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Journal of Hydrodynamics 2024年第2期36卷 378-393页

作者： Lin Zou Di-wei Liu Jian Liu Hong-cheng Zuo Yin-huan Zheng Hao Xia School of Mechanical and Electronic Engineering Wuhan University of TechnologyWuhan430070China Department of Aeronautical and Automotive Engineering Loughborough UniversityLoughboroughUK

The wake induced vibration(WIV)of a one-and two-degree-of-freedom(1DOF,2DOF)downstream wave-cone cylinder(WCC)behind a stationary equal-size upstream wave-cone cylinder in the staggered arrangement is numerically investigated at subcritical Reynolds number of 3900 by using shear stressed transfer(SST)k-ωturbulence *** streamwise pitch ratios(P/Dm)vary from 4 to 6 with a fixed incident angleα=8°.Experimental measurements were also performed for the validation of the present numerical *** is found that the largest vibration amplitude in crossflow direction occurred at P/Dm=4,Ur=8 with small difference of streamwise vibration at P/Dm=4,*** from single wavy-cone cylinder(SWCC),the downstream flexible one of a pair staggered WCCs got larger vibration amplitude during phase switching stage instead of in-phase *** upstream wake will suppress the triple frequency of main frequency in the power spectra density(PSD)functions of Cl but stimulate the double one of *** intriguing vibration mechanism happened in all 2DOF cases where the trajectory of downstream WCC is a significant ellipse rather than a figure of *** transformation of phase switching and the variation of the main frequency of drag coefficient(Cd)can be explained by the vortex-shedding modes of downstream WCC.

关键词： Two wave-cone cylinders staggered arrangement wake induced vibration phase switching vortex shedding

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

Passive Control of Flow-Induced Vibration(FIV)by Helical Strakes for Two staggered Flexible Cylinders

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China Ocean Engineering 2021年第4期35卷 475-489页

作者： XU Wan-hai WANG Qi-cheng QIN Wen-qi DU Zun-feng State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China CIMC Offshore Co.Ltd Shenzhen 518000China

Helical strake is a widely-used device for passive flow-induced vibration(FIV)control of cylindrical *** is omnidirectional and can effectively reduce FIV response *** on the passive FIV control for cylindrical structures are mainly concerned with a single isolated cylinder,while the influence of wake interference between multiple cylinders on FIV suppression devices is less considered up to *** engineering applications,multiple flexible cylinders with large aspect ratios can be subjected to complex flow forces,and the effects of wake interference are *** FIV suppression effect of helical strake of a common configuration(17.5D pitch and 0.25D height,where D is the cylinder diameter)in two staggered cylinders system is still *** paper systematically studied the FIV response of multiple cylinders system fitted with the helical strakes by model *** relative spatial position of the two cylinders is fixed at S=3.0D and T=8.0D,which ensures the cylindrical structures in the flow interference *** experimental results show that the helical strakes effectively reduce the FIV response on staggered upstream cylinder,and the suppression efficiency is barely affected by the smooth or straked downstream *** corresponding FIV suppression efficiency on the downstream cylinder is remarkably reduced by the influence of the upstream wake *** wake-induced vibration(WIV)phenomenon is not observed on the staggered downstream cylinder,which normally occurs on the downstream straked cylinder in a tandem arrangement.

关键词： flow-induced vibration(FIV) passive control helical strakes flexible cylinders staggered arrangement

Simulation Study on Flow and Heat Transfer of Cross-arrangement Tube Bundle

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Journal of Thermal Science 2023年第4期32卷 1435-1444页

作者： LI Shuangfei LI Jinjing LIU Zhenhua School of Mechanical Engineering Shanghai Jiaotong UniversityShanghai200240China

The air precooler of SABRE engine(Synergetic Air-Breathing Rocket Engine)is a tube bundle type of heat exchanger consisting of thousands of small *** cold helium gas flows in the small tube bundle,and the high-speed hot air circulates outside the tubes and exchanges heat with the helium in the *** this study,the cross-arrangement tube bundle consisting of small tubes with outer diameter of 1mm was taken as the research *** system simulation calculation and data sorting were carried *** is found that the empirical correlation of the conventional tube bundle is no longer applicable to the small tube and the reasons for inapplicability are explained by analysis of flow *** addition,the results show that the average heat transfer coefficient of cross small/micro tube bundle isn’t affected by heat flux,but increases with the increase of Reynolds number,increases with the increase of transverse spacing,and decreases with the increase of longitudinal *** flow resistance coefficient isn’t affected by heat flux and longitudinal spacing,but decreases with the increase of Reynolds number,and decreases with the increase of transverse spacing.

关键词： staggered arrangement small tube fitting formulas air cooler SABRE engine

Local buckling analysis of biological nanocomposites based on a beam-spring model

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Theoretical & Applied Mechanics Letters 2015年第4期5卷 146-150页

作者： Zhiling Bai Baohua Ji Biomechanics and Biomaterials Laboratory Department of Applied Mechanics School of Aerospace Engineering Beijing Institute of Technology

Biological materials such as bone, tooth, and nacre are load-bearing nanocomposites composed of mineral and protein. Since the mineral crystals often have slender geometry, the nanocomposites are susceptible to buckle under the compressive load. In this paper, we analyze the local buckling behaviors of the nanocomposite structure of the biological materials using a beam-spring model by which we can consider plenty of mineral crystals and their interaction in our analysis compared with existing studies. We show that there is a transition of the buckling behaviors from a local buckling mode to a global one when we continuously increase the aspect ratio of mineral, leading to an increase of the buckling strength which levels off to the strength of the composites reinforced with continuous crystals. We find that the contact condition at the mineral tips has a striking effect on the local buckling mode at small aspect ratio, but the effect diminishes when the aspect ratio is large. Our analyses also show that the staggered arrangement of mineral plays a central role in the stability of the biological nanocomposites.

关键词： Biological materials Nanostructure staggered arrangement Buckling behaviors Aspect ratio Composite materials