Flow-induced Vibration Analysis Research Articles

Flow-induced vibration analysis of nuclear fuel rods using equivalent fuel element model

This research investigates the Flow-Induced Vibration (FIV) of a fuel rod within a fuel assembly using a novel technique to reduce the computational cost. In partitioned Fluid-Structure Interaction (FSI) problems, in high-density fluids because of strong interaction between the fluid and the structure, fulfilling the boundary conditions is likely to fail due to oscillatory convergence or even divergence, and especially shell geometry exacerbates the situation. Either ramping or Under-Relaxation (UR) or both will help avoid the failure but instead leads to additional numbers of coupling iteration, and therefore repeatedly solution ofsolvers. As a novelty, an equivalent (EQ) rod model is introduced to simplify modeling of a fuel rod’s complex geometry. The model makes under-relaxation and ramping algorithms unnecessary, or at least lessens the number of the Supplementary Coupling Iterations (SCI).To prove this, three benchmark problems have been investigated. The first one studies theFIV of a brass rod in anannularduct and the second one studies the FIV ofa shell bundle exposed to axial flow. Finally, the modal characteristics of a typical fuel rod is determined. Results reveal that EQ rod is applicable to boiling water reactors and pressurized water reactors although for fluids much denser than water as it is in heavyliquidmetal cooled reactors, the results are slightly different.

VIBRATION ANALYSIS OF A NANOTUBE SUPPLIED WITH FLUID IN SOME DIFFERENT BOUNDARY

vibration modeling of carbon nanotubes comes with nonlinear equations which are difficult to solve exactly and analytically with any existing general analytical method. However, in many cases of developing symbolic solutions for the nonlinear equations, recourse is made to approximate analytical methods in which their accuracies largely depend on the number of terms included in the solutions. In this work, analytical solutions are presented using differential transformation method with after-treatment technique for nonlinear analysis of vibration and flow-induced vibration of fluid-conveying carbon nanotube resting on Winkler and Pasternak foundations. The developed analytical solutions are used to investigate the effects of nonlocal parameter, Knudsen number, temperature, foundation parameters and boundary conditions on the dynamic behaviour of the single-walled nanotube. Also, the developed analytical solutions are verified with the numerical solutions and validated with experimental results. Good agreements are established between the results of the analytical solutions and the numerical solutions, and also between the results of the analytical solutions and the experimental results. The analytical solutions as presented in this work can serve as benchmarks for other methods of solutions of the problem. They can also provide a starting point for a better understanding of the relationship between the physical quantities of the problems.

Numerical study of flow-induced vibration of fuel rods

In this work, Fluid-Structure Interaction (FSI) simulations are performed to study Flow Induced Vibrations (FIV) of nuclear fuel rods using the commercial code STAR-CCM+. The Navier-Stokes equations are solved on deforming grids with the Arbitrary Eulerian-Lagrangian (ALE) formulation. The finite element method is used to solve the linear elastic problem for the structure. The two solvers are tightly coupled together with the Gauss-Seidel method to solve the FSI problem. The first part of the work focuses on the FIV of a single rod. Two types of rods are considered: 1) a bare rod and 2) a rod with a wire spacer helically wrapped around its external surface. For the case of the bare rod configuration, the effects of the working fluid on the dynamics is investigated and a correlation for the frequencies as function of density is proposed. The second part of the work focuses on the analysis of FIV for two different configurations of bare seven-rod bundle. One of the main features of the considered configurations is the appearance of axial flow fluctuations in the rod gaps due to the velocity difference in the sub-channels between the rods. Therefore, this part of the work focuses on the study of the effect of the velocity pulsations on the vibrations of the rods.

Flexoelectric and surface effects on size-dependent flow-induced vibration and instability analysis of fluid-conveying nanotubes based on flexoelectricity beam model

Fluid-conveying micro/nano tubes are key tools, which have great applications in biological devices and especially smart drug delivery in order to target the cancer cells. Furthermore, exploiting the smart materials and their combination with drug delivery systems may positively affect the instability control and improve the efficiency and adaptability of design. Recently a specific size-dependent behavior for piezoelectric materials, known as flexoelectric effect, has drawn a great deal of attention. It is proven that this effect, which is resulted by coupling between the strain field and electric polarization, is of significant importance in structures with nano dimensions. This paper is carried out to investigate the vibrations and instability analysis of fluid-conveying piezoelectric nanotubes on the basis of flexoelectricity approach. The fluid-conveying nanotubes made for drug delivery targets are commonly in contact with soft tissues, which could be modeled as a Kelvin-Voigt foundation. The nonlocal strain gradient theory (NSGT) constitutive relations are employed in order to model the problem. An appropriate electric potential distribution is determined using the Maxwell's equation and Gauss's law. The Euler-Bernoulli beam theory and slip boundary conditions are exploited to derive the governing fluid-structure interaction (FSI) equation, which contains flexoelectric and surface effect terms. Galerkin's principle is hired to discretize the equation leading to an eigenvalue problem. Afterwards, the obtained characteristic equation is solved straightforwardly to gain the eigenvalues. The instability of the nanotube is investigated throughout presenting the eigenvalue diagrams. Some illustrations are employed to analyze the effect of different involved parameters on the vibrations and instability behavior of the system. The reported results in the numerical section of the paper may be helpful to achieve an efficient and accurate design of fluid-conveying nanotubes.

Flow-induced vibration analysis of a vehicle's front side window glass

This study analyses the flow-induced vibration of a car's front side window glass. The following working steps were carried out: experimental modal analysis to yield the dynamic characteristics of the system; wind tunnel experiments and corresponding numerical simulations with a computational fluid dynamics (CFD) code to acquire the pressure field including the fluctuations on the side glass; and a MATLAB implementation of the vibration velocity response calculated with the Corcos model and Mellen elliptical model. The MATLAB model calculates the averaged vibration velocity response by means of the pressure loading from the wind tunnel test or from the CFD simulations as well as by means of the result of the experimental modal analysis. The hereby calculated vibration response of the side glass has been validated by the results of laser Doppler vibrometer measurements in the wind tunnel. Through parameter study with the MATLAB algorithm, it was found that flow convective velocity with U c = 0.6*U, flow decay rates with α x = 0.1 and α z = 0.77 could be considered as the suitable values for the structure vibration velocity response calculation in this type of flow with a low Mach number.

Flow-induced vibration and stability analysis of carbon nanotubes based on the nonlocal strain gradient Timoshenko beam theory

A nonlocal strain gradient Timoshenko beam model is developed to study the vibration and instability analysis of the carbon nanotubes conveying nanoflow. The governing equations of motion and boundary conditions are derived by employing Hamilton’s principle, including the effects of moving fluid, material length scale and nonlocal parameters, Knudsen number and gravity force. The material length scale and nonlocal parameters are considered, in order to take into account the size effects. Also, to consider the small-size effects on the flow field, the Knudsen number is used as a discriminant parameter. The Galerkin approach is chosen to analyze the governing equations under clamped–clamped, clamped–hinged and hinged–hinged boundary conditions. It is found that the natural frequency and critical fluid velocity can be decreased by increasing the nonlocal parameter or decreasing the material length scale parameter. Furthermore, it is revealed that the critical flow velocity does not affected by two size-dependent parameters and various boundary conditions in the free molecular flow regime.

Nonproprietary Flow-Induced Vibration Analysis of San Onofre Nuclear Generating Station Replacement Steam Generators to ASME Code Section III Appendix N

Flow-induced vibration analysis of the San Onofre Nuclear Generating Station (SONGS) replacement steam generators (RSG) is made using nonproprietary public data for these steam generators on the Nuclear Regulatory Commission public web site (www.NRC.gov). The analysis uses the methodology of Appendix N Section III of the ASME Boiler and Pressure Vessel Code, Subarticle N-1300 Flow-Induced Vibration of Tubes and Tube Banks. First, the tube geometry is assembled, and overall flow and performance parameters are developed at 100% design flow; then, the analysis is made to determine the flow velocity in the gap between tubes and tube natural frequencies and mode shapes. Finally, the mass damping and reduced velocity for tubes on the U bend are assembled and plotted on the ASME code Figure N-11331-4 fluid elastic stability diagram.

Numerical analysis of shell-side flow-induced vibration of elastic tube bundle in heat exchanger

The responses of the flow-induced vibration of an elastic tube bundle subjected to the shell-side cross flow are investigated in this paper. The weak coupling method and the fluid solid interface are used to solve the fluid-structure interaction problem with consideration of the geometry and physical natures. The effects of the shell-side fluid flow velocity and the structural parameters on the flow-induced vibration are discussed. Numerical results demonstrate that the vibration frequency and amplitude at the monitor points increase with the increase of the shell-side water inlet velocity in all directions. The wall thickness and the external diameter of the elastic tube bundle have significant effects on the responses of the flow-induced vibration. The structural parameters affect the vibration frequency and amplitude, and the vibration equilibrium position in the water flow direction. The vibration frequency decreases with the increase of the tube external diameter. In addition, the vibration in the water flow direction has a lower equilibrium position when the elastic tube bundle has a larger wall thickness or smaller external diameter.

Analysis of flow-induced vibration of a magnetic head actuator with a linear protrusion structure

Analysis of flow-induced vibration of a magnetic head actuator with a linear protrusion structure

Numerical analysis of Flow-Induced Vibration for Collision of Two Side-by-Side Circular Cylinders in Close Arrangement

We, in this paper, present numerical results of flow-induced vibration for collision of two side-by-side circular cylinders which are mounted with the damper-spring systems. Two side-by-side circular cylinders are arranged at narrow spacing in the smooth flow. When the spacing is narrow, it is well-known from the experimental data that the flow behind stationary two circular cylinders becomes the gap flow. Then the two circular cylinders move along flow to the in-line and cross-flow directions in the complicated gap flow. In our simulation, the Scruton number of the circular cylinders is given as 1.0 and the Reynolds number is 20,000

Flow-induced vibration analysis of constricted artery models with surrounding soft tissue.

Arterial stenosis is a vascular pathology which leads to serious cardiovascular diseases. Blood flow through a constriction generates sound and vibration due to fluctuating turbulent pressures. Generated vibro-acoustic waves propagate through surrounding soft tissues and reach the skin surface and may provide valuable insight for noninvasive diagnostic purposes. Motivated by the aforementioned phenomena, vibration of constricted arteries is investigated employing computational models. The flow-induced pressure field in an artery is modeled as broadband harmonic pressure loading based on previous studies in the literature and applied on the inner artery wall. Harmonic analysis is performed for determining radial velocity responses on the outer surface of the models. Results indicate that stenosis severities higher than 70% lead to significant increase in response amplitudes, especially at high frequencies between 250 and 600 Hz. The findings agree well with experimental and theoretical results in the literature considering bending mode frequencies, amplitude scales, and mainly excited frequency ranges. It is seen that artery vibration is sensitive to the phase behavior of pressure loading but its effect becomes less significant with the presence of surrounding tissue. As the surrounding tissue thickness increases, radial velocity response amplitudes decrease but the effect of changes in tissue elastic modulus is more pronounced.

Nonlinear thermal and flow-induced vibration analysis of fluid-conveying carbon nanotube resting on Winkler and Pasternak foundations

Thermal-mechanical modeling of carbon nanotubes comes with nonlinear equations which are difficult to solve exactly and analytically with any existing general analytical method. However, in many cases of developing symbolic solutions for the nonlinear equations, recourse is made to approximate analytical methods in which their accuracies largely depend on the number of terms included in the solutions. In this work, analytical solutions are presented using differential transformation method with after-treatment technique for nonlinear analysis of thermal and flow-induced vibration of fluid-conveying carbon nanotube resting on Winkler and Pasternak foundations. The developed analytical solutions are used to investigate the effects of nonlocal parameter, Knudsen number, temperature, foundation parameters and boundary conditions on the dynamic behaviour of the single-walled nanotube. Also, the developed analytical solutions are verified with the numerical solutions and validated with experimental results. Good agreements are established between the results of the analytical solutions and the numerical solutions, and also between the results of the analytical solutions and the experimental results. The analytical solutions as presented in this work can serve as benchmarks for other methods of solutions of the problem. They can also provide a starting point for a better understanding of the relationship between the physical quantities of the problems.

Flow-induced vibration analysis of a helical coil steam generator experiment using large eddy simulation

This paper describes a numerical study of flow-induced vibration in a helical coil steam generator experiment conducted at Argonne National Laboratory in the 1980s. In the experiment, a half-scale sector model of a steam generator helical coil tube bank was subjected to still and flowing air and water, and the vibrational characteristics were recorded. The research detailed in this document utilizes the multi-physics simulation toolkit SHARP developed at Argonne National Laboratory, in cooperation with Lawrence Livermore National Laboratory, to simulate the experiment. SHARP uses the spectral element code Nek5000 for fluid dynamics analysis and the finite element code DIABLO for structural analysis. The flow around the coil tubes is modeled in Nek5000 by using a large eddy simulation turbulence model. Transient pressure data on the tube surfaces is sampled and transferred to DIABLO for the structural simulation. The structural response is simulated in DIABLO via an implicit time-marching algorithm and a combination of continuum elements and structural shells. Tube vibration data (acceleration and frequency) are sampled and compared with the experimental data. Currently, only one-way coupling is used, which means that pressure loads from the fluid simulation are transferred to the structural simulation but the resulting structural displacements are not fed back to the fluid simulation.

Numerical modeling of flow induced vibration of nuclear fuel rods

Flow induced vibration (FIV) plays an important role in many industrial applications, including nuclear energy. In a nuclear power plant, several components could experience FIV. However, among them, fuel rods are critical because of the combined effects of very slender shapes of the rods and hydrodynamic loads induced by the turbulent flow of the surrounding coolant fluid. In this article, a numerical study of a nuclear fuel rod system is performed using a combined computational fluid dynamics (CFD) and computational structural mechanic (CSM) approach. The selected rod system is representative of an experimental set-up consisting of a single and multiple fuel rods exhibiting strongly coupled non-linear behaviors. As a first step, an operational procedure is proposed to construct a numerical model of the rod to be used in the Fluid-structure interaction (FSI) simulations. The material properties of the model are tuned to match the experimental natural frequencies measured in free air. Despite the structural complexities present in the experiments, the natural frequencies of the rod are correctly reproduced, which is an essential step for the subsequent FIV analysis. Subsequently, the FSI computations are performed and the numerical results are processed to extract the modal parameters of the system in axial turbulent flow regime. Both, one and two rod systems are extensively studied for different flow velocities. The obtained results agree with the measurements and the theory.

Flow-induced vibration analysis of elastic propellers in a cyclic inflow: An experimental and numerical study

In this paper, the flow-induced vibrations of marine propellers in cyclic inflows are investigated both experimentally and numerically. A Laser-Doppler velocimetry (LDV) system is used to measure the axial flow velocity distributions produced by the seven-cycle wake screen in the water tunnel. A customized underwater slip ring and a single axis accelerometer sealed by silicon sealant are employed to measure the acceleration responses of rotating propeller blade. Numerical simulations of pressure fluctuations on the blades are performed using large eddy simulation (LES), while the forced vibrations of the propeller blades are obtained by a combined finite element and boundary element method. Experimental and numerical results are presented for two model propellers with the same geometries and different flexible properties, which show that the propeller blade vibrates at a frequency which is seven times as large as the axial passing frequency (APF) in the seven-cycle inflow. Moreover, the propeller blades are observed to resonance when the 7 APF excitation frequency is equal to the fundamental frequency of the propellers. The results indicate that both the inflow feature and the modal characteristic of blades contribute to flow-induced vibrations of elastic propellers.

Анализ влияния многофазного потока на механические колебания нефтегазосборного трубопровода Новопортовского нефтегазоконденсатного месторождения

Анализ влияния многофазного потока на механические колебания нефтегазосборного трубопровода Новопортовского нефтегазоконденсатного месторождения

Analysis of Flow-induced Vibration of Fluid Conveying Pipe with Elastic Support

Analysis of Flow-induced Vibration of Fluid Conveying Pipe with Elastic Support

Analysis of Flow-Induced Vibration Due to Stratified Wavy Two-Phase Flow

Fluctuating force induced by horizontal gas–liquid two-phase flow on 90 deg pipe bend at atmospheric pressure condition is considered. Analysis was conducted to develop a model which is capable of predicting the peak force fluctuation frequency and magnitudes, particularly at the stratified wavy two-phase flow regime. The proposed model was developed from the local instantaneous two-fluid model, and adopting guided acoustic theory and dynamic properties of one-dimensional (1D) waves to consider the collisional force due to the interaction between dynamic waves and structure. Comparing the developed model with experimental database, it was found that the main contribution of the force fluctuation due to stratified wavy flow is from the momentum and pressure fluctuations, and collisional effects. The collisional effect is due to the fluid–solid interaction of dynamic wave, which is named as the wave collision force. Newly developed model is capable of predicting the force fluctuations and dominant frequency range with satisfactory accuracy for the flow induced vibration (FIV) caused by stratified wavy two-phase flow in 52.5 mm inner diameter (ID) pipe bend.

Signal analysis of acoustic and flow-induced vibrations of BWR main steam line

The aim of this work is the signal analysis of acoustic waves due to phenomenon known as singing in Safety Relief Valves (SRV) of the main steam lines (MSL) in a typical BWR5. The acoustic resonance in SRV standpipes and fluctuating pressure is propagated from SRV to the dryer through the MSL. The signals are analyzed with a novel method based on the Multivariate Empirical Mode Decomposition (M-EMD). The M-EMD algorithm has the potential to find common oscillatory modes (IMF) within multivariate data. Based on this fact, we implement the M-EMD technique to find the oscillatory mode in BWR considering the measurements obtained collected by the strain gauges located around the MSL. These IMF, analyzed simultaneously in time, allow obtaining an estimation of the effects of the multiple-SRV in the MSL. Two scenarios are analyzed: the first is the signal obtained before the installation of the acoustic dampers (ASB), and the second, the signal obtained after installation. The results show the effectiveness of the ASB to damp the strong resonances when the steam flow increases, which represents an important reduction in the acoustic loads to the steam dryer.

Analysis of flow-induced vibrations in turbomachinery by mapping of complex fluid pressures

In this paper we introduce a mapping procedure which facilitates the simulation of flow-induced vibrations in turbomachinery. The transient steady state pressure fluctuations in the flow field (which excite vibrations) are computed in the frequency domain by what are generally referred to as “harmonic CFD” methods where the pressure oscillations are expressed by complex amplitudes. They are mapped using the Fraunhofer software FSIMapper to a structural vibration analysis. A main focus lies in the provision of mapping methods for cyclic symmetric models. The process provides a fast numerical assessment of flow-induced vibrations where the resulting vibration amplitudes can be used for realistic fatigue estimations of flow-excited turbine components. The procedure is applied to a ceramic impeller of a micro gas turbine.