Papers by Keyword: Flow-Induced Vibration

Abstract: This research investigated the effect of span length variation and capless prismatic structure on the performance of the micropower generator from flow-induced vibration. The vibration response type covers galloping and vortex-induced vibration regimes. The mini harvester energy induced by the harmonic oscillation of prismatic structure was implemented based on the magnetostrictive principle to gain electricity using a galfenol alloy (Fe-Ga). The power generation variations are influenced by the amplitude, frequency, structure displacement, span length, and shape of the bluff body. The optimum power generation is 2.87 mW, and the maximum power generation is 10.63 mW at the resonance velocity Vr of 6.45. Reducing the frequency characteristics of circular cylinders by applying a cap end tip affect power generation characteristics and galloping behaviour for the prism with a span length of 200 mm but not for other span lengths. The effect of span length variation on free vibration and power generation performance for all prism models is similar in that both features are decreased by increasing span length. However, it enhances onset valued power generation. Power generation is considered for the independent electricity supply for specific sensor or wireless devices of an IoT system.

Abstract: This work is concerned with the modelling of the interaction of fluid flow with flexible solid structures. The fluid flow considered is governed by the incompressible Navier-Stokes equations and modelled with stabilised low order velocity-pressure finite elements. The governing equation of fluid movement is described by an arbitrary Lagrangian-Eulerian (ALE) strategy. The structure is represented by means of an appropriate standard finite element formulation. A simple data transfer strategy based on a finite element type interpolation of the interface degrees of freedom guarantees kinematic consistency and equilibrium of the stresses along the interface. The resulting strongly coupled set of non-linear equations is solved by means of a partitioned solution procedure, which is based on the Newton-Raphson methodology and incorporates the full linearization of the overall incremental problem.

Abstract: Flow-induced vibration occurs widely in flow pipelines, and pipeline vibration signals have various frequency characteristics corresponding to different flow regimes. Therefore, an novel noninvasive approach to flow regime identification for wet gas flow in a horizontal pipeline is presented in this paper. The vibration signals were collected by a transducer installed on external wall of pipeline. Empirical mode decomposition (EMD) was used to decompose the vibration signal into different intrinsic mode functions (IMFs), and then the kurtosis of each IMF component for each experimental data was calculated. Finally, the IMF kurtosis feature vector was input to the support vector machine (SVM) to identify three typical flow regimes for wet gas flow including stratified/stratified wavy flow, annular/annular mist flow and slug flow in a horizontal pipeline 50 mm in diameter. The experimental results show that the proposed approach can identify flow regimes effectively, and the identification rate is 80.6%.

Abstract: The flow-induced micro-vibration in Shuifu County Town near Xiangjia Dam is studied in this paper. First the characteristics of the micro-vibration are investigated based on the in situ measurement, and then the dynamic property of the still basin which is thought to be the vibration source is analyzed with the effect of fluid-structure interaction (FSI) considered. Finally, the reason of the micro-vibration in Shuifu county town is discussed and several possible engineering suggestions for vibration reduction are also proposed.

Abstract: In order to study the flow-induced vibration of the spillway tunnel working gate of one reservoir, hydraulic model test with scale 1:20 was conducted to obtain the dynamic pressure characteristics on the working gate. Experiment modal analysis method was employed to identify the structure dynamic characteristics through the 1:10 working gate mode test. The 3D FEM model of the gate was built to simulate the vibration response of the structure. The research showed the low order modal frequencies of the working gate were not fully breaking away from the high energy zone of the dynamic water, which would induce severe vibration. The vibration response of the gate became the biggest when it was operating at 0.5 partial opening.

Abstract: Flow-induced vibration (FIV) of a head gimbals assembly (HGA) in hard disk drives (HDDs) limits the positioning accuracy of magnetic head in the HGA for higher HDD magnetic recording density. The pressure fluctuations characterize turbulent fluctuations exciting the HGA off-track vibration (HGA-OTV). In this paper, experimental studies have been carried out to investigate the spectrum characteristics correspondence between pressure fluctuations around an HGA and the simultaneous HGA-OTV under different HDD rotation speeds. A practical and effective experimental setup has been implemented to enable the simultaneous measurements on both the pressure fluctuation and HGA-OTV signals, where pressure fluctuations are measured with a pressure transducer through a small hole on the HDD top cover and the direct HGA-OTV signals are detected through a laser Doppler vibrometer. Results under conditions of three different HDD rotation speeds of 7200, 9000, 10800 rpm have been investigated and compared. It is shown that the HGA off-track vibration spectra are highly associated with those of the pressure fluctuations in terms of principal peaks in four frequency bands around 1.8 kHz, 2.5-3.5 kHz, 7-7.5 kHz and 11.5-12.5 kHz. With increasing HDD rotation speed, it is shown that the spectrum magnitudes of both the pressure fluctuation and the HGA off-track vibration increase correspondingly, while the principal peak positions in spectra of either pressure fluctuation or the HGA off-track vibration always hold the line. This study demonstrates a causal nexus from the pressure fluctuation to the HGA off-track vibration and suggests the feasibility of controlling the HGA-OTV through suppression of pressure fluctuations around the HGA.

Abstract: Flow-induced vibration widely exists in fluid power machinery, and there is a great relation between the vibration and engineering construction. In this paper, prototype valve experiment and three-dimensional simulation has been done on the pre-opening sleeve valve. High-frequency minute dynamic pressure sensors are adopted in the valve in experiment. Vibration data with dynamic pressure in different conditions are collected and measured to find out the pulsation characteristics of the valve disc during the experiment. Meanwhile, three-dimensional numerical simulation and analysis on the internal flow field of the valve has carried out, in order to discover the factors of vibration induced by fluid flow. The result shows that the main cause of flow-induced vibration varies in different conditions. At the condition of large opening and large pressure difference between valve inlet and outlet, it is mainly due to vortex-induced vibration. Several ways such as improving damping, avoiding the resonance frequency and changing the type of the valve profile can be taken to weaken the vortex-induced vibration.

Abstract: When a vibration force acts on piezoelectric material, which will deform to-and-from and excite electricity on its polar surfaces. In this paper, the air resonance structure is designed by the principle of air self-oscillation, when the shells are flying with high-speed, the air into the shells will produce self-excited oscillation, the oscillation frequency only relates to the structure of the resonator rather than the speed of the wind which causes the oscillation of piezoelectric ceramics to produce a continuous charge, storage devices are used to store the charge, as regulated, the voltage is used as the power supply circuits of the fuse circuit.

Abstract: Abstract: The section of diversion penstock near the powerhouse behind dam in some hydropower station is equipped with expansion joints, which is used to remedy deformation of penstock in axial and lateral due to the variation of temperature and foundation subsidence. When the hydropower station is in normal water diversion and power generation, the discharged flow generates fluctuating loads, induces structural vibration of guide cylinder of expansion joints, gives rise to cumulative fatigue damage of guide cylinder and also leads to weld joints in guide cylinder cracking to fall off. When generating unit is in the condition of load rejection, expansion joints bears not only the fluctuating pressure loads of the flow, but also undergoes the shock from water-hammer pressure as well, so this demands higher requirement for the safety and reliability of expansion joints structure. It has important engineering value for ensuring safety and reliability of water-diverting power generating system to conduct researches on dynamic effect that fluctuating loads having on expansion joints guide cylinder structure and cumulative fatigue damage of terminal weld of guide cylinder

Abstract: In this paper we conduct study on flow-induced vibration of large-span upwelling radial steel Gate and its hydraulic hoist. Place an emphasis on vibration response characteristics under two working conditions of diversion and drainage, which proves the safety of hydraulic hoist gate vibration caused by gate vibration. Firstly, we study on dynamic characteristics of fluid-structure interaction of association system of gate and start and stop lever, reveals the discipline of the effect fluid having on structural dynamic characteristics. On this basis, flow-induced vibration characteristics under two conditions of with and without start and stop lever action considered. The results indicate that the gate vibration response with hydraulic hoist used decreases, which explains start and stop lever has certain effect of restraining vibration on gate vibration. In addition, under the working condition of drainage the vibration magnitude of start and stop lever is smaller than that of gate body, which explains there is damping action during transference of gate vibration through start and stop lever. The results find out that on the assumption of optimized gate structure and hydraulic arrangement, it is practicable, safe and reliable to adopt hydraulic hoist. The achievement has directive significance on similar projects construction in the future