Flow-induced vibration control of a circular cylinder using rotational oscillation feedback

The effect of imposed rotation on a slender elastically mounted circular cylinder free to oscillate transversely to the incident flow has been studied experimentally in a free-surface water channel. Rotation rate and direction are imposed to be proportional to either the cylinder’s transverse displacement or the cylinder’s transverse velocity to determine the effectiveness of these rotation laws to control the dynamics of the cylinder, either to reduce or to enhance oscillations. The former can be of interest for energy harvesting purposes whereas the latter can be useful to avoid unwanted oscillations. In all cases, non-dimensional mass and damping are fixed ($m^{\ast }=11.7$, $\unicode[STIX]{x1D701}=0.0043$) so the analysis is focused on the role of the rotation law and the reduced velocity. The Reynolds number based on the diameter of the cylinder ranges from 1500 to 10 000. Results are presented in terms of steady-state oscillation characterization (say, amplitude and frequency) and wake-pattern topology, which was obtained through digital particle image velocimetry. Both laws are able to either reduce or enhance oscillations, but they do it in a different way. A rotation law proportional to the cylinder’s displacement is more effective to enhance oscillations. For high enough actuation, a galloping-type response has been found, with a persistent growth of the amplitude of oscillations with the reduced velocity that shows a new desynchronized mode of vortex shedding. On the other hand, a rotation law proportional to the cylinder’s transverse velocity is more efficient to reduce oscillations. In this case only vortex-induced-type responses have been found. A quasi-steady theoretical model has been developed, which helps to explain why a galloping-type response may appear when rotation is proportional to cylinder displacement and is able to predict reasonably the amplitude of oscillations in those cases. The model also explains why a galloping-type response is not expected to occur when rotation is proportional to the cylinder’s velocity.

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Energy Concentration by Bluff Bodies—A Particle Image Velocimetry Investigation

Journal of Fluids Engineering ◽

10.1115/1.4041886 ◽

2018 ◽

Vol 141 (6) ◽

Author(s):

Eshodarar Manickam Sureshkumar ◽

Maziar Arjomandi ◽

Bassam B. Dally ◽

Benjamin S. Cazzolato ◽

Mergen H. Ghayesh

Keyword(s):

Particle Image Velocimetry ◽

Circular Cylinder ◽

Bluff Body ◽

Particle Image ◽

Transverse Velocity ◽

Water Channel ◽

Energy Concentration ◽

Backward Facing Step ◽

Flow Energy ◽

Image Velocimetry

Particle image velocimetry (PIV) of four cylinders with different cross sections were performed in a recirculating water channel at Reynolds numbers of 5000 and 10,000. The cylinders were split into two distinct categories; semicircular and convex-edged triangular (c-triangular) prisms which have a smooth diverging fore-face and a flat, backward facing step aft-face, and a trapezoid which has a flat fore face and a backward-facing step aft-face. The resulting streamwise and transverse velocity vectors (u and v, respectively) were analyzed to provide a qualitative comparison of the bluff body wakes to the circular cylinder, which is the standard upstream stationary body in wake-induced vibration (WIV) energy technology. The Reynolds stresses, turbulent kinetic energy (TKE), mean spanwise vorticity, and the energy in the fluctuating component of the wake were compared. The main findings are: (i) a convex fore-face and a backward-facing step aft face are more effective at converting the flow energy to temporal wake energy (+20%) compared to a circular cylinder, (ii) a trapezoid type shape is less effective at converting flow energy to temporal wake energy (−40%) compared to a circular cylinder, (iii) increasing Reynolds number reduces the efficiency of conversion of upstream flow energy to downstream transverse temporal energy. Utilizing stationary upstream bodies such as the semicircle and the c-triangle can result in concentrating more energy in the fluctuating components for the downstream transversely vibrating bluff body in a WIV system, and hence can realize in more efficient WIV technology.

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Spring-Arrangement Effect on Flow-Induced Vibration of a Circular Cylinder

Journal of Vibration Engineering & Technologies ◽

10.1007/s42417-020-00268-5 ◽

2021 ◽

Author(s):

Koki Yamada ◽

Yuga Shigeyoshi ◽

Shuangjing Chen ◽

Yoshiki Nishi

Keyword(s):

Circular Cylinder ◽

Dynamic Model ◽

Geometric Nonlinearity ◽

Water Channel ◽

Fluid Flows ◽

Flow Induced Vibration ◽

Theoretical Evaluation ◽

Circulating Water ◽

Linear Dynamic ◽

Elastically Supported

Abstract Purpose This study elucidated the effect of an inclined spring arrangement on the flow-induced vibration of a circular cylinder to understand if the effect enhances the harnessing of the energy of fluid flows. Method An experiment was conducted on a circulating water channel. A circular cylinder was partially submerged. It was elastically supported by two springs whose longitudinal directions were varied. With the speed of the water flow varied, the vibrations of the circular cylinder were measured. The measured vibrations were interpreted by la linear dynamic model. Results and discussion In a few cases, a jump in response amplitudes from zero to the maximum was observed with the spring inclination at reduced velocities of 6 to 7, whereas gradually increasing response amplitudes were observed in other cases. The inclined spring arrangement achieved greater velocity amplitudes than in cases without spring inclination. A theoretical evaluation of the measured responses indicates that the effect of the inclined springs was caused by geometric nonlinearity; the effect would be more prominent by employing a longer moment lever.

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Buoyancy Effect on the Wake of a Confined Circular Cylinder during Opposing Laminar Mixed Convection Heat Transfer

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.390.675 ◽

2013 ◽

Vol 390 ◽

pp. 675-679

Author(s):

Iván Guillén ◽

Cesar Treviño ◽

Lorenzo Martínez-Suástegui

Keyword(s):

Circular Cylinder ◽

Mixed Convection ◽

Richardson Number ◽

Water Channel ◽

Convection Heat Transfer ◽

Buoyancy Effect ◽

Piv Measurements ◽

Laminar Mixed Convection ◽

Image Velocimetry ◽

Mixed Convection Heat Transfer

Particle image velocimetry (PIV) measurements are carried out in an experimental investigation of transient laminar opposing mixed convection to assess the thermal effects on the wake of an isothermal circular cylinder placed horizontally and confined inside a vertical closed-loop downward rectangular water channel. The buoyancy effect on the flow distributions are revealed for flow conditions with Reynolds number based on cylinder diameter of Re=170, blockage ratio D/H=0.287, aspect ratio, L/D=6.97 and values of the buoyancy parameter (Richardson number) of Ri=0 and 1. Results show that the wake closure length and Strouhal number slightly decrease for increasing Richardson number.

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The Passive Control of Unsteady Flow Structure Downstream of a Circular Cylinder in Shallow Water

Volume 1: Advances in Aerodynamics ◽

10.1115/imece2013-65924 ◽

2013 ◽

Author(s):

Tahir Durhasan ◽

Engin Pınar ◽

Muhammed M. Aksoy ◽

Göktürk M. Özkan ◽

Hüseyin Akıllı ◽

...

Keyword(s):

Circular Cylinder ◽

Shallow Water ◽

Flow Structure ◽

Vortex Shedding ◽

Passive Control ◽

Outer Cylinder ◽

Water Channel ◽

Stream Velocity ◽

Image Velocimetry ◽

Perforated Cylinder

In the present study, it was aimed to suppress the vortex shedding occurred in the near wake of a circular cylinder (inner cylinder) by perforated cylinder (outer cylinder) in shallow water flow. The inner cylinder (Di) and outer cylinder (Do) have fixed diameters, such as Di = 50 mm and Do = 100 mm, respectively. The effect of porosity, β, was examined using four different porosity ratios, 0.3, 0.5, 0.6 and 0.8. In order to investigate the effect of arc angle of outer cylinder, α, four different arc angles, α = 360°, 180°, 150° and 120° were used. The experiments were implemented in a recirculating water channel using the particle image velocimetry, PIV technique. The depth-averaged free-stream velocity was kept constant as U∞ = 100 mm/s which corresponded to a Reynolds number of Re = 5000 based on the inner cylinder diameter. The results demonstrated that the suppression of vortex shedding is substantially achieved by perforated outer cylinder for arc angle of α = 360° at β = 0.6. Turbulence Kinetic Energy statistics show that porosity, β, is highly effective on the flow structure. In comparison with the values obtained from the case of the bare cylinder, at porosity β = 0.6, turbulence characteristics are reduced by %80. Also, the point, which the values of maximum TKE, shift to a farther downstream compared to the case of bare cylinder.

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Flow-induced vibration of D-section cylinders: an afterbody is not essential for vortex-induced vibration

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.501 ◽

2018 ◽

Vol 851 ◽

pp. 317-343 ◽

Cited By ~ 19

Author(s):

J. Zhao ◽

K. Hourigan ◽

M. C. Thompson

Keyword(s):

Circular Cylinder ◽

Water Channel ◽

Dynamic Responses ◽

Stream Velocity ◽

Mass Ratio ◽

Flow Induced Vibration ◽

Vortex Induced Vibration ◽

Fluid Forces ◽

New Findings ◽

Low Mass

While it has been known that an afterbody (i.e. the structural part of a bluff body downstream of the flow separation points) plays an important role affecting the wake characteristics and even may change the nature of the flow-induced vibration (FIV) of a structure, the question of whether an afterbody is essential for the occurrence of one particular common form of FIV, namely vortex-induced vibration (VIV), still remains. This has motivated the present study to experimentally investigate the FIV of an elastically mounted forward- or backward-facing D-section (closed semicircular) cylinder over the reduced velocity range $2.3\leqslant U^{\ast }\leqslant 20$, where $U^{\ast }=U/(f_{nw}D)$. Here, $U$ is the free-stream velocity, $D$ the cylinder diameter and $f_{nw}$ the natural frequency of the system in quiescent fluid (water). The normal orientation with the body’s flat surface facing upstream is known to be subject to another common form of FIV, galloping, while the reverse D-section with the body’s curved surface facing upstream, due to the lack of an afterbody, has previously been reported to be immune to VIV. The fluid–structure system was modelled on a low-friction air-bearing system in conjunction with a recirculating water channel facility to achieve a low mass ratio (defined as the ratio of the total oscillating mass to that of the displaced fluid mass). Interestingly, through a careful overall examination of the dynamic responses, including the vibration amplitude and frequency, fluid forces and phases, our new findings showed that the D-section exhibits a VIV-dominated response for $U^{\ast }<10$, galloping-dominated response for $U^{\ast }>12.5$, and a transition regime with a VIV–galloping interaction in between. Also observed for the first time were interesting wake modes associated with these response regimes. However, in contrast to previous studies at high Reynolds number (defined by $Re=UD/\unicode[STIX]{x1D708}$, with $\unicode[STIX]{x1D708}$ the kinematic viscosity), which have showed that the D-section was subject to ‘hard’ galloping that required a substantial initial amplitude to trigger, it was observed in the present study that the D-section can gallop softly from rest. Surprisingly, on the other hand, it was found that the reverse D-section exhibits pure VIV features. Remarkable similarities were observed in a direct comparison with a circular cylinder of the same mass ratio, in terms of the onset $U^{\ast }$ of significant vibration, the peak amplitude (only approximately 6 % less than that of the circular cylinder), and also the fluid forces and phases. Of most significance, this study shows that an afterbody is not essential for VIV at low mass and damping ratios.

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Particle image velocimetry measurement of turbulent wake past circular cylinder at Reynolds numbers from 2.5·103 to 1.5·104

MATEC Web of Conferences ◽

10.1051/matecconf/202134500030 ◽

2021 ◽

Vol 345 ◽

pp. 00030

Author(s):

Ondřej Sterly

Keyword(s):

Particle Image Velocimetry ◽

Circular Cylinder ◽

Particle Image ◽

Transverse Velocity ◽

Reynolds Numbers ◽

Particle Image Velocimetry Technique ◽

Recirculation Bubble ◽

Image Velocimetry ◽

Ensemble Statistics ◽

Vorticity Component

A canonical case of air flow past a circular cylinder is studied by using Particle Image Velocimetry technique. This contribution focus to the ensemble statistics (first and second moment) of the stream-wise and transverse velocity component as well as to the in-plane vorticity component. Although the range of explored Reynolds numbers is narrow, we observe a significant shortening of recirculation bubble within this range.

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Neuromyelitis optica spectrum: novel concept of pathogenesis, diagnosis and treatment of Devic’s disease

Orvosi Hetilap ◽

10.1556/oh.2009.28724 ◽

2009 ◽

Vol 150 (46) ◽

pp. 2101-2109 ◽

Cited By ~ 1

Author(s):

Péter Csécsei ◽

Anita Trauninger ◽

Sámuel Komoly ◽

Zsolt Illés

Keyword(s):

Neuromyelitis Optica ◽

Water Channel ◽

Diagnostic Procedures ◽

Diagnosis And Treatment ◽

Clinical Settings ◽

Permanent Disability ◽

Therapeutic Decisions ◽

Novel Concept ◽

The Brain

The identification of autoantibodies generated against the brain isoform water channel aquaporin4 in the sera of patients, changed the current diagnostic guidelines and concept of neuromyelitis optica (NMO). In a number of cases, clinical manifestation is spatially limited to myelitis or relapsing optic neuritis creating a diverse. NMO spectrum. Since prevention of relapses provides the only possibility to reduce permanent disability, early diagnosis and treatment is mandatory. In the present study, we discuss the potential role of neuroimaging and laboratory tests in differentiating the NMO spectrum from other diseases, as well as the diagnostic procedures and therapeutic options. We also present clinical cases, to provide examples of different clinical settings, diagnostic procedures and therapeutic decisions.

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Inhibition of the water channel aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide

European Heart Journal ◽

10.1093/ehjci/ehaa946.3665 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

V Montiel ◽

R Bella ◽

L Michel ◽

E Robinson ◽

J.C Jonas ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Cardiac Hypertrophy ◽

Cardiac Myocytes ◽

Cardiac Remodeling ◽

Cardiac Myocyte ◽

Water Channel ◽

Transmembrane Transport ◽

Funding Source ◽

Water Pore

Abstract Background Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but so far, strategies using systemic anti-oxidants have generally failed to prevent it. Aquaporins are a family of transmembrane water channels with thirteen isoforms currently known. Some isoforms have been implicated in oxidant signaling. AQP1 is the most abundant aquaporin in cardiovascular tissues but its specific role in cardiac remodeling remains unknown. Purpose We tested the role of AQP1 as a key regulator of oxidant-mediated cardiac remodeling amenable to targeted pharmacological therapy. Methods We used mice with genetic deletion of Aqp1 (and wild-type littermate), as well as primary isolates from the same mice and human iPSC/Engineered Heart Tissue to test the role of AQP1 in pro-hypertrophic signaling. Human cardiac myocyte-specific (PCM1+) expression of AQP's and genes involved in hypertrophic remodeling was studied by RNAseq and bioinformatic GO pathway analysis. Results RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalizes with the NADPH oxidase-2 (NOX2) and caveolin-3. We show that hydrogen peroxide (H2O2), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H2O2 through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H2O2. Deletion of Aqp1 or selective blockade of AQP1 intra-subunit pore (with Bacopaside II) inhibits H2O2 transport in mouse and human cells and rescues the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. This protective effect is due to loss of transmembrane transport of H2O2, but not water, through the intra-subunit pore of AQP1. Treatment of mice with clinically-approved Bacopaside extract (CDRI08) inhibitor of AQP1 attenuates cardiac hypertrophy and fibrosis. Conclusion We provide the first demonstration that AQP1 functions as an aqua-peroxiporin in primary rodent and human cardiac parenchymal cells. We show that cardiac hypertrophy is mediated by the transmembrane transport of H2O2 through the AQP1 water channel. Our studies open the way to complement the therapeutic armamentarium with specific blockers of AQP1 for the prevention of adverse remodeling in many cardiovascular diseases leading to heart failure. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): FRS-FNRS, Welbio

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