-induced flutter causes considerable IL fatigue damage disparity between the two staggered cylinders by suppressing the IL fatigue damage of the upstream cylinder when V_(r)≥20.04.

关键词： flow-induced vibration fatigue damage flexible cylinder staggered arrangement wake-induced flutter

A Novel Wake Oscillator Model for Vortex-Induced Vibrations Prediction of A Cylinder Considering the Influence of Reynolds Number

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China Ocean Engineering 2018年第2期32卷 132-143页

作者： GAO Xi-feng XIE Wu-de XU wan-hai BAI Yu-chuan ZHU hai-tao State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Collaborative Innovation Centre for Advanced Ship and Deep-Sea Exploration Shanghai 200240China

It is well known that the Reynolds number has a significant effect on the vortex-induced vibrations(VIV) of cylinders. In this paper, a novel in-line(IL) and cross-flow(CF) coupling VIV prediction model for circular cylinders has been proposed, in which the influence of the Reynolds number was comprehensively considered. The Strouhal number linked with the vortex shedding frequency was calculated through a function of the Reynolds number. The coefficient of the mean drag force was fitted as a new piecewise function of the Reynolds number, and its amplification resulted from the CF VIV was also taken into account. The oscillating drag and lift forces were modelled with classical van der Pol wake oscillators and their empirical parameters were determined based on the lock-in boundaries and the peak-amplitude formulas. A new peak-amplitude formula for the IL VIV was developed under the resonance condition with respect to the mass-damping ratio and the Reynolds number. When compared with the results from the experiments and some other prediction models, the present model could give good estimations on the vibration amplitudes and frequencies of the VIV both for elastically-mounted rigid and long flexible cylinders. The present model considering the influence of the Reynolds number could generally provide better results than that neglecting the effect of the Reynolds number.

关键词： vortex-induced vibrations Reynolds number wake oscillator model cylinder