Flow-induced Vibration Characteristics Research Articles

Flow-induced vibration of turbo-expander impellers for industrial waste heat recovery: An analysis based on two-way fluid structure interaction

In the effort to conserve energy and reduce emissions, waste heat recovery for power generation offers a significant advantage by enabling energy recycling. The turbo-expander, a critical component within expansion power generation systems, plays a pivotal role. However, flow during various operation can generate vibrations that negatively affect operational efficiency and trigger safety hazards. Therefore, studying the flow-induced vibration of the turbo-expander is of significant value. We apply computational fluid dynamics (CFD) and transient structural mechanics to examine the flow-induced vibration characteristics of the turbo-expander influenced by stator-rotor interaction using a two-way fluid structure interaction (FSI) strategy. The flow field modeling and calculation approach discussed here is validated through actual operating data from a prototype. Subsequent stages involve coupling the steady-state flow field with the structural field and performing pre-stress modal analysis on the impeller. In the end, we integrate flow-induced excitation from flow field calculations with the transient structural field to calculate the impeller’s flow-induced vibration at the expansion end of the turbo-expander. Our analysis reveals that guide vane frequency (3267 Hz), its harmonic frequencies, and pre-stress modal frequency (1465 Hz) prominently manifest in pressure pulsation and the dynamic response of the turbo-expander impeller under the influence of stator-rotor interaction.

Research on the Flow-Induced Vibration of Cylindrical Structures Using Lagrangian-Based Dynamic Mode Decomposition

An oscillating flow past a structure represents a complex, high-dimensional, and nonlinear flow phenomenon, which can lead to the failure of structures due to material fatigue or constraint relaxation. In order to better understand flow-induced vibration (FIV) and coupled flow fields, a numerical simulation of a two-degrees-of-freedom FIV in a cylinder was conducted. Based on the Lagrangian-based dynamic mode decomposition (L-DMD) method, the vorticity field and motion characteristics of a cylinder were decomposed, reconstructed, and predicted. A comparison was made to the traditional Eulerian-based dynamic mode decomposition (E-DMD) method. The research results show that the first-order mode in the stable phase represents the mean flow field, showcasing the slander tail vortex structure during the vortex-shedding period and the average displacement in the in-line direction. The second mode predominantly captures the crossflow displacement, with a frequency of approximately 0.43 Hz, closely matching the corresponding frequency observed in the CFD results. The higher dominant modes mainly capture outward-spreading, smaller-scale vortex structures with detail displacement characteristics. The motion of the cylinder in the in-line direction was accompanied by symmetric vortex structures, while the motion of the cylinder in the crossflow direction was associated with anti-symmetric vortex structures. Additionally, crossflow displacement will cause a symmetrical vortex structure that spreads laterally along the axis behind the cylinder. Finally, when compared with E-DMD, the L-DMD method demonstrates a notable advantage in analyzing the nonlinear characteristics of FIV.

Research on flow induced vibration characteristics of heat transfer tube plugs in nuclear power plant steam generators

Research on flow induced vibration characteristics of heat transfer tube plugs in nuclear power plant steam generators

Effects of Angle of Attack on Flow-Induced Vibration of a D-Section Prism

The VIVACE device, which utilizes flow-induced vibration for harvesting ocean current energy, has been a research hotspot in the field of renewable energy. In this study, the flow-induced vibration characteristics and energy conversion efficiency of a D-section prism were investigated using the k-ω SST turbulence model and Newmark-β method. The vibration amplitude, frequency, equilibrium position offset, and energy conversion efficiency of the two-degree-of-freedom cylinder were systematically analyzed at seven angles of attack between 0 and 180 degrees. The Reynolds number ranged from 368 to 14,742, corresponding to equivalent speeds of 2 to 20. The results indicate that the angle of attack has a significant influence on the flow-induced vibration response of the D-section prism. As the angle of attack changes, the vibration amplitude of the cylinder continuously increases, and the cylinder sequentially enters the vortex-induced vibration, vortex-induced vibration-galloping, and fully galloping branches. The change in the angle of attack disrupts the symmetry of the cylinder’s vibration in the streamwise direction, leading to a shift in the equilibrium position of the cylinder’s vibration. When the angle of attack is 0°, the energy conversion efficiency of the column reaches a maximum of 11.75%. Additionally, at high Reynolds numbers, the vibration of the cylinder is not self-limiting, making it more advantageous for energy conversion devices compared to cylinders with circular cross-sections.

Vibration characteristics and safety analysis of production string in high temperature, high pressure gas wells

During the production of high-temperature, high-pressure (HPHT) gas wells, the gas entering the production tubing column induces vibration, which in turn leads to changes in the mechanical properties and safety of the tubing column. A dynamic model of the production string in an HPHT gas well was established to study the dynamic characteristics of its production string. The additional axial force caused by the transient temperature change and the nonlinear contact collision between the production string and the casing were considered. The Newmark-β method was used to solve the problem by analyzing and comparing the flow-induced vibration characteristics of the production pipe string. In this study, a gas well in the southwest Sichuan Basin was used as the research object to study the effects of gas production, packer setting position, and string wall thickness on the dynamic characteristics of the string. The results show that in the gas production process, intense vibrations are generated in the transverse and longitudinal directions of the tubular column. After high-velocity gas flows through the production tubing column, the vibrations at the wellbore inclination and the top of the tubing column are more intense. With the rise of production and the downward movement of the packer setting position, the vibration displacement and frequency of the tubing column increase. In addition, as the column's wall thickness increases, the column's stiffness rises, which, in turn, reduces the vibration of the column. When the gas production increases from 60 × 104 m3/d to 150 × 104 m3/d, the maximum transverse vibration displacement of the production string will increase by 22.2%–39.3%, while the frequency will increase by 15.3%–54.3%. When the wall thickness of the pipe column reaches 9.53 mm and 10.92 mm, it can be employed to enhance the safety factor of the string and extend the fatigue life of the string. This study provides a theoretical framework for field string protection and production guidance.

Numerical investigation on dynamic characteristics of oil-water annular flow-induced vibration in curved pipes

To improve the stability of water-lubricated transportation and reliability of pipes in service, the fluid–structure interaction numerical model has been established to investigate the dynamic characteristics of oil-water annular flow-induced vibration in curved pipes and the effect of main parameters in this study. The results illustrate that a single vibration mode of curved pipes is excited by oil-water annular flow, and there exists no multi-modality due to the limited pulsation of pressure and interface of two-phase flow. The change of velocities and oil-water ratios leads to change of flow pattern, making the dynamic response severer. When the oil-water ratio is larger than 2.035, its effect is greater than velocity. The physical properties of oil have a significant effect on the dynamic response. The root-mean-square dimensionless displacement AY,RMS/D and maximum dimensionless displacement AY,MAX/D of fuel oil-water annular flow-induced vibration decrease to 75.6% and 76.5% respectively, which means that the increase of dynamic viscosity reduces the fluid force and suppresses the vibration. AY,RMS/D and AY,MAX/D increases by 1.62 times when the bending angle θ increases from 30° to 90°, indicating that the increase of bending angles also leads to the severer dynamic response.

Experimental investigations on flow-induced vibration characteristics of fuel rod with an independent channel for small lead-based reactor

ABSTRACT The technology of nuclear reactors is evolving rapidly, driven by the pursuit of more powerful and efficient systems. The Small Lead-based Reactor (SLR) represents an advanced nuclear reactor design that holds great promise for delivering enhanced power and efficiency. In the context of the SLR’s fuel rod, the high-speed coolant flow within the reactor can induce vibration, potentially causing fretting wear and damage to the cladding. This study utilized the Burgreen correlation to establish an equivalence relationship between water and Lead-Bismuth Eutectic (LBE). An experiment was then conducted to simulate axial flow-induced vibration (FIV) of a simply supported fuel rod, employing an equivalent water loop. Flow-induced vibration characteristics in both the time and frequency domains were investigated at different flow speeds. The experimental results revealed a positive correlation between flow velocity and amplitude. The fuel rod exhibited low-frequency vibrations with a random pattern, registering frequencies around 14 Hz. These experimental findings can be leveraged to enhance the accuracy of numerical simulations for axial flow-induced vibration (FIV) of the fuel rod. Subsequently, the revised numerical model was applied to simulate FIV in the LBE environment using computational fluid dynamics (CFD), and the numerical results were found to be in agreement with the experimental data.

Experimental investigation of flow-induced vibration and flow field characteristics of a flexible triangular cylinder

Flow-induced vibration (FIV) of a flexible cylinder with a triangular cross-section, allowed to oscillate in the cross-flow, inline and torsional direction, is studied experimentally through water tunnel tests. The dynamic response of the cylinder was studied for three different angles of attack ( $0^\circ, 30^\circ, 60^\circ$ ), at reduced velocities of 0.9–16.27, corresponding to Reynolds numbers of 364–3600. At the angle of attack of $0^\circ$ , vortex-induced vibration at low reduced velocity was observed, which transitioned to galloping at higher reduced velocities. At the angles of attack of $30^\circ$ and $60^\circ$ , galloping-type response was observed over the range of the reduced velocities tested. Our results show that the cylinder's torsional oscillation breaks the system's symmetry and affects the structural response at higher reduced velocities regardless of the angle of attack. The FIV response of the flexible triangular cylinder is distinct from that of a rigid flexibly mounted triangular cylinder due to torsional oscillation, spanwise flexibility and the two fixed boundary conditions limiting the amplitude of oscillation. Flow field analysis in the wake of the cylinder was done qualitatively and quantitatively using hydrogen bubble flow visualisation and time-resolved volumetric particle tracking velocimetry techniques, respectively. Our results show the existence of highly three-dimensional vortex structures in the wake of the cylinder. We studied the coupling between the vortex shedding modes in the wake of the cylinder and the structural vibration modes through the spatiotemporal mode analysis using the proper orthogonal decomposition technique to distinguish between different types of the FIV response observed.

Effects of splitter plate and mass ratio on flow-induced vibration and heat transfer characteristics of a circular cylinder in turbulent flow: A numerical study

The two-degree-of-freedom (2DOF) flow-induced vibration (FIV) of a circular cylinder with heat transfer in turbulent flow is numerically investigated. The cylinder with an attached splitter plate is elastically supported and allowed to vibrate in both in-line and transverse directions. The unsteady RANS and energy equations along with the SST k-ω turbulent model are coupled with the equation of vibration to study the FIV of the cylinder. The effects of the attached plate length (L/D = 0.5, 1.0, and 1.5) and the mass ratio (mr=2 and 6.76) on the heat transfer rate, vortex shedding patterns, vibration trajectories, FFT, and cylinder displacements are studied in a wide range of Reynolds number (1156–9246) and reduced velocity (2–16). The results indicate that FIV can have either a positive or negative effect on heat transfer enhancement, depending on the splitter plate length and the type of cylinder vibration response. At high Reynolds numbers, the cylinder vibration response is observed in the galloping region, accompanied by a significant vibration amplitude. In this region, for L = 0.5D, vibration has a positive effect on heat transfer, while for other lengths, this effect is negative. For L = 1.5D and a reduced velocity of 5.5, contributions of vortex-induced vibration (VIV) and surface area in the heat transfer enhancement are 23.5 % and 44.3 %, respectively. By reducing the mass ratio from 6.76 to 2.6 for L = 0.5D, the heat transfer rate increases by approximately 40 % compared to a stationary cylinder.

Flow-induced vibrations of elastically coupled tandem cylinders

We numerically study the transverse flow-induced vibration (FIV) of elastically coupled tandem cylinders at Reynolds number $100$ , using an in-house immersed boundary method-based solver in two-dimensional coordinates. While several previous studies considered tandem cylinders coupled through flow between them, a hitherto unexplored elastic coupling with fluid flow between them significantly influences FIV. We consider a wide range of gap ratio, reduced velocity, an equal mass ratio of both cylinders and zero damping. A systematic comparison between the classic elastically mounted tandem cylinders and elastically coupled cylinders is presented. The latter configuration exhibits two vibration modes, in-phase and out-of-phase, with corresponding natural frequencies approaching the Strouhal frequency of the system. We quantify variation of the following output variables with reduced velocity and gap ratios: cylinders’ displacement; fluid forces; amplitude spectral density of displacement and force signals; phase characteristics; energy harvesting potential; and discuss the wake characteristics using flow separation, pressure distribution, gap flow quantification, and dynamic mode decomposition characterization. The FIV response is classified into several regimes: initial desynchronization with and without gap vortices; final desynchronization; mixed mode; initial branch; lock-in; upper and lower branch; wake-induced vibration; galloping. We draw upon similarities of computed FIV characteristics with those of an isolated cylinder, in which the lower branch exhibits larger a amplitude than the upper branch. The elastically coupled cylinders show a galloping response similar to an isolated D-section cylinder. By invoking the elastic coupling, we demonstrate FIV suppression and augmentation for in-phase and out-of-phase systems. Our calculations show larger energy harvesting potential at reduced cost for elastically coupled cylinders.

Research on the flow-induced vibration characteristics based on heat–fluid–structure coupling in natural gas loop

To research the flow-induced vibration characteristics of the natural gas loop, unsteady numerical simulation is carried out on the loop calculation model under different ambient temperatures and different flow rates, and the influence of different flow rates on the dynamic characteristics of the flow field and its induced vibration characteristics is obtained. The results show that the inherent frequency of the natural gas loop increases slightly under the action of heat–fluid–solid coupling. The maximum equivalent stress of the loop increases with the increase in ambient temperature under low flow conditions, but it is almost constant under high flow conditions. The smaller the cross-sectional area of the loop pipeline inlet, the greater the pressure, and the more significant the pressure gradient along the flow direction. The pressure pulsation of monitoring points in the pipeline under different flow rates presents different rules, and the pulsation amplitude of pipes with different diameters is different, among which the amplitude of the pipe with a diameter of 250 mm is the largest and that of the pipe with a diameter of 150 mm is the smallest. The pressure pulsation signals are concentrated in the low-frequency band of 0–10 Hz, and the range of the band decreases with the increase in the flow rate. The vibration frequency of the loop structure is close to the fluid pressure pulsation frequency and the inherent frequency under the action of heat–fluid–solid coupling, which causes a resonance of about 2 Hz.

Study on Flow-induced Vibration Characteristics of 2-DOF Hydrofoil Based on Fluid-Structure Coupling Method

Study on Flow-induced Vibration Characteristics of 2-DOF Hydrofoil Based on Fluid-Structure Coupling Method

Flow-induced vibration and heat transfer in a cluster of three staggered cylinders with different angles of incidence

A two-dimensional numerical study is performed to explore the synergistic effects of the angle of incidence, gap ratio, and reduced velocity on the flow-induced vibration (FIV) and heat transfer characteristics in a cluster of three staggered, unequal-diameter cylinders. Three distinct angles of incidence (θ = 0°, 15°, 30°) and three gap ratios (G* = 2, 4, 6) are meticulously examined to observe the effect of wake interference on the oscillation amplitude and heat transfer of downstream cylinders by considering forced convection. The investigation encompassed a Reynolds number (Re) of 100, a Prandtl number (Pr) of 0.7, reduced velocity (Ur) ranges from 2 to 20, and a fixed mass ratio (m*) of 2. A user-defined function (UDF) is employed in the Fluent solver to model the cylinder vibration. The findings revealed a captivating pattern: as the gap between the cylinders increased, the oscillation amplitude of the downstream cylinders significantly diminished while simultaneously witnessing a surge in the Nusselt number (Nu). Similarly, a remarkable escalation in both amplitude and Nu is observed when the angle of incidence is increased from θ = 0° to θ = 15° across all the gap ratios. However, for G* = 6 and θ = 30° a reverse trend emerged, characterized by a notable decline in oscillation amplitude up to 32.25% and an exponential rise in the Nu up to 53.74%. Intriguingly, it is further discerned that augmenting θ and G* exerted no discernible influence on the oscillation amplitude and Nu of the downstream cylinder, as it functioned autonomously as a single isolated cylinder.

Experimental Analysis of Flow Induced Vibrations in Heat Exchanger Tube Bundles with P/D of 1.54 Subjected to Crossflow

This paper presents an experimental analysis of flow-induced vibrations in a heat exchanger tube bundle subjected to crossflow. The study focuses on the characterization and insights gained from the investigation. The tube bundle configuration consists of plain tubes with a single flexible tube, arranged in a squared pattern. The primary objective is to assess the flow-induced vibration behavior and identify any potential instabilities within the system. To analyze the flow-induced vibrations, various parameters were considered, including the P/D ratio (tube pitch to tube diameter ratio), which was found to be 1.54. The experiments were conducted under different flow velocities, and the vibration responses of the tube bundle were measured using suitable sensors. The results revealed that the third row of tubes in the bundle exhibited the highest level of instability compared to the other rows. This finding suggests that the positioning of the tubes within the bundle significantly influences the flow-induced vibrations. The vibrations were observed to vary with the flow velocity, indicating a strong fluid-structure interaction. It can be concluded that the squared arrangement of tubes in the tube bundle, along with the specific P/D ratio, contributes to the flow induced vibration characteristics. Understanding these effects is crucial for optimizing the design and operation of heat exchanger systems, as excessive vibrations can lead to mechanical failures and reduced heat transfer efficiency.

Characteristics of Flow-Induced Vibration of Conveying Pipes for Water and Coolant Flow

One of the effects of vibrations resulting from the flow of fluids is the failure that occurs to the structure of the systems, which in turn affects the efficiency of the parts that make up those systems. for the purpose of studying the possibility of improving the performance of the systems, a liquid other than water and coolant (super antifriz\petrol ofisi) was chosen because of its advantages that can be taken advantage of, including the high viscosity of water and its tolerance to high temperatures resulting from combustion or air temperature, as well as low temperatures to ensure the operation of the system, that is, it maintains stability system temperature to obtain the best possible condition In addition to the purity of the liquid from salts and the presence of a percentage of oil in the composition of the coolant, an insulating layer is formed inside the pipes to prevent rust and corrosion in the pipes, thus ensuring the flow of fluids and prolonging the life of the pipes. The aim is to study and analyze the effect of induced vibrations and internal pressure on fluid transport pipes, and to compare them in the cases of using water and coolant under the same conditions. An empirical analysis considering the natural frequencies produced by the effect of fluid pressure under various stabilization conditions. It was observed from the results that the higher the pressure, the greater the percentage of the deflection of the copper tubes compared to the Aluminium tubes when using both liquids (water and coolant) at the same boundary condition noted the percentage of the deflection difference when using copper pipe (from 0% to 20.3%) was less than using Aluminium (from 2% to 59%) when the pressure was increased. That mean the Aluminium pipe better than copper pipe.

Robust CNN-based flow pattern identification for horizontal gas-liquid pipe flow using flow-induced vibration

Determination of flow patterns is crucial for the prediction of unsteady flow parameters, which is important for multiphase flow pipeline integrity management. Thus far, various methods have been put forward, however, their robustness has yet to be thoroughly tested across varying environments. Despite recent progress in flow-induced vibration (FIV) of multiphase flows, variability due to measurement approach and pipeline conditions remains an under-investigated area. This paper proposes a non-intrusive, robust convolutional neural network (CNN) flow pattern identification method based on FIV analysis. FIV for horizontal gas–liquid pipe flow under various flow patterns is investigated experimentally by simultaneously analyzing acquired FIV signals and high-speed video. A range of pipeline scenarios is thoroughly studied, encompassing variations in flow conditions, measurement axes, pipe material, and installation conditions. Both Hilbert-Huang Transform (HHT) and Short Time Fourier Transform (STFT) are used to investigate the characteristics of FIV. The results show distinct flow patterns with the FIV signal varying with measurement axes and pipe conditions. Three processes are applied to increase identification robustness: HHT images to eliminate variability due to structure signatures and flow conditions; Ostu’s threshold to eliminate image magnitude difference; and data augmentation, applied to both time signals and images, to increase database diversity. From these, the morphological features associated with flow patterns are extracted. Pattern identification results using a neural network architecture trained by GoogLeNet show over 95% accuracy. To test the generalizability of the proposed flow pattern identification method, the trained method is employed to make predictions in various pipeline scenarios. The results show that the trained model attains an accuracy of over 90% when predicting the flow pattern using data from different axes, and an accuracy above 80% when predicting with different pipe material and installation conditions. During the model training phase, the integration of multiple databases or the implementation of transfer learning can result in a substantial improvement in accuracy, reaching a respectable level of at least 90%.

Flow-Induced Vibration Hybrid Modeling Method and Dynamic Characteristics of U-Section Rubber Outer Windshield System of High-Speed Trains

The flow-induced vibration characteristic of the U-section rubber outer windshield structure of high-speed train is the key factor to limit its high-speed movement. Accurate and effective flow-induced vibration analysis of windshield structures is an important topic. In this paper, a hybrid modeling method for the analysis of flow-induced vibration of windshield structure is innovatively proposed for the U-section rubber windshield system of high-speed train. The method uses the external aerodynamic load obtained by aerodynamic simulation as the input condition of the flow-induced vibration model, and maps the aerodynamic load to the structural dynamics model characterized by the modal test data of the windshield structure. The flow-induced vibration model is established by means of modal superposition method and the time-domain response is effectively integrated by Runge Kutta method with variable step size. The results show that this method can effectively simulate the flow induced vibration of the wind baffle structure, and the real-time relationship between the aerodynamic load and the modal characteristics of the structure and the response of displacement and velocity can be obtained. On this basis, the comprehensive dynamic performance of the windshield system of high-speed trains at 400 km/h under external aerodynamic load is studied, that is, the force, displacement and velocity variation rules of the flexible structure are examined. It is determined that the displacement and velocity response curve of the measuring point near the lower side of the U-section rubber outer windshield is significantly higher than that of other parts. Moreover, the contribution of the first mode to the dynamic response of the structure is very obvious. This method provides an efficient calculation method for analyzing the flow-induced vibration characteristics of complex flexible structures.

Coupling performance of two tandem and side-by-side inverted piezoelectric flags in an oscillating flow

The flow-induced vibration characteristics and energy extraction performance of two flexible inverted piezoelectric flags arranged in tandem and side-by-side configurations in an oscillating flow are studied. An immersed boundary-lattice Boltzmann method is employed for Reynolds number of 100, mass ratio of 2.9 and non-dimensional bending stiffness of 0.26 which correspond to the maximum flapping amplitude for a single inverted flag in a uniform flow. 2D simulations are conducted by varying the ratio R of the frequency of the oscillating flow to the fundamental natural frequency of the flag and the horizontal velocity amplitude (Au) of the flow. Three coupling regimes at Au=0.5 are identified for both tandem and side-by-side flags: chaotic oscillations regime I (0.1≤R≤1), large periodic and symmetric oscillation regime IIa1.1≤R≤1.5andIIb(2.1≤R≤3.0), and small periodic and asymmetric oscillation regime III(1.6≤R≤2). The maximum mean electrical power coefficient C¯P occurs in regime IIa at R=1.5 with, α (piezo-mechanical coupling parameter) = 0.5, and β (piezo-electric tuning parameter) = 1.5. C¯P is 0.1 for a tandem upstream flag, 0.068 for the tandem downstream flag and 0.1 for both side-by-side flags, and is respectively 120%, 300% and 213%, higher than that of the corresponding flag in the uniform flow. This improvement is attributed to the higher flapping angular amplitude (180°), the higher ratio of the flapping frequency of the flags to the oscillating frequency of the flow (virtually constant at 0.5), and constructive vortex interaction in regime IIa.

Numerical investigation on flow-induced vibrations of two tandem cylinders localized selective roughness with different natural frequencies

The characteristics of flow-induced vibrations (FIVs) of two tandem rough cylinders with different natural frequencies transversely to the flow direction are computationally investigated using two-dimensional Unsteady Reynolds-Averaged Navier-Stokes (2-D URANS) equations. Seven different sets of natural frequency ratios fn* between upstream and downstream cylinders (fn*= fn,u/fn,d =0.5, 0.707, 0.866, 1.0, 1.155, 1.414, and 2.0) are performed in the range of 30,000≤Re≤120,000, where fn,u and fn,d are the natural frequencies of the upstream and downstream cylinders, respectively. The spacing ratio is d/D=2.57 (where d is the center-to-center longitudinal spacing between two cylinders and D is the diameter). The mass ratio is m*=1.343. The characteristics of amplitude response and frequency response are analyzed in detail. According to the frequency response of the two cylinders with different natural frequency ratios, three main interactive oscillating patterns of the downstream cylinder are observed: (1) Forced oscillating pattern: the downstream cylinder oscillates forcedly with the upstream cylinder, and the dominant oscillating frequency of the downstream cylinder is equal to that of the upstream cylinder. (2) Independent oscillating pattern: the downstream cylinder oscillates independently with its own natural frequency. (3) Beat oscillating pattern: the downstream cylinder oscillates with two dominant frequencies, one is equal to the oscillating frequency of the upstream cylinder, and the other one is equal to its own natural frequency. The different natural frequencies of the cylinders suppress the vibration of the downstream cylinder at different reduced velocity ranges. The displacement time history, frequency spectrum, and vortex structures of each oscillating pattern case are also analyzed for elucidation.

Numerical study on flow-induced vibration of LBE-cooled wire-wrapped rod bundle

Flow-induced vibration (FIV) characteristics of LBE-cooled wire-wrapped rod bundle are crucial to the wire-to-cladding fretting. In the present study, numerical simulation on FIV of wire-wrapped rod bundle in LBE flow was performed using a fluid–structure interaction methodology based on the coupling between fluid and solid domains. The effects of geometry parameters on the FIV of wire-wrapped single rod and rod bundle were obtained. The results show that the circumferential force of coolant on the single fuel rod was uneven, which made the fuel rod undergo elliptical and off-axis periodic vibration. The variations of structure parameters of wire spacers had weak effects on the vibration of the single rod, while significant effects on the vibration trajectory of rod bundle. The vibration characteristics of border rods were more sensitive to the variations of transverse flow, while the center fuel rods were more sensitive to the difference in support constraint.