Parametric Behaviour Of A Vortex-Induced Vibration Model Of Cylinders With 2 Degrees Of Freedom Using A Wake Oscillator

2021 ◽  
pp. 1-57
Author(s):  
Rafael Fehér ◽  
Juan P. J. Avila
Keyword(s):  
Experimental Data ◽  
Degrees Of Freedom ◽  
Flow Direction ◽  
Damping Ratio ◽  
Cross Flow ◽  
Maximum Amplitude ◽  
Experimental Conditions ◽  
Tuning Parameters ◽  
Wake Oscillator ◽  
Mass Ratios

Abstract A model recently proposed by Qu and Metrikine (2020) to predict Vortex-Induced Vibrations of a rigid cylinder elastically mounted with 2 Degrees of Freedom is analyzed and its response is compared with different experimental responses presented in the literature. As the authors themselves pointed out in their work, a comprehensive parametric sensitivity analysis and calibration with more experiments must still be done using this model. The model uses only one equation for the wake oscillator, with a total of three tuning parameters. One database with the tuning parameters for different mass ratios and damping ratios is presented. This will provide a set of pre-defined tuning parameters for different experimental conditions. Thus, the task of trial and error to find the most suitable values for these parameters for a given application is facilitated including the information of the parametric sensibility. After conducting a performance analysis, the model shows to be efficient in predict the maximum amplitude of vibration in the cross-flow direction when compared to experimental data for mass ratios varying from 2.36 to 12.96. For mass ratios higher than 7.91, the model do not predict the correct reduced velocity where the lock-in range initiates. The results are in good agreement with experimental data for damping ratios from 0.002 to 0.4, predicting correct values for the reduced amplitude in both directions. The model shows to be less sensitive to variations in the damping ratio when compared to variations in the mass ratio.

The Numerical Research of Two-Degrees-of-Freedom Vortex-Induced Vibrations of Circular Cylinders

2012 ◽  
Vol 204-208 ◽  
pp. 4598-4601
Author(s):  
Jie Li Fan ◽  
Wei Ping Huang
Keyword(s):  
Degrees Of Freedom ◽  
Amplitude Ratio ◽  
Flow Direction ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Two Degrees Of Freedom ◽  
Line Frequency ◽  
Ansys Cfx ◽  
Vortex Induced Vibrations ◽  
Lock In

The two-degrees-of-freedom of vortex-induced vibration of circular cylinders is numerically simulated with the software ANSYS/CFX. The VIV characteristic, in the two different conditions (A/D=0.07 and A/D=1.0), is analyzed. When A/D is around 0.07, the amplitude ratio of the cylinder’s VIV between in-line and cross-flow direction in the lock-in is lower than that in the lock-out. The in-line frequency is twice of that in cross-flow direction in the lock-out, but in the lock-in, it is the same as that in cross-flow direction and the same as that of lift force. When A/D is around 1.0, the amplitude ratio of the VIV between in-line and cross-flow in the lock-in is obviously larger than that in the lock-out. Both in the lock-in and in the lock-out, the in-line frequency is twice of that in cross-flow direction.

scholarly journals Flow-induced vibrations of a rotating cylinder

2014 ◽  
Vol 740 ◽  
pp. 342-380 ◽  
Author(s):  
Rémi Bourguet ◽  
David Lo Jacono
Keyword(s):  
Symmetry Breaking ◽  
Flow Direction ◽  
Cross Flow ◽  
Maximum Amplitude ◽  
Rotating Cylinder ◽  
Free Vibrations ◽  
Cylinder Surface ◽  
Single Vortex ◽  
Flow Induced Vibrations ◽  
The Impact

AbstractThe flow-induced vibrations of a circular cylinder, free to oscillate in the cross-flow direction and subjected to a forced rotation about its axis, are analysed by means of two- and three-dimensional numerical simulations. The impact of the symmetry breaking caused by the forced rotation on the vortex-induced vibration (VIV) mechanisms is investigated for a Reynolds number equal to $100$, based on the cylinder diameter and inflow velocity. The cylinder is found to oscillate freely up to a rotation rate (ratio between the cylinder surface and inflow velocities) close to $4$. Under forced rotation, the vibration amplitude exhibits a bell-shaped evolution as a function of the reduced velocity (inverse of the oscillator natural frequency) and reaches $1.9$ diameters, i.e. three times the maximum amplitude in the non-rotating case. The free vibrations of the rotating cylinder occur under a condition of wake–body synchronization similar to the lock-in condition driving non-rotating cylinder VIV. The largest vibration amplitudes are associated with a novel asymmetric wake pattern composed of a triplet of vortices and a single vortex shed per cycle, the ${\rm T} + {\rm S}$ pattern. In the low-frequency vibration regime, the flow exhibits another new topology, the U pattern, characterized by a transverse undulation of the spanwise vorticity layers without vortex detachment; consequently, free oscillations of the rotating cylinder may also develop in the absence of vortex shedding. The symmetry breaking due to the rotation is shown to directly impact the selection of the higher harmonics appearing in the fluid force spectra. The rotation also influences the mechanism of phasing between the force and the structural response.

scholarly journals Fluid nonlinearities effect on wake oscillator model performance

2018 ◽  
Vol 148 ◽  
pp. 04002 ◽  
Author(s):  
Victoria Kurushina ◽  
Ekaterina Pavlovskaia
Keyword(s):  
Structural Damage ◽  
Degrees Of Freedom ◽  
Model Performance ◽  
Cross Flow ◽  
Resonance State ◽  
Oscillator Model ◽  
Mass Ratio ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Wide Range

Vortex-induced vibrations (VIV) need to be accounted for in the design of marine structures such as risers and umbilicals. If a resonance state of the slender structure develops due to its interaction with the surrounding fluid flow, the consequences can be severe resulting in the accelerated fatigue and structural damage. Wake oscillator models allow to estimate the fluid force acting on the structure without complex and time consuming CFD analysis of the fluid domain. However, contemporary models contain a number of empirical coeffcients which are required to be tuned using experimental data. This is often left for the future work with the opened question on how to calibrate a model for a wide range of cases and find out what is working and is not. The current research is focused on the problem of the best choice of the fluid nonlinearities for the base wake oscillator model [1] in order to improve the accuracy of prediction for the cases with mass ratios around 6.0. The paper investigates six nonlinear damping types for two fluid equations of the base model. The calibration is conducted using the data by Stappenbelt and Lalji [2] for 2 degrees-of-freedom rigid structure for mass ratio 6.54. The conducted analysis shows that predicted in-line and cross-flow displacements are more accurate if modelled separately using different damping types than using only one version of the model. The borders of application for each found option in terms of mass ratio are discussed in this work, and appropriate recommendations are provided.

A Wake Oscillator With Frequency Dependent Tuning Coefficients for the Modeling of VIV

2008 ◽  
Author(s):  
R. H. M. Ogink ◽  
A. V. Metrikine
Keyword(s):  
Free Vibration ◽  
Structural Equation ◽  
Maximum Amplitude ◽  
Good Prediction ◽  
Convolution Integral ◽  
Coupling Term ◽  
Tuning Parameters ◽  
Wake Oscillator ◽  
Wide Range ◽  
Lock In

A wake oscillator for the modeling of vortex-induced vibration is presented in which the coupling term between the oscillator and the structural equation is written in the form of a convolution integral. In this way the potential to tune the model to measurements is extended greatly. The model is tuned to forced vibration measurements. Then, without changing the tuning parameters, the model is applied to simulate free vibration experiments. A good prediction of the maximum amplitude and the width of the lock-in range is found over a wide range of mass and damping ratios.

Vortex-induce Vibrations of Two Degrees of Freedom Sprung Cylinder with a Rotational Nonlinear Energy Sink (r-nes): a Numerical Investigation

2021 ◽  
Author(s):  
Dongyang Chen ◽  
Chaojie Gu ◽  
Ruihua Zhang ◽  
Jiaying Liu ◽  
Dian Guo ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Nonlinear Energy Sink ◽  
High Mass ◽  
Oscillator Model ◽  
Two Degrees Of Freedom ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Mass Ratios ◽  
Energy Sink ◽  
Nonlinear Energy

Abstract Vortex-induced vibration (VIV) is a common fluid-structure interaction (FSI) phenomenon in the field of wind engineering and marine engineering. The large-amplitude VIV has a marked impact on the slender structure in fluids, at times even destructive. To study how the VIV can be controlled, the dynamics of a rigid cylinder attached to a rotational nonlinear energy sink (R-NES) is investigated in this paper. This is done using a two degrees of freedom (2-DOF) Van der Pol wake oscillator model adapted to consider a coupled vibration in cross-flow and streamwise directions. The governing equation of R-NES are coupled to the wake oscillator model, hence a flow-cylinder-NES coupled system is established. While exploring the dynamics of the cylinders with different mass ratios under the action of R-NES, it was found that the R-NES deliver better performance in suppressing the VIV of a cylinder with high mass ratios than that of a low mass ratios cylinder. The effect of the distinct parameters of R-NES on VIV response was also systematically investigated in this study. The results indicate that higher mass parameter and rotation radius can lead to improved performance, while the effect of the damping parameter is complex, and appears to be linked to the mass ratio of the column structure.

Vortex-Induced Vibration Experiment Research of Two Cylinders in Tandem Arrangement

2013 ◽  
Author(s):  
Zhuang Kang ◽  
Weixing Liu ◽  
Wei Qin
Keyword(s):  
Degrees Of Freedom ◽  
Flow Direction ◽  
Cross Flow ◽  
Near Wake ◽  
Tandem Arrangement ◽  
Vortex Induced Vibration ◽  
Wake Interference ◽  
Vibration Experiment ◽  
Low Mass ◽  
Far Wake

The vortex-induced vibration of tandem arrangement of two cylinders compared with the single cylinder is more complicated, The double cylinder arranged in tandem, which is free to move in two degrees of freedom respectively, and which has low mass and damping. The present study shows that a critical centre-to-centre spacing can be used to distinguish the far and near wake interference. The streams in this test were uniform flow, ranging from 0.2m/s to 0.8m/s with the interval of 0.1m/s. The Re numbers are ranging from 22000 to 88000. The mass ratio of cylinder is low. For far wake interference, the downstream cylinder shows large amplitudes of response, therefore the wake induced vibration (WIV) is found. For near wake interference, both the upstream cylinder and downstream cylinder are exposed to an evident phenomenon of VIV, but the amplitude of upstream and downstream are less than that of single cylinders in cross-flow direction and in-line direction. We found the critical spacing to be 3.4 to 4.9.

A Single-Flexible-Cylinder Analysis for the Fluidelastic Instability of an Array of Flexible Cylinders in Cross-Flow

1986 ◽  
Vol 108 (2) ◽  
pp. 193-199 ◽  
Author(s):  
S. J. Price ◽  
M. P. Paidoussis
Keyword(s):  
Experimental Data ◽  
Flow Direction ◽  
Cross Flow ◽  
Critical Flow ◽  
Flexible Cylinder ◽  
Stagnation Region ◽  
Critical Flow Velocity ◽  
Array Pattern ◽  
Damping Parameter ◽  
Fluid Damping

A quasi-static fluidelastic analysis is developed for a single flexible cylinder surrounded by rigid cylinders and subject to cross-flow. Although the analysis is quasi-static, it includes a frequency-dependent term which arises because of flow retardation around the front stagnation region of the cylinder. The combined effect of this flow retardation and of the fluid force field is to produce, for some intercylinder patterns of motion, a negative fluid damping, acting in the sense normal to the flow direction. Using this analysis, the effect of array pattern of the adjacent rigid cylinders is investigated, and it is shown that for some geometries a single flexible cylinder will become unstable while for others it will not. For those array patterns which the theory indicates to be potentially unstable, the variation of critical flow velocity with mass-damping parameter is obtained and compared with available experimental data. In general, the comparison is good, indicating the validity of this analysis.

A Wake Oscillator Model With Nonlinear Coupling for the VIV of Rigid Cylinder Constrained to Vibrate in the Cross-Flow Direction

2016 ◽  
Author(s):  
Y. Qu ◽  
A. V. Metrikine
Keyword(s):  
Forced Vibration ◽  
Flow Direction ◽  
Cross Flow ◽  
Added Mass ◽  
Oscillator Model ◽  
Nonlinear Coupling ◽  
Rigid Cylinder ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Good Agreement

In this paper a new wake oscillator model with nonlinear coupling term is proposed to model the vortex-induced vibration of an elastically supported rigid cylinder constrained to vibrate in the cross-flow direction. The superiority of this new model lies in its ability to satisfy at the same time both free and forced vibration experiments. The new wake oscillator model is based on an existing van der Pol wake oscillator model and nonlinear coupling terms are added to improve its performance in the modelling of forced vibration. The tuning of this new model to the forced vibration shows good agreement with experiments in terms of the added damping but failed to capture the negative added mass at high reduced velocities. To eliminate this discrepancy the model is further enhanced by relaxing the assumption of constant potential added mass. Using the parameters obtained from the forced vibration experiments, the free vibration simulation is conducted and results are compared with the experiments. Comparison indicates good agreement between simulation and experiments, and the main features of VIV are captured.

scholarly journals Zeolite NaP1 Functionalization for the Sorption of Metal Complexes with Biodegradable N-(1,2-dicarboxyethyl)-D,L-aspartic Acid

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2518
Author(s):  
Dorota Kołodyńska ◽  
Yongming Ju ◽  
Małgorzata Franus ◽  
Wojciech Franus
Keyword(s):  
Experimental Data ◽  
Aspartic Acid ◽  
Ph Value ◽  
Complexing Agents ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Modified Zeolite ◽  
X Ray ◽  
Slow Release Fertilizers ◽  
Pseudo Second Order

The possibility of application of chitosan-modified zeolite as sorbent for Cu(II), Zn(II), Mn(II), and Fe(III) ions and their mixtures in the presence of N-(1,2-dicarboxyethyl)-D,L-aspartic acid, IDHA) under different experimental conditions were investigated. Chitosan-modified zeolite belongs to the group of biodegradable complexing agents used in fertilizer production. NaP1CS as a carrier forms a barrier to the spontaneous release of the fertilizer into soil. The obtained materials were characterized by Fourier transform infrared spectroscopy (FTIR); surface area determination (ASAP); scanning electron microscopy (SEM-EDS); X-ray fluorescence (XRF); X-ray diffraction (XRD); and carbon, hydrogen, and nitrogen (CHN), as well as thermogravimetric (TGA) methods. The concentrations of Cu(II), Zn(II), Mn(II), and Fe(III) complexes with IDHA varied from 5–20 mg/dm3 for Cu(II), 10–40 mg/dm3 for Fe(III), 20–80 mg/dm3 for Mn(II), and 10–40 mg/dm3 for Zn(II), respectively; pH value (3–6), time (1–120 min), and temperature (293–333 K) on the sorption efficiency were tested. The Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin adsorption models were applied to describe experimental data. The pH 5 proved to be appropriate for adsorption. The pseudo-second order and Langmuir models were consistent with the experimental data. The thermodynamic parameters indicate that adsorption is spontaneous and endothermic. The highest desorption percentage was achieved using the HCl solution, therefore, proving that method can be used to design slow-release fertilizers.

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