Response Of Cylinder Research Articles

Wake galloping energy harvesting in heat exchange systems under the influence of ash deposition

Since the fluid flows in heat exchange systems contain hydrokinetic energies, flow-induced vibration (FIV) energy harvesting technology can be potentially applied to collect electrical energy. Different from the applications in traditional scenarios, cylinder bluff bodies implemented in the heat exchange systems will inevitably suffer from ash deposition. This study proposes a wake galloping energy harvester to be used in heat exchange systems and focuses on investigating the effects of different ash deposition types on the energy harvesting performance. According to different ash deposition types, bell-shaped and horn-shaped cylinder bluff bodies are designed to consider the ash deposition effect. Wind tunnel experiments are conducted to investigate the performance of the wake galloping piezoelectric energy harvester (PEH) with different upstream ash deposit cylinders, at various space distances and under different wind speeds. The experimental results reveal that compared to the horn-shaped cylinder, the bell-shaped cylinder is more beneficial for energy harvesting. Among all tested cases, the optimal configuration is determined: the upstream cylinder is attached by bell-shaped ash deposition; and the space ratio between the upstream and the downstream cylinders is 1.5. The threshold wind speed of the optimal configuration is reduced and the maximum voltage output is improved by over 111%. It is learned that the two types of upstream ash deposit cylinders can both cause the quenching phenomenon to deteriorate the performance of the energy harvester. Guidelines based on the experimental results are provided to avoid the occurrence of the quenching phenomenon. Computational fluid dynamics (CFD) studies are conducted to reveal the underlying mechanisms to explain the experimental results. The CFD results corroborate that different ash deposit cylinders produce different wake vortices and the flow pattern changes with the space distance, which determines the dynamic response of the downstream cylinder.

Flow-Induced Vibration of Solitary Wire-Wrapped Cylinders in Axial Flow

Vibration of nuclear power plant components can cause fretting wear and fatigue that can eventually lead to component failure. Flexible, high-aspect-ratio components under flow, such as the wire-wrapped cylindrical fuel elements in a liquid metal-cooled fast reactor core, are particularly susceptible to vibration due to their low natural frequencies. The flow-induced vibrations experienced by such components tend to be random and of low amplitude and frequency; however, at critical flow velocities these components can experience self-excited, fluid-elastic instabilities that can lead to immediate failure. Such failures of critical reactor components, particularly those that act as fission product barriers, can lead to prolonged shutdowns of nuclear power plants and even to their permanent closure. Thus, a better understanding of the vibration response of wire-wrapped cylinders in axial flow is needed. This study details the development of a theoretical model that incorporates the effects of a helical wire wrap along a cylinder to understand its impact on the dynamic response of the cylinder under flow. This theoretical model is compared against experimental vibration data of varying geometries of solitary wire-wrapped cylinders in confined axial flow. The results of this study provide an improved knowledge of how a helical wire wrap can affect the dynamic response of a cylinder under flow.

Elastic response of a hollow cylinder with voids and micropolar structure

Elastic response of a hollow cylinder with voids and micropolar structure

Rotational flexural strength of cylindrical brittle specimens

AbstractConventional static flexural strength testing of brittle cylindrical rods only subjects a small fraction of the entire specimen's area or volume to the maximum tensile stress. Thus, a nonconservative measured strength likely results since most flaws on the surface or in the bulk are not subjected to a sufficiently high tensile stress that can cause fracture. To mitigate this, a rotational flexural tester and corresponding test method were developed whereby rotation and monotonically increasing three‐point flexure were superimposed to investigate fracture response of solid glass cylinders. This combination of rotation and flexure subjects more area and volume of a cylindrical test specimen to tensile stress than a standard static (nonrotating) flexural test. As anticipated, failure stresses were lower for the rotational flexural test. Expressions for effective area and volume are provided for rotating solid rods and tubes subjected to three‐point, four‐point, uniform, and uniformly distributed load bending configurations.

A coupled model for vortex induced vibration of a circular cylinder with and without passive-jet flow control

In the present study, a coupled wake oscillator dynamic equation was established to predict the vortex-induced vibration (VIV) response of a circular cylinder immersed in a fluid. A classical structural dynamic equation was applied to describe the one-degree-of-freedom vibration of a circular cylinder. The revised van der Pol equation was used to model the wake flow dynamics and the fluctuating aerodynamic force derived from periodic alternating vortex shedding. The coupled structural dynamic equation and revised van der Pol equation were utilized to describe the features of VIV, such as the frequency component of aerodynamic forces, vibration amplitude, and lock-in domains. The results show that the proposed model can more precisely predict the VIV response and frequency features. An experiment was performed to study the passive jet flow control for VIV of a circular cylinder. The surface pressure distribution was measured to obtain the sectional aerodynamic forces acting on the model containing passive jet rings with different distances. The influencing range of the aerodynamic force caused by the passive jet rings was obtained and incorporated into the coupled model. The revised coupled model was found to predict well the VIV response of a circular cylinder equipped with adjacent passive jet rings having different distances.

Transient thermomechanical sensitivity analysis using a complex-variable finite element method

A complex-variable transient thermomechanical element was developed and used to compute highly accurate sensitivities of the thermal and stress time-dependent responses of a thick-walled cylinder with temperature-dependent material properties with respect to fifteen material, shape, and loading parameters using the complex Taylor series expansion method (CTSE). The analysis was conducted by employing a complex-variable user element within the Abaqus commercial finite element software, herein called ZFEM, using real and imaginary nodal degrees of freedom (DOF). The real coordinates denote the spatial coordinates, as typical, and the imaginary nodal DOF denote the perturbation of the geometry for shape sensitivities. Upon completion, the imaginary DOF hold the partial derivatives of the temperature and the displacements with respect to the parameter of interest. Sensitivities of stresses were obtained using the displacement sensitivities. The sensitivities were verified by a comparison with finite difference estimates using the built-in Abaqus elements. The numerical results demonstrate the superior accuracy, ease of use, and reduced run-time of ZFEM compared to the finite difference method. The conclusions show that ZFEM can be utilized to obtain time-dependent sensitivities with high accuracy and precision for transient thermomechanical analyses that are computationally more efficient in comparison to finite difference methods.

Flow-induced vibration control of a circular cylinder by using flexible and rigid splitter plates

Flow-induced vibration (FIV) control of a circular cylinder by using a flexible splitter plate attached to the rear stagnation point is experimentally investigated. The rigid splitter plate is also applied to highlight the unique feature of the flexible splitter plate. A platform has been designed to ensure that the cylinder can only vibrate in the transverse direction. The Reynolds numbers based on the cylinder diameter and the free-stream velocity are in the range of 1680–8720. When a flexible or rigid splitter plate is attached, the vibration response of the circular cylinder is different. The vortex-induced vibration (VIV) and galloping are both observed for the rigid splitter plate cases. Though the vibration amplitude in the synchronization region is reduced by the rigid splitter plate, it increases linearly with the reduced velocity at large reduced velocities. However, the flexible splitter plate with a streamwise length greater than one cylinder diameter performs well in suppression of the vibration, and the reduction in the maximum amplitude reaches about 91% compared with the natural case. The flow pattern in the wake is changed by the splitter plate. The interaction between upper and lower shear layers is reduced, especially in the near-wake region. The shear layers shedding from the cylinder do not alternately reattach on the tip of the flexible splitter plate, thus, the galloping does not occur.

Understanding the higher harmonics of vortex-induced vibration response using a trend-constrained, machine learning approach

The spectra from cross-flow VIV signals contain peaks at the dominant vortex shedding frequency but also at several other frequencies, notably at three times and five times that frequency. These higher harmonic contributions are important because they are associated with high fatigue damage rates. The understanding of what controls higher harmonic response is far from complete. This paper presents a trend-constrained, data-driven model to discover important features (parameters) affecting the higher harmonic response of flexible cylinders subjected to vortex-induced vibrations. The predicted dependent parameter is the ratio of stress at the 3rd harmonic divided by the stress at the dominant VIV frequency. The known effects of damping and bending stiffness are introduced as physical constraints to improve the DNN predictions and aid in important parameter identification. The machine learning predictions with and without prior physical constraints are compared. The comparison suggests that the machine learning model with prior physical constraints better handles independent experimental datasets. It is confirmed that the higher stress ratios are associated with smaller damping parameter values and smaller bending stiffness ratios. The larger stress ratio is also found to be associated with traveling waves and single-mode-dominated responses.

Numerical simulation of dynamic response and failure of large-diameter thin-walled cylinder under vibratory penetration

Large-diameter thin-walled steel cylinders, which were first used in the Hong Kong-Zhuhai-Macao Bridge project as an enclosure structure for artificial islands, have been applied in many large-scale offshore projects. The thin-walled steel cylinder may fail during vibratory penetration in certain conditions such as asynchronicity of hammers and presence of corestones or sloping rockhead, which cannot be accommodated in routine wave equation analysis. This study aims to further develop the novel thin-walled offshore retaining structure. A three-dimensional (3D) finite element model is established to simulate the penetration of large-diameter thin-walled steel cylinders using a group of vibratory hammers. The dynamic response of the steel cylinder under multi-point vibrations is sensitive to penetration depth, vibration amplitude, and frequency. Failure under unsynchronized vibrations occurs first at the free part of the cylinder above the ground level. A “shearing” failure mode can develop when the asynchronous hammers cluster together and a “shearing-compressive” failure mode can develop when the asynchronous hammers are alternately distributed. Failure of the cylinder in the presence of geological obstacles occurs at the cylinder toe. “Compressive buckling” and “extrusion buckling” failure modes can develop when the steel cylinder encounters a corestone and sloping rockhead, respectively.

Secondary Creep Analysis of FG Rotating Cylinder with Exponential, Linear and Quadratic Volume Reinforcement.

Creep is an irreversible time-dependent deformation in which a material under constant mechanical stress and elevated temperature for a considerably prolonged period of time, starts to undergo permanent deformation. Creep deformation occurs in three stages namely, primary, secondary and tertiary. Out of these three stages, secondary or steady state creep is particularly an area of engineering interest as it has almost a constant creep rate. Creep deformation plays a significant role in understanding effective service life of an engineering component working under high temperature conditions as such components such as super-heater and re-heater tubes and headers in a boiler, jet engines operating at temperature as high as 1200 C, usually experience a failure or rupture due to creep phenomenon. Design engineers keep a close attention on working stress conditions and elevated temperature under which an engineering component is expected to work as these conditions determine the onset of creep behavior in an engineering component. By recognizing the parameters of material response to creep behavior, engineers can analyse the useful service life and hazardous working conditions for an engineering components. Recognizing the creep phenomenon as high temperature design limitation, ASME Boiler and Pressure Vessel Code have provided guidelines on maximum allowable stresses for materials to be used in creep range. One of the criteria for determination of allowable stresses is 1% creep deformation of material in 100,000 h of service. Thus, the study of creep behavior in engineering components pertaining to high stress and temperature working conditions is very important as it affects the reliability and performance of the engineering components. The aim of our study is to understand the behavior of secondary creep deformation so that an advanced reinforced functionally graded material with better creep resistance, can be designed. In this paper, a secondary creep analysis of functionally graded (FG) thick-walled rotating cylinder under internal and external pressure is conducted. The novelty of the model intends to specify secondary creep stresses and strains by employing exponential, linear and quadratic volume reinforcement for ceramic in metal matrix in radial direction. This will help us to understand the effect of volume reinforcement in FG cylinder under internal/external pressure and rotating centrifugal body force by obtaining secondary creep stresses and strains. The response of the FG cylinder with isotropic material is analyzed and the solution for stress–strain rates in radial and tangential directions are obtained in closed form. Comparison of steady state creep stresses and strains under exponential, linear and quadratic volume reinforcement profiles are discussed and presented graphically.

Hygrothermoelastic response of a finite hollow circular cylinder

In this paper, a hollow circular cylinder of finite length with finite extent occupying the space is considered. Based on the hygrothermoelasticity theory, the transient response of a hollow circular cylinder subjected to the hygrothermal loading at the surface is analyzed. The analytical solution for the coupling and uncoupling effects of temperature, moisture, and thermal stresses is obtained by using the integral transform technique. The numerical results of the transient response of the hygrothermoelasticity field are presented graphically for a graphite fiber–reinforced epoxy matrix composite material (T300/5208).

Flow-induced vibrations of elastically-mounted C- and D-section cylinders

We numerically study the flow-induced vibration (FIV) response of an elastically-mounted cylinder in two-dimensional coordinates at Reynolds number of 100. In particular, the effects of shape of frontbody and afterbody are systematically investigated by varying the cylinder’s cross-section, keeping the mass ratio of 5 as constant. The following cross-sections are considered — circular, C-section, inverted D-section, D-section, and inverted C-section. We employ an in-house flow solver based on the sharp-interface immersed boundary method and the solver is one-way coupled with a forced harmonic oscillator equation with a single degree of freedom. We explain the FIV characteristics using displacement amplitude, spectral characteristics of displacement and force signals, and wake modes. Considering a circular cylinder as a baseline case, a modification in the shape of the frontbody from convex to flat to concave causes large amplitude vibrations. A D-section cylinder, which corresponds to the flat frontbody, shows a significant increase in the amplitude for a wide range of reduced velocity compared to the circular cylinder, explained by combined Vortex-induced vibration (VIV) galloping response. By contrast, a variation in the shape of the afterbody from convex to flat to concave results in reducing amplitude, implying VIV suppression. The suppression is explained by the reduction of unsteady pressure forcing during vortex shedding on the cylinder. We discuss wake structures and vortex shedding patterns as a function of reduced velocity for the cylinders and explain these signatures in terms of the respective FIV response. The fundamental insights reported here are potentially helpful for structural health monitoring and energy harvesting applications.

Size-dependent contact mechanics via boundary element analysis

In classical Hertz theory, the peak failure stresses do not occur directly on the contacting area but beneath the surface, thus contradicting a common appearance of failures on the surfaces. In the present work, we examine the frictionless response of an elastic cylinder pressed between two rigid parallel plates under consistent couple stress theory, as an alternative view to that of Hertz. To address this problem, we develop a couple stress boundary element contact formulation to calculate the deformation and stresses in two-dimensional plane strain problems and find a quite different picture of contact stresses. The numerical investigation shows that the location of maximum effective stress may in fact occur directly on the contacting area, depending on the intrinsic length scale parameter l of couple stress elasticity. For failure analysis in this size-dependent couple stress contact theory, new effective-stress measures, which account for couple-stresses, also are defined. Most importantly, due to the role of asperities in contact behavior, this work is relevant to performance of macro-scale components, as well as micro- and nano-sized devices.

Vortex- and Wake-Induced Vibrations of a Circular Cylinder Placed in the Proximity of Two Fixed Cylinders

PurposeThis study aims to understand the vibratory response of a circular cylinder placed in proximity to other fixed bodies.MethodsA circular cylinder model was placed in a circulating water channel and was supported elastically to vibrate in the water. Another two circular cylinders were fixed upstream of the vibrating cylinder. The temporal displacement variations of the vibrating cylinder were measured and processed by a frequency analysis.ResultsWhen the inline spacings were small, two amplitude peaks appeared in the reduced velocity range 3.0–13.0. When the inline spacings were large, the amplitude response showed a single peak.ConclusionFor small inline spacings, the first peak was attributed to high-amplitude vibrations forced by Karman vortex streets shed from the upstream cylinders. The second peak arose from interactions of the wakes of the upstream cylinder with the vibrating cylinder. When the inline spacing increased, the vortex-induced vibrations resembled those of an isolated cylinder.

The effectiveness of helical strakes in suppressing vortex-induced vibration of tandem circular cylinders

Abstract An experiment study of vortex-induced vibration (VIV) of two rigid cylinders equipped with and without helical strakes (pitch of 10.0D and height of 0.15D) in a tandem configuration was investigated at a critical spacing distance of 3.5D. Here, the cylinders were attached to a structural test rig, which would allow them to oscillate in the cross-flow direction only. The oscillation amplitude and frequency data were collected. Accordingly, the results revealed that in the case of the two bare cylinders, the amplitude response of the upstream cylinder was higher compared to the case of single cylinder usage. Furthermore, outcomes obtained confirmed that the helical strakes successfully reduced the oscillation amplitude for the upstream and downstream cylinders both, whereas they were ineffective if merely applied at the downstream cylinder. Hence, it can be concluded that the arrangement of the strakes influences the VIV suppression in the context of two-cylinder cases.

Efficient measurement of hydrodynamic coefficients for vibrating cylinders at supercritical Reynolds numbers

Free-response Vortex-Induced Vibration (VIV) tests were conducted on a 6.233 m long cylinder with a diameter of 0.325 m. The cylinder was allowed to vibrate in the cross-flow direction and towed at Reynolds numbers varying from 200,000 to 700,000. Rather than conducting hundreds of individual tests at discrete values of reduced velocity, the free-response was measured while continuously varying the towing speed in a manner that ensures quasi-steady response. These ‘ramp-tests’ not only yielded response data corresponding to continuously varying reduced velocity, but also yielded observations of the hysteresis effects associated with increasing or decreasing flow speed. The results from the carefully conducted ‘ramp-tests’ are compared with steady towing speed results to confirm their validity. The cylinder’s free-response was controlled by systematically varying the external electro-mechanical damping. Lift and added mass coefficients at supercritical Reynolds numbers were extracted using the known relationships between cylinder response and hydrodynamic loading. Contour plots of lift and added mass coefficients are presented as a function of dimensionless response amplitude and reduced velocity. Stationary cylinder drag coefficients were also efficiently acquired using the ramp testing technique. These results are presented and compared with the VIV amplified drag coefficients.

A method for along-wind vibration control of chimneys by tuning liners

Reinforced concrete chimneys with steel liners are widely used in waste gas discharge of industrial facilities, and guaranteeing their safety performance in harsh environments is important for industries and society. This paper proposes a novel method for the reduction of along-wind vibration in chimneys with liners by tuning the movement of the suspended liners to the response of the outer cylinder, and the conventional rigid supporting platform is replaced by a combination of radial horizontal tuning systems and vertical suspension systems. This ‘tuned liners’ method is applied to a simplified beam-like model that is able to capture the liners/chimney interaction and is validated against a more detailed finite-element shell model. A design method is proposed to obtain parameters of the tuning system that lead to significant reductions of along-wind vibrations whilst satisfying the relative response requirement. A comprehensive study of the structural vibration under stochastic wind actions is performed to demonstrate the effectiveness of the proposed system. The characteristics of the relative vibration of the outer cylinder and the liners are studied. Comparison with conventional TMD solution is conducted to further explore the advantage of the tuned-liners system under stochastic wind actions. The results indicate that the top displacement and acceleration of the outer cylinder are effectively reduced by 62% and 70% with the tuned liners, respectively. A similar performance using a conventional TMD would require an auxiliary vibrating mass that is approximately 300 tons, which is avoided with the proposed tuned liners. Results show that the proposed technique could be effective in the along-wind control of chimneys in multiple directions, even with some unintentional eccentricities.

Correction to: Thermoelastic response of non-simple solid cylinder with variable properties under a continuous line heat source

Correction to: Thermoelastic response of non-simple solid cylinder with variable properties under a continuous line heat source

Vortex-induced vibrations of a one-degree-of-freedom cylinder transitioning from the inline to the crossflow degree of freedom

Vortex-Induced Vibration (VIV) is studied extensively for cases where the oscillations are possible in the direction of flow (IL VIV) or perpendicular to it (CF VIV). In this work, we study VIV for the angles in between and show how the cylinder's response transitions from a purely IL VIV to a purely CF VIV.

Vibrations of Slender Structures Caused by Vortices

Slender cylindrical structures such as overhead transmission lines, skyscrapers, chimneys, risers, and pipelines can experience flow induced vibration (FIV). The vortex vibrations are a type of FIV; they arise because of oscillating forces caused by flow separation and the detachment of vortices. The paper presents a brief overview of experimental research on vortex induced vibration - VIV of short, rigid cylinders elastically supported (with a small aspect ratio). This overview summarizes the basic results of the vortex vibration (VIV) which have been performed in the last five decades. These studies were mainly related to determining the influence of selected parameters - mass, damping and Reynolds number on the cylinder response, either in one direction only or simultaneously in the flow direction and transverse to the flow direction, and with the search for a map of vortex images in the trace (vortex wake pattern map).