Flow-induced Vibration Analysis Research Articles

Study for the cross-flow coupling mechanism of tandem cylinder groups at low Reynolds number

A numerical analysis of flow-induced vibrations for tandem cylinder groups which include two and three tandem cylinders with a spacing ratio of L/D = 5.5 (where L is the distance between the circular cylinders and D is the circular diameter) in planar shear flow is carried out. The cylinders can only vibrate freely in the cross-flow direction. A finite element method called four-step semi-implicit characteristic-based split (4-SICBS) is used to solve the Navier-Stokes equation. On the other hand, in order to maximize the oscillation response of the dynamic system, the damping ratio of it is ξ = 0. And the mass ratio of structure is set to mr = 2.0. The four main parameters, such as the number of cylinders (Num = 2, 3), Reynolds number (Re = 100, 160), the shear ratio (k = 0.0, 0.05, 0.1) as well as the reduced velocity (Ur = 3–30) are mainly studied the dynamic behaviors, frequency and spectrum characteristics, phase characteristics as well as energy characteristics of tandem cylinder groups. The results show that vibration responses of the upstream cylinders in tandem cylinder groups are similar to that of a single cylinder, while the parameters play a key role in flow-induced vibrations of the midstream and downstream cylinders. As Re = 100, the downstream cylinder of two tandem cylinders and the midstream cylinder of three tandem cylinders are in the state of increasing and then decreasing, and the downstream cylinder of three tandem cylinders has a larger vibration response with the change of k. As k = 0.1, the amplitude drops to zero with the increase of Ur. In addition, the situation becomes more complicated with the increase of Re. For the downstream cylinder of three tandem cylinders at Re = 160, there are two peaks of the cross-flow amplitude. The oscillation remains strong at larger Ur for the case of k = 0.1. Finally, the interactions between cylinders are revealed, together with the vortex dynamic mechanism underlying the oscillation characteristics of tandem cylinders exposed to planar shear flow.

Thermal hydraulic design and evaluation of the solid microencapsulated fuel in light water reactors

Solid Microencapsulated Fuel (SMF) is a kind of solid fuel rod design that disperses TRISO coated fuel particles directly into a kind of matrix. Without cladding tube and associated failure mechanisms, this type of new fuel design is expected to provide improved performance under normal and even accident conditions. The purpose of this paper is to analyze the thermal hydraulic performance of SMF based on a single channel, compared to the traditional fuel in the 200 MW Nuclear Heating Reactor (NHR200-II). Two kinds of specific SMF by dispersing TRISO particles into Zirconium or SiC matrix were investigated. Thermal margin to DNB was assessed and confirmed by determining the heat transfer capacity under normal condition. Two-phase pressure drop was evaluated by using the homogeneous equilibrium boiling assumption. The centerline temperature of SMF rod was calculated by using effective thermal conductivity of two-phase composite. The analysis of flow instability and flow-induced vibration were also included and compared. This study showed that SMF has a better thermal transfer capacity, a higher margin from vortex shedding and fluid-elastic instability, and a lower fretting wear rate, while a higher sliding wear rate because of a higher Young’s modulus and fundamental frequency, which is compensated by a higher hardness for SiC matrix.

Flow-Induced Vibration and Heat Transfer Analysis for a Novel Hollow Heat Exchanger

A novel hollow shell-and-tube heat exchanger with helical elastic coiled tubes was designed to improve the overall heat transfer performance. Different numbers of helical baffles installed on the hollow helical elastic tubes (HHETs) heat exchanger were compared with the HHET heat exchanger without a baffle. The fluid–solid coupling method was provided to study the effects of the entrance velocity and baffle number on the performances of heat transfer and vibration-enhanced heat transfer. Based on the numerical results, the performances of vibration and heat transfer become more obvious by increasing the entrance velocity. Compared with the HHET heat exchanger without a baffle, adding a baffle or baffles on the HHET heat exchanger can remarkably make the fluid flow more consistent. Whereas a higher number of baffles can weaken the vibration and heat transfer performance of the novel heat exchange, the performance evaluation criteria of the HHET heat exchanger with one baffle, two baffles, and four baffles is improved by 2.04, 4.37, and 2.3%, respectively. It indicates that adding a baffle or baffles to the novel heat exchanger can effectively improve the overall thermal and hydraulic characteristics of the novel heat exchanger.

Mode-based energy transfer analysis of flow-induced vibration of two rigidly coupled tandem cylinders

Two rigidly coupled cylinders are commonly available in engineering practices, which are always subjected to flow-induced vibration (FIV) with large oscillating amplitude due to the complex gap flow. However, their FIV features and the underlying mechanism have not been clearly understanded. In this study, the FIV of two rigidly coupled square cylinders in a tandem arrangement was numerically investigated for Reynolds numbers 100 and 200 and gap L/D = 2.0 and 6.0 in a two-dimensional framework. The dynamic response and flow structures are first studied. Mode-based energy transfer analysis was developed based on proper orthogonal decomposition. The energy transfer between the cylinders and the coherence modes was then analyzed to uncover the underlying mechanism of the FIV. The results reveal that the soft lock-in phenomenon was observed for all cases. When the gap L/D = 2.0, the dynamic response is always smaller than a stationary cylinder and all the wake structures show “2S” modes, which results from the stabilized effects of the upstream cylinder. At L/D = 6.0, the oscillating amplitude is much higher than that of a single square cylinder, due to the vigorous interaction between gap flow and the cylinders. As Reynolds number increased from 100 to 200, both vortex-induced vibration (VIV) and galloping co-exist, while the VIV response was reduced. Concerning the energy transfer, for L/D = 2.0, the first mode pair induced by Karman vortex shedding dominated the wake flow. The primary mode governed by UC stabilized the vibration, while the second mode tended to excite the FIV. For L/D = 6.0 in the galloping branch, the first two modes belonged to the vortex-induced modes, and the third mode represented the galloping mode. The galloping mode tended to excite the flow-induced vibration, while it was contrary for the vortex-induced modes.

Flow-Induced Vibration and Energy-Harvesting Performance Analysis for Parallelized Two Flutter-Mills Considering Span-Wise Plate Deformation with Geometrical Nonlinearity and Three-Dimensional Flow

Recently, micro wind energy harvesting devices such as flutter-mills have received considerable attention. The advantage of a flutter-mill over conventional wind power generators is that it can be easily parallelized. They increase the output power, but exhibit highly complex characteristics because the power generation performance depends on the distance and phase lag of vibration among the flapping sheets. This study reports the modeling and numerical simulations of the flow-induced vibration for two parallelized sheets under uniform flow, by considering the geometrical nonlinearity of sheets and wake shedding from the trailing edge. We modeled the fluid–structure and energy harvesting circuit interaction between two flapping sheets using the unsteady vortex lattice method for fluid and finite element method for the sheets, considering three-dimensional flow and span-wise deformation, to understand the complex interaction between two flapping sheets. The proposed model was verified by evaluating its performance against the results of computational fluid dynamics analyses and existing literature. Additionally, we examined the relationships between the aspect ratio of the sheets, harvested power, and phase lag between two flapping sheets using our model. Moreover, we confirmed the span-wise deformation to appear at a large inlet flow under a large aspect ratio, whereas the phase lag was confirmed to converge during the anti-phase mode when the flapping mode shifted to a higher level. In addition, we modeled the effect of the electrical load in a power generator circuit as the equivalent damping parameter of the sheets. Subsequently, we evaluated the optimal damping parameter of the sheets, which is equivalent to the electrical load in a power generator circuit, to obtain the energy from the fluid, and simultaneously, the phase difference of the flapping sheets converged to the anti-phase. In particular, when the distance between the two sheets is the same as the sheet length, the power generation performance is better than that of the single sheet.

Fluid-structure coupled analysis of flow-induced vibrations in three dimensional elastic hydrofoils

Hydrofoils have been widely used in ocean and offshore structures. The research on their elastic response in turbulent flow is quantitatively challenging, and it is of great interest for consideration in engineering applications. In this study, a fluid-structure coupling numerical simulation of a three-dimensional elastic hydrofoil is performed. The SST (shear stress transfer) k-ω turbulence model is used to simulate the vortex shedding and near-wall flow characteristics with different Reynolds numbers. By coupling the FVM (finite volume method), the elastic response of the hydrofoils is analyzed. Furthermore, the formation and evolution of the trailing vortex is described. The elastic vibration and subsequent stress distribution of the hydrofoil caused by the vortex shedding are investigated. Moreover, the frequency domain characteristics of the vibration and turbulence field are analyzed. The results show that resonance occurs when the frequency of the vortex induced flow field fluctuations matches the natural frequency of the hydrofoil. This leads to intense hydrodynamic fluctuations in the time domain. In addition, the dynamic responses of the hydrofoil will “lock-in” to its natural frequency within a certain range of flow velocities. Although the frequency lock-in is often accompanied by resonance, lock-in phenomena cannot be solely attributed to resonance, which is caused by hydrofoil switching between the free and forced vibration regimes. The frequency lock-in is caused by the dominant frequency modulation induced by the fluid motion, thus, it can exert non-negligible effects on the flow field via fluid-structure coupling.

Analysis and Prediction of Flow-Induced Vibration of Convection Pipe for 200 t/h D Type Gas Boiler

This paper is aimed at the analysis and prediction of the fluid-induced vibration phenomenon in the convection tube bundle area caused by Karman vortex street shedding in the background of a 200 t/h large-capacity D-type gas boiler. Based on the numerical simulation of flue heat state flow field and fast Fourier transform, the lift coefficient curve of different monitoring areas and the corresponding Karman vortex street shedding frequency are obtained. The accuracy of the analysis model is validated by comparing Karman vortex shedding frequency with acoustic equipment standing wave frequency. In order to meet the design requirements of the 200 t/h D-type gas boiler for reliable and stable operation, the vibration characteristics and variation rules of a convection tube bundle in a D-type boiler under different working conditions are predicted.

Analysis of flow-induced vibration of cylinder with splitter plate based on overset grid method

In actual engineering, asymmetric flow often occurs, but rigid partitions are often installed in the direction of the flow field and are symmetric in the flow direction. This will result in a deflection angle between the dividing plate and the direction of the incoming flow. The research results show that when the declination angle is low, the partition plate has a limited impact on the system; when the deflection angle is about 10 degrees, the system vibration characteristics will have abrupt changes, the amplitude will decrease, and the vortex frequency will increase; at the deflection angle 10 degrees to 45 degrees As the declination angle increases, the amplitude increases, and the vortex frequency decreases; it can be seen from the motion trajectory that the declination angle changes suddenly after 10 degrees, and the system has a small amplitude between 10 degrees and 25 degrees. That is, in this declination interval, the partition plate has a better control effect on the vibration of the cylindrical system.

Flow-induced vibration analysis of two unequal-diameter flexible cylinders in staggered configuration from a hydrodynamic force perspective

This paper presents an experimental study on the hydrodynamic features of two unequal-diameter flexible cylinders in staggered arrangement subject to flow-induced vibration (FIV). Five position angles (α = 15°, 30°, 45°, 60°, and 75°) are defined between the tandem (α = 0°) and side-by-side (α = 90°) cases with the centre-to-centre spacing being fixed at P = 6.0d, where d is the diameter of the small cylinder. The time-varying strains obtained from the experimental tests are converted into displacements, and then the hydrodynamic force coefficients of the two cylinders are derived using an inverse analysis method. It is found that the variation trends of the cross-flow (CF) hydrodynamic coefficients with the reduced velocity do not demonstrate qualitative differences from those of their isolated counterparts except in the mode transition regions. The downstream cylinder experiences stronger influence from the upstream cylinder on its CF hydrodynamic characteristics especially at small α. The more frequent mode transitions in the in-line (IL) direction lead to the multi-frequency responses associated with changes in the IL hydrodynamic coefficients. The typical wake-induced flutter (WIF) phenomenon is observed when Vrs = 5.01, 8.77 and 16.28–25.05 for the downstream small cylinder in Case I and α = 75°. The influence of the characteristics of the WIF phenomenon on the hydrodynamic force is evident because of the nonexistence of the high-frequency components in the oscillations.

Prediction of thermohydraulics in shell side of CAP1400 steam generator by two-fluid porous media model

Three-dimensional thermohydraulics in the shell side of the u-tube steam generator are essential for the thermal design and tube flow-induced vibration analysis, which are crucial for the equipment economy and integrity. In this work, the Eulerian two-fluid framework along with porous media model was employed to predict the thermal-hydraulic parameters in the shell side of the CAP1400 steam generator. The two-phase flow in the shell side was treated as flow in porous media with additional momentum and energy source terms for each phase to consider the effects of structure resistance and primary-to-shell heat transfer. The primary side was simplified by the multi-channel model with 16 equivalent tubes. The distributions of thermal-hydraulic parameters for each phase and the mixture phase were obtained. High non-uniformity can be observed for the flow and heat transfer parameters. The ratio between heat released in the hot side and cold side was as large as 2.7. The crossflow energy related to the flow-induced vibration was also derived to find the possible location of tube damage. The most probable location for a potential tube rupture locates at approximate 0.4 rad in the hot side.

Numerical Analysis of Flow-Induced Vibration of Heat Exchanger Tube Bundles Based on Fluid-Structure Coupling Dynamics

Numerical Analysis of Flow-Induced Vibration of Heat Exchanger Tube Bundles Based on Fluid-Structure Coupling Dynamics

Dataset of Flow-Induced Vibrations on a Pipe Conveying Cold Water

Analysis of flow-induced pipe vibrations has been applied in a variety of applications, such as flowrate inference and leak detection. These applications are based on a functional relationship between the vibration features estimated in the pipe walls and the dynamics related to the flow of the substance. The dataset described in this document is comprised of signals acquired using an accelerometer attached to a pipe conveying cold water at specific flowrate values. Tests were carried out under numerals of the ISO 4064-1/2: 2016 standard and were performed in two measurement benches designed for flowmeter calibration, and a total of 80 flowrate values, from 25 L/h to 20,000 L/h, were considered. For each flowrate value, 3 to 6 samples were taken, so that the resulting dataset has a total of 382 signals that contain acceleration values in three axes and a timestamp in microseconds.

A Method Study of Numerical Simulation on Flow Field of Spiral Tube in Steam Generator Shell Side

The lead based fast reactors often use integrated core design scheme, due to its compact structure, and the helical coil tube type once-through steam generators (OTSG) have been utilized in various reactors. In order to study the flow and heat transfer characteristics of the lead bismuth eutectic based coolant in the shell side of the helical coil tube OTSG in lead based fast reactors, a section-by-section solution method is adopted, and the wall heat flux fitting formula is used to simulate the flow field of shell side, with the help of FLUENT software. Finally, the correctness of the section-by-section solution method is verified, the flow and heat transfer characteristics of the shell side are analyzed, and the calculation data of velocity, temperature and pressure field are obtained. Its results lay a foundation for the next step of steam generator flow induced vibration analysis and high temperature stress calculation.

Spectral and statistical analysis of flow-induced vibrations

Spectral and statistical analysis of flow-induced vibrations

Development and verification of hydroelastic model experiment for the flow-induced vibration analysis of roller compacted concrete dam

To carry out the experimental study of flow-induced vibration for roller compacted concrete dam (RCCD), the improved hydroelastic model experiment (HEME) technology that satisfying both the hydraulic and structural dynamic similarities is presented, and an improved combinatorial method is proposed to effectively and accurately calculate the dynamic characteristics of RCCD model under natural excitation and complex environment. Due to the insufficient study on the simulation technique for the interfaces between adjacent concrete layers in RCCD, the conventional HEME technology which is frequently applied is not applicable to the RCCD dynamic analysis. Therefore, the hydroelastic simulation schemes for cold joints and ordinary interfaces in RCCD are firstly presented based on experimental and theoretical researches and numerical verification. Then, the integral RCCD model is established and its dynamic displacements under flood discharge excitation are tested. Furthermore, the proposed method that combines the advantages of natural excitation technique (NExT), singular entropy (SE) method, and eigensystem realization algorithm with data correlation (ERA/DC) method is applied to calculate the dynamic characteristics of RCCD model. The dynamic characteristics of the RCCD model calculated by the proposed theoretical method are very similar to those of the actual RCCD calculated by numerical simulation, which indicate the effectiveness and accuracy for the improved HEME technology and combinatorial method.

A novel methodology for design optimization of heat recovery steam generators with flow-induced vibration analysis

Design of compact, lightweight, and robust heat recovery steam generators (HRSGs) is important for the implementation of offshore bottoming cycles. In this work, a novel methodology integrating flow-induced vibration analysis is proposed for the design optimization of HRSG. The vibration analysis considers four main flow-induced vibration mechanisms, namely turbulent buffeting, vortex shedding, fluidelastic instability, and acoustic resonance. The corresponding sub-models are selected from literature for estimating vibrations of finned tube bundles. The design criteria for vibration are included in the optimization problem as constraints, which affect the decision of the solver simultaneously. The methodology is demonstrated by three cases, in which not only geometric parameters but also operating parameters are set as design variables. With activating vibration constraints, the solver finds appropriate geometric and operating parameters to meet the design requirements. The comparison between the optimizations with and without the vibration constraints shows a trade-off between compactness, lightweight, efficient heat transfer, and the possibility of flow-induced vibration problems. This indicates the importance of consideration of vibration problems when designing such HRSGs.

Flow-Induced Vibration Analysis of Topside Piping at High Pressure

Flow-induced vibration (FIV) from high-velocity multiphase flow is a common source of vibration concern in process piping, potentially leading to fatigue failures and hydrocarbon leaks. A combination of computational fluid dynamics (CFD) and finite element (FE) modeling offers a potentially powerful tool for assessing and diagnosing multi-phase FIV problems in hydrocarbon-production piping systems. Global energy consultancy Xodus Group performed FIV studies on an Equinor-operated topside production system, carrying multiphase flow at high-pressure (approximately 69 bara) conditions, where significant vibration was measured. The study assessed different vibration-simulation methodologies, combining FE analysis with forcing functions based on both correlations and CFD simulations. The aim was to gain a better understanding of the accuracy and limitations of calculation methods typically used to assess fatigue. Calculating Multiphase FIV in Operational Pipework While CFD FIV modeling methods have been well validated against low-pressure water-airflow under laboratory conditions (Emmerson et al. 2016a and 2016b), little has been published to show how well these techniques perform for operational hydrocarbon-production systems. As these systems usually operate at higher pressures with complex, live hydrocarbon fluids and water, the process conditions are often not well defined. They typically incorporate sev-eral features that could complicate the vibration-generation mechanisms such as long upstream pipelines, chokes, and convoluted combinations of pipe bends with complex support arrangements. As part of the development of a new Energy Institute guidance document for subsea pipework, the project with Equinor was instigated following a joint industry project (JIP) established by Xodus, in collaboration with TNO and funded by six major operators, to improve techniques for estimating forcing functions in liquid-gas flows. Vibration measurements were taken at various locations on a section of piping carrying multiphase flow at high-pressure conditions (approximately 69 bara) (Fig. 1). The forces were applied in harmonic, transient, and fluid structural interaction (FSI) simulations (directly coupled FE and CFD). The topside piping arrangement consists of 16-in. schedule-100 piping, with a tee at the top of a riser section followed by six 90° and four 45° 1.5 R/D elbows and is reasonably well supported (as shown in Fig. 1). The measurements provided the vibration velocity of the piping structure, and frequency spectra analysis was performed for comparison with the structural-response simulations. The main locations of interest are V4 and V5 as the measured vibration was the highest here. The peak vibration velocity at V4 is 4.7 mm/s and this occurs at 5.1 Hz in the EW-Y direction (Fig. 2), while at V5 the peak is 6.4 mm/s at 5.2 Hz.

The numerical simulation of the flow distribution and flow-induced vibration analysis for intermediate heat exchanger in a pool-type fast breeder reactor

Intermediate heat exchanger in a pool-type fast breeder reactor transfers heat from the primary sodium to secondary sodium. A dual cell coupling porous media model is used to simulate flow field in both primary and secondary side at the same time. The velocity distribution in the inlet and outlet are also studied in order to find the velocity change of inlet and outlet. Flow-induced vibration is investigated. On the top of primary side outlet, it is easy to occur flow-induced vibration, support plates or baffles need to be installed here to reduce the radial velocity to avoid flow-induced vibration.

Experimental Flow-Induced Vibration Analysis of the Crossflow Past a Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side

Abstract Flow-induced vibration of a single cylinder and two cylinders in tandem and side-by-side configurations is experimentally investigated in this paper in the subcritical regime. The natural frequency of the system varied from 8.8 Hz to 46.2 Hz. The mass ratio, m*, ranged between 158 and 643 while the damping ratio, ζ, between 0.0005 and 0.009. The pairs of cylinders present a spacing ratio of 1.26 (P/D and L/D). In all cases, one and both cylinders (BV) were free to vibrate. Experiments were performed in an aerodynamic channel with a constant height and a variable width, for the evaluation of the influence of the blockage ratio (BR), using accelerometers and hot wire anemometry. The reference velocity, measured at the entrance of the test section was used to calculate the reduced velocity, Vr = U/fnD, with values from 4 to 132 and the Reynolds number between 3 × 103 and 8 × 104. The root-mean-square-values of the displacement amplitudes, Y/D, were obtained through the integration of the acceleration signals. Fourier and continuous wavelets were employed in the analysis. For a single cylinder free to vibrate, the higher amplitudes occur at two distinct reduced velocities, associated with the vibration modes of the cylinder. The vibration amplitude of a single cylinder increased as the blockage ratio increased, decreasing for the highest blockage ratio investigated. For the case of cylinders in tandem, the presence of the fixed cylinder in the wake of the cylinder free to vibrate amplifies the vibration response at high reduced velocities. When the blockage ratio is increased, a sudden increase in the vibration amplitude is observed. When both cylinders are free to vibrate, the relation between the natural frequencies of both cylinders influences the response amplitudes. In the case with two cylinders side-by-side, the vibration amplitude remains similar to a single cylinder, but when both cylinders are free to vibrate, the presence and the influence of flow bistability is observed.

Computational modeling and analysis of flow-induced vibration of an elastic splitter plate using a sharp-interface immersed boundary method

We present the development and benchmarking of an in-house fluid–structure interaction (FSI) solver. An implicit partitioned approach is utilized to couple a sharp-interface immersed boundary method-based flow solver and a finite-element method-based structural solver. In the present work, the coupling is accelerated using a dynamic under-relaxation scheme. The revised coupling is around two to three times faster and numerically stable, as compared to the one that uses a constant under-relaxation parameter. The solver is validated against two FSI benchmarks in which a thin, finite thickness, elastic splitter plate is attached to the lee side of a circular or square rigid cylinder, subjected to laminar flow. In these two-dimensional benchmarks, the flow induces a wave-like deformation in the plate, and it attains a periodic self-sustained oscillation. We employ the FSI solver to analyze the flow-induced vibration (FIV) of the plate in a uniform laminar free-stream flow for a wide range of mass ratio and bending stiffness at Reynolds number (Re) of 100, based on the diameter of the cylinder. At the given Re, two-dimensional numerical simulations show that the FIV of the plate effectively depends only on the mass ratio and bending stiffness. The largest displacement of the plate vibration is found to occur in the lock-in region, where the vortex shedding frequency of the coupled fluid–structure system is close to the natural frequency of the splitter plate. We briefly discuss wake structures and phase plots for different cases of mass ratio and bending stiffness.