Flow-induced Vibration Analysis Research Articles

Flow-Induced Vibration Analysis by Simulating a High-Speed Train Pantograph

This paper investigates the aerodynamic behavior and dynamic characteristics of high-speed train pantographs under various operating conditions using advanced aerodynamic simulations and dynamic analyses. The simulations show significant fluctuations in aerodynamic loads during tunnel entry and exit, heavily influenced by train speed and pantograph position (raised/lowered). Modal simulations reveal distinct low-frequency vibrations in pantographs, significantly impacted by external aerodynamic forces. Importantly, the lowered position exposes the pantograph to upward aerodynamic forces, leading to increased bow-net contact force and off-line rate, ultimately compromising current collection stability. Both maximum contact force and off-line rate further increase with higher train speeds. To improve pantograph design, the paper proposes adjustments to the airbag’s equivalent spring stiffness and the bow head’s density. These modifications aim to mitigate contact force and enhance the stability and reliability of pantographs at high speeds. This research offers theoretical and practical insights, aiding in the design, optimization, and refinement of future pantograph systems.

Numerical Analysis of Flow-Induced Transverse Vibration of a Cylinder with Cubic Non-Linear Stiffness at High Reynolds Numbers

Numerical calculations were performed to study the vortex-induced vibration (VIV) of a circular cylinder, which was elastically supported by springs of linear and cubic terms. These simulations were conducted at high Reynolds numbers ranging from 4200 to 42,000. To simulate the cylinder’s motion and the associated aerodynamic forces, Computational Fluid Dynamics were employed in conjunction with dynamic mesh capabilities. The numerical method was initially verified by testing it with various grid resolutions and time steps, and subsequently, it was validated using experimental data. The response of cubic nonlinearities was investigated using insights gained from a conventional linear vortex-induced vibration (VIV) system. This 2D study revealed that both the amplitude and frequency of vibrations are contingent on the flow velocity. The highest output was achieved within the frequency lock-in region, where internal resonance occurs. In the case of a hardening spring, the beating response was observed from the lower end of the initial branch to the upper end of the initial branch. The response displacement amplitude obtained for the linear spring case was 27 mm, whereas in the cubic nonlinear case, the value was 31.8 mm. More importantly, the results indicate that the inclusion of nonlinear springs can substantially extend the range of wind velocities in which significant energy extraction through vortex-induced vibration (VIV) is achievable.

Hybrid Method for Large Diameter Spool Vortex-Induced and Flow-Induced Vibration Analysis

Hybrid Method for Large Diameter Spool Vortex-Induced and Flow-Induced Vibration Analysis

Flow-induced vibration analysis in a pump-turbine runner under transient operating conditions

The dynamic characteristics of the pumped storage unit (pump-turbine runner) make it highly susceptible to vibrations. Previous studies seldom addressed the clearance variation due to runner vibration, largely because of two challenges: the integration of the moving grid with the clearance and governing equations, and the intricacy of factoring in the entire shaft system's influence on vibration. By employing user-defined functions (UDF), kinematic equations for the pump-turbine runner's rotation and translation were formulated and integrated with computational fluid dynamics results. This paper introduces a computational method to simulate clearance-induced vibration displacement. The study examines the impact of clearance vibration displacement on the pump-turbine's transient flow field and runner vibrations under various operating conditions. Notably, deviations from the rated load condition led to an expansion-contraction trajectory of the runner axis, culminating in chaotic behaviour in the "S" characteristic zone. The correlation between runner vibrations and pressure fluctuations strengthened with the clearance displacement model, especially in narrow labyrinth seal clearances. Simulations also provided a refined estimation of the secondary rotational speed increase during load rejection. The method's reliability is confirmed through field test data comparison, offering a fresh perspective to identify the vibration characteristics of the pump-turbine runner.

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.

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.

Analysis of Flow-induced Vibration Based on Discharge Pipeline on Offshore Platform

Objective: Because of the widespread use of offshore oil production platforms, there is a large amount of pipeline equipment on them. The excitation generated by fluid flow in the pipeline will cause flow-induced vibration of the pipeline and damage the pipeline structure. As a result, researching the flow-induced vibration of the pipeline is critical. Methods: In this paper, the pipeline on an offshore oil production platform in the South China Sea is taken as the research object, and the calculation and analysis of the pipeline section on the platform are focused on. The fluid-structure coupling method is used to calculate and analyze the pipeline section, and the flow-induced vibration of the pipeline is simulated. Results: Through calculation and analysis, the results show that the vibration speed of the pipeline in its original state exceeds the specified range. To reduce the degree of vibration, the pipeline constraint is redesigned and flow-induced vibration analysis is conducted. The results show that the vibration level meets the requirements. Conclusion: The flow-induced vibration of offshore pipelines is mainly caused by the uneven distribution of pressure in the pipelines caused by gas-liquid two-phase flow in the pipelines, and the reasonable setting of pipeline constraints can effectively reduce the degree of pipeline vibration.

Analysis of Flow-Induced Vibrations in a Heat Exchanger Tube Bundle Subjected to Variable Tube Flow Velocity

Analysis of Flow-Induced Vibrations in a Heat Exchanger Tube Bundle Subjected to Variable Tube Flow Velocity

Analysis of flow-induced vibration of wire-wrapped fuel assemblies under the liquid metal axial flow in the Gen-IV nuclear reactor

Fluid excitation force is the root cause of flow-induced vibration in the fast reactor core, which is an important cause of nuclear fuel failure and breakage phenomena. In this study, the fluid–structure interaction (FSI) of a filament-wound rod bundles consisting of seven rods in a lead–bismuth fast reactor was simulated. And the fluctuation of fluid excitation force, as well as the vibration displacement and vibration frequency of fuel rods were calculated. It was found that when the fluid flow through the winding wire, the turbulence intensity increases significantly and pressure difference appear on the winding wire windward and leeward surface, which leads to fluctuation in the fluid force, which is the root cause of the emergence of flow-induced vibration. In this structural model, the vibration eventually reach a stable amplitude as well as position, and no pin-to-pin contact occurs.

Numerical Analysis of Flow-Induced Vibration and Noise Generation in a Variable Cross-Section Channel

Numerical Analysis of Flow-Induced Vibration and Noise Generation in a Variable Cross-Section Channel

Theoretical analysis and simulation calculation of hydrodynamic pressure pulsation effect and flow induced vibration response of radial gate structure

This work aims to explore the characteristics of stochastic fluctuant water pressure acted on the surface of large radial gate, and to investigate the flow-induced vibration response of the whole radial gate structure. The finite element calculation model structure of the radial gate is established by taking a large-scale radial gate as prototype to discuss the hydrodynamic pressure acting on the gate leaf with different opening, analyze the dynamic pressure time curves, and achieve the flow-induced vibration response by deeming hydrodynamic pressure as dynamic load. When taking 10% opening of the radial gate, the results indicate that the hydrodynamic pressure distributed on the arc surface of the radial gate changes with the flow conditions, with the maximum pressure occurred at the center of the lower edge of the gate leaf. One point in the time history curve of fluctuating water pressure can be taken as the dynamic load for the flow-induced vibration analysis. The flow-induced vibration responses at the monitoring point of the radial gate structure show periodic changes in the X, Y, and Z directions. The finite element simulation results agree well with the theoretical calculation results, so reference can be provided for the hydrodynamic pressure testing and the flow-induced vibration response calculations.

Sodium Fast Reactor Steam Generator Heat Exchanger Modal Analysis and Additional Mass Coefficient Calculation

The heat transfer tube of the steam generator (SG) of the sodium fast reactor (SFR) isolates the primary sodium from the secondary side water, whose integrity is very important for the safe operation of the reactor. Modal analysis is the key to engineering design. Three design criteria of GB/T151, ASME, and TEMA are adopted for calculation. Based on ANSYS finite element simulation, modal analysis of heat transfer tubes and additional mass coefficient of the liquid sodium flow field is calculated, which is verified by experiments. The results show that GB/T151 is most suitable for calculating the frequency of heat transfer tubes of the SFR steam generator. The numerical model and analysis method established in this paper can accurately carry out modal analysis and additional mass coefficient calculation of non-equal span tube-plate multi-support heat transfer tubes in different media, which lays a foundation for flow-induced vibration analysis of SFR heat exchanger equipment.

Numerical Analysis of Flow-Induced Vibration of Deep-Hole Plane Steel Gate in Partial Opening Operation

Hydraulic steel gates are the core adjustment mechanism for water conservancy projects, the safety of which is related to the safety of the entire water conservancy project. In this study, the issue of flow-induced vibration under the influence of pulsing water pressure when the deep-hole plane steel gate construction is partially opened is investigated using a numerical calculation approach of CFD–CSD coupling. The time-history pulsating pressure loads of each part are first determined by tracking the upstream, bottom, and downstream pulsating water pressure loads under partially open operation conditions of the gate. The impact of the water in front of the gate on the natural vibration mode and frequency of the gate is then investigated based on the analysis of the dry/wet modes of the gate structure. Additionally, the hydrodynamic load is applied to the finite element model of the gate structure while taking into account the fluid–structure coupling effect, and the results of the gate flow-induced vibration response are obtained. Three typical local opening relative openings are chosen, with the operating state of the design water head (Hs = 70 m) of a deep-hole plane steel gate as an example. According to the analysis’s findings, the gate’s natural vibration frequency is greatly lowered under the influence of the water in front of it, and its amplitude increases by 50%. The pressure value pressing on the gate changes dynamically as it is partially opened and discharged. The maximum dynamic displacement value and the maximum dynamic stress value of the gate both appear in the middle and lower part of the gate under the condition of partial opening, and both occur when the relative opening is e/H = 0.125. The maximum displacement value is 3.43 mm, and the maximum stress value is 161 MPa. The maximum dynamic displacement and dynamic stress of each gate component steadily decrease with an increase in the relative openness. The gate dynamic response analysis approach described in this research can serve as a guide for hydraulic engineering design.

Nonlinear vortex dynamic analysis of flow-induced vibration of a flexible splitter plate attached to a square cylinder

Flow-induced vibration (FIV) of a flexible splitter plate attached to a square cylinder in laminar flow is investigated using a two-way fluid-structure interaction (FSI) simulation. The Reynolds number based on the edge length of the square cylinder is fixed at Re = 332.6. Numerical results show that the vortex structure falling off on both sides of the square cylinder will excite the vibration of the flexible plate. There is a noticeable phase difference between the flexible plate's hydrodynamic load (lift) and the vertical vibration displacement of the end of the plate. It is also found that there is a pronounced hysteresis effect on the vortex shedding on both sides of the square cylinder due to the action of the flexible plate. The viscous dissipation term dominates the vorticity transport in low Reynolds number flow regimes. The viscous dissipation term reflects the flow trend of the flow field to a certain extent. The results obtained are insightful to the design of FSI-based ocean engineering structures using flexible plates.

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

According to the needs generated by the industry, there is an urgent need to investigate the flow vibration response law of the elastic tube bundle of heat exchangers subjected to the coupling effect of shell and tube domain at different inlet flow velocities. In this paper, based on the continuity equation, momentum equation, turbulence model, and dynamic grid technology, the vibration response of the elastic tube bundle under the mutual induction of shell and tube fluids is studied by using pressure-velocity solver and two-way fluid-structure coupling (FSC) method. The results show that the monitoring points on the same connection block have the same vibration frequency, while the vibration amplitude is different. Monitoring point A is the most deformed by the impact of fluid in the shell and tube domain. When the inlet velocity( v shell = v tube = 0.15 , 0.4, 0.5 m/s) of shell and tube is low, the amplitude of tube bundle vibration in the Y direction is greater than that in X and Z direction, and the tube bundle produces periodic vibration in the vertical direction. The vibration equilibrium position of the tube bundle along the shell flow direction gradually moves up with the increase of the inlet velocity. The amplitude in the Y -direction of the elastic bundle decreases with the increase of shell-side and tube-side velocity. The relationship between the vibration amplitude in the Y direction and the entrance velocity is a linear function.

Flow-induced vibration analysis of a prototype pump-turbine runner during turbine start-stop transient process

Recently more start-stops per day of the pump-turbine units are required by the power grid for load regulation. During the turbine start-up and shut-down transient processes, the flow and pressure of the prototype pump-turbine change dramatically at different guide vane opening angles. The extremely unsteady pressure fluctuation in the flow passages can induce large deformation, stress concentration, and strong vibration of the pump-turbine runner. Therefore, it is significantly important to study the unsteady flow characteristics and the corresponding flow-Induced vibration of the runner during turbine start-up and shut-down transient process. In this investigation, a 3D model of the pump-turbine unit including the flow passages of the spiral casing, stay vane, guide vane, runner, and draft tube, crown chamber, band chamber, labyrinth seals, and balance pipes are constructed. The flow characteristics of the unit during the turbine start-up and shut-down process were analysed by coupling the 1D pipeline calculation and 3D turbine flow domain calculation. By mapping the pressure distribution of the fluid domain to the runner structure domain, the flow-induced dynamic behavior of the pump-turbine runner is performed, and the large deformation and stress concentration of the runner are investigated in detail. The flow-induced vibration results achieved are able to provide meaningful suggestions for safe operation and for improving the pump-turbine runner design.

CFD-FEM Analysis of Flow-Induced Vibrations in Waterjet Propulsion Unit

This paper investigates the problem of vibration in an axial flow waterjet propeller with high power density and low specific speed. Based on fluid–structure coupling vibration analysis, combined with modal analysis and ship tests, the unsteady fluid–structure coupling of a waterjet propeller is examined, and the vibration characteristics of the propeller under different speed conditions are studied. The results show that the vibrations of the waterjet propeller mainly come from the frequency response of the rotor and the structural resonance response. The frequency distribution characteristics and amplitude intensity are observed to increase with increasing rotation speed. The variations in the propeller vibration characteristics, with respect to parameter changes, are analyzed at different gap spacings between the rotor and stator, allowing the variation law of vibration intensity with rotor stator spacing to be obtained.

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.