Experimentally-Tuned Finite Element Model of Flow-Induced Vibrations in a Square Tube Bundle Subjected to Cross-Flow

2012 ◽  
Author(s):  
Y. A. Khulief ◽  
S. A. Said
Keyword(s):  
Finite Element ◽  
Dynamic Model ◽  
Complex Dynamics ◽  
Tube Bundle ◽  
Cross Flow ◽  
Element Model ◽  
Analytical Models ◽  
Test Rig ◽  
Flow Induced Vibration ◽  
Flow Induced Vibrations

It has been recognized that modeling of the complex dynamics of fluidelastic forces, that give rise to vibrations of tube bundles, requires a comprehensive dynamic model of high fidelity based on experimental insight. Accordingly, the prediction of the flow-induced vibration due to unsteady cross-flow can be greatly aided by semi-analytical models, in which some coefficients are determined experimentally. In this paper, the elastodynamic model of the tube array is formulated using the finite element approach, wherein each tube is modeled by a set of finite tube-elements. The interaction between tubes in the bundle is represented by fluidelastic coupling forces, which are defined in terms of the multi-degree-of-freedom elastodynamic behavior of each tube in the bundle. A laboratory test rig with an instrumented square bundle is constructed to measure the fluidelastic coefficients used to tune the developed dynamic model. The test rig admits two different test bundles; namely the inline-square and 45° rotated-square tube arrays. Measurements were conducted to identify the flow-induced dynamic coefficients. The developed scheme was utilized in predicting the onset of flow-induced vibrations, and results were examined in the light of TEMA predictions. The comparison demonstrated that TEMA guidelines are more conservative in the two configurations considered.

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part II: Experimental Investigation

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
S. A. Al-Kaabi ◽  
Y. A. Khulief ◽  
S. A. Said
Keyword(s):  
Heat Exchangers ◽  
Complex Dynamics ◽  
Cross Flow ◽  
Analytical Models ◽  
Test Rig ◽  
Flow Induced Vibration ◽  
Tube Arrays ◽  
Tube Bundles ◽  
Flow Induced Vibrations ◽  
The Mathematical Model

It has become evident that the modeling of the complex dynamics of fluidelastic forces that give rise to vibrations of tube bundles requires a great deal of experimental insight. Accordingly, the prediction of the flow-induced vibration due to unsteady cross-flow can be greatly aided by semi-analytical models, in which some coefficients are determined experimentally. A laboratory test rig with an instrumented test bundle is constructed to measure the fluidelastic coefficients to be used in conjunction with the mathematical model derived in Part I of this paper. The test rig admits two different test bundles, namely, the inline-square and 45deg rotated-square tube arrays. Measurements were conducted to identify the flow-induced dynamic coefficients. The developed scheme was utilized in predicting the onset of flow-induced vibrations in two configurations of tube bundles, and results were examined in the light of Tubular Exchange Manufacturers Association (TEMA) predictions. The comparison demonstrated that TEMA guidelines are more conservative in the two configurations considered.

Investigations of In-Plane Fluidelastic Instability in a Multi-Span U-Bend Tube Bundle: Tests in Air Flow

2017 ◽  
Author(s):  
Paul Feenstra ◽  
Teguewinde Sawadogo ◽  
Bruce Smith ◽  
Victor Janzen ◽  
Helen Cothron
Keyword(s):  
Steam Generator ◽  
Tube Bundle ◽  
Air Flow ◽  
Cross Flow ◽  
Test Rig ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Fluidelastic Instability ◽  
Air Blower ◽  
R 134A

The tubes in the U-bend region of a recirculating type of nuclear steam generator are subjected to cross-flow of a two-phase mixture of steam and water. There is a concern that these tubes may experience flow-induced vibration, including the damaging effects of fluidelastic instability. This paper presents an update and results from a series of flow-induced vibration experiments performed by Canadian Nuclear Laboratories for the Electric Power Research Institute (EPRI) using the Multi-Span U-Bend test rig. In the present experiments, the main focus was to investigate fluidelastic instability of the U-tubes subjected to a cross-flow of air. The tube bundle is made of 22 U-tubes of 0.5 in (12.7 mm) diameter, arranged in a rotated triangular configuration with a pitch-over-diameter ratio of 1.5. The test rig could be equipped with variable clearance flat bar supports at two different locations to investigate a variety of tube and support configurations. The primary purpose of the overall project is to study the effect of flat bar supports on ‘in plane’ (‘streamwise’) instability in a U-tube bundle with realistic tube-to-support clearances or preloads, and eventually in two-phase flow conditions. Initially, the test rig was designed for tests in air-flow using an industrial air blower. Tests with two-phase Freon refrigerant (R-134a) will follow. This paper describes the test rig, experimental setup, and the challenges presented by simulating an accurate representation of current steam generator designs. Results from the first series of tests in air flow are described.

Accurate Evaluation of Bolt and Clamped Members Stiffnesses Of Bolted Joints

2021 ◽  
Author(s):  
Rashique Iftekhar Rousseau ◽  
Abdel-Hakim Bouzid ◽  
Zijian Zhao
Keyword(s):  
Finite Element ◽  
Joint Stiffness ◽  
Element Model ◽  
Fe Analysis ◽  
Bolted Joints ◽  
Analytical Models ◽  
Fe Modeling ◽  
Bolted Joint ◽  
A New Technique ◽  
External Loads

Abstract The axial stiffnesses of the bolt and clamped members of bolted joints are of great importance when considering their integrity and capacity to withstand external loads and resist relaxation due to creep. There are many techniques to calculate the stiffnesses of the joint elements using finite element (FE) modeling, but most of them are based on the displacement of nodes that are selected arbitrarily; therefore, leading to inaccurate values of joint stiffness. This work suggests a new method to estimate the stiffnesses of the bolt and clamped members using FE analysis and compares the results with the FE methods developed earlier and also with the existing analytical models. A new methodology including an axisymmetric finite element model of the bolted joint is proposed in which the bolts of different sizes ranging from M6 to M36 are considered for the analysis to generalize the proposed approach. The equivalent bolt length that includes the contribution of the thickness of the bolt head and the bolt nominal diameter to the bolt stiffness is carefully investigated. An equivalent bolt length that accounts for the flexibility of the bolt head is proposed in the calculation of the bolt stiffness and a new technique to accurately determine the stiffness of clamped members are detailed.

scholarly journals Modelling a Cracked Beam Structure Using the Finite Element Displacement Method

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Hui Long ◽  
Yilun Liu ◽  
Changzheng Huang ◽  
Weihui Wu ◽  
Zhaojun Li
Keyword(s):  
Finite Element ◽  
Dynamic Model ◽  
Structural Parameters ◽  
Element Model ◽  
Beam Element ◽  
The Finite Element Method ◽  
Displacement Method ◽  
Beam Structure ◽  
Cracked Beam ◽  
Local Flexibility

A new model is presented for studying the effects of crack parameters on the dynamics of a cracked beam structure. The model is established by the finite element displacement method. In particular, the stiffness matrix of the cracked beam element is firstly derived by the displacement method, which does not need the flexibility matrix inversion calculation compared with the previous local flexibility approaches based on the force method. Starting with a finite element model of cracked beam element, the equation of strain energy of a cracked beam element is formed by the displacement method combined with the linear fracture mechanics. Then, based on the finite element method, the dynamic model of the cracked beam structure is obtained. The results show that the dynamic model discovers the internal relation between the dynamic characteristics of cracked beam structure and structural parameters, material parameters, and crack parameters. Finally, an example is presented to validate the proposed dynamic model.

Rotordynamics Analysis: Experimental and Numerical Investigations

2003 ◽  
Author(s):  
Jean-Jacques Sinou ◽  
David Demailly ◽  
Cristiano Villa ◽  
Fabrice Thouverez ◽  
Michel Massenzio ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Critical Speed ◽  
Experimental Tests ◽  
Element Model ◽  
Test Rig ◽  
Turbofan Engine ◽  
Rotating Structure ◽  
Vibration Problems ◽  
The Finite Element Model

This paper presents a research devoted to the study of vibration problems in turbofan application. Several numerical and experimental tools have been developed. An experimental test rig that simulates the vibrational behavior of a turbofan engine is presented. Moreover, a finite element model is used in order to predict the non-linear dynamic behavior of rotating machines and to predict the first critical speed of engineering machine. A comparison between the experimental tests and the numerical model is conducted in order to evaluate the critical speed of the rotating structure and to update the finite element model.

Improved Correlation of Measured and Predicted Hysteresis Loops in a Multiaxial Fretting Fatigue Test Rig for Spline Couplings

2007 ◽  
Vol 7-8 ◽  
pp. 37-42
Author(s):  
D. Houghton ◽  
P.M. Wavish ◽  
Edward J. Williams ◽  
Sean B. Leen
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Fatigue Test ◽  
Hysteresis Loops ◽  
Element Model ◽  
Fretting Fatigue ◽  
Global Model ◽  
Test Rig ◽  
Force Displacement

This paper investigates the comparison of the measured and predicted force-displacement loops of a multiaxial representative fretting fatigue test rig for aeroengine spline couplings. A local finite element model of the fretting specimen and the fretting bridge is outlined. A more extensive model of the fretting test rig is then introduced. This global model also includes the loading structures. The model captures the compliance of the fretting test rig and improves the correlation of the observed hysteresis. This method allows the slip amplitude at the contacts to be quantified.

Vibration Excitation Forces in a Rotated Triangular Tube Bundle Subjected to Two-Phase Cross Flow

2010 ◽  
Author(s):  
H. Senez ◽  
N. W. Mureithi ◽  
M. J. Pettigrew
Keyword(s):  
Steam Generator ◽  
Tube Bundle ◽  
Cross Flow ◽  
Fretting Wear ◽  
Experimental Program ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Fluid Forces ◽  
Vibration Excitation

Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting wear or fatigue. Detailed flow and vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. Studies on this subject have already been done, providing results on flow regimes, fluidelastic instabilities, and turbulence-induced vibration. The spectrum of turbulence-induced forces has usually been expected to be similar to that in single-phase flow. However, a recent study, using tubes with a diameter larger than that in a real steam generator, showed the existence of significant quasi-periodic forces in two-phase flow. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air-water cross-flow, to simulate two-phase mixtures. The tube bundle here has the same geometry as that of a real steam generator. The quasi-periodic forces have now also been observed in this tube bundle. The present work aims to understand turbulence-induced forces acting on the tube bundle, providing results on drag and lift force spectra and their behaviour according to flow parameters, and describing their correlations. Detailed experimental test results are presented in this paper. Comparison is also made with previous measurements with larger diameter tubes. The present results suggest that quasi-periodic fluid forces are not uncommon in tube arrays subjected to two-phase cross-flow.

Examination of Response of a Skewed Steel Bridge Superstructure During Deck Placement

2003 ◽  
Vol 1845 (1) ◽  
pp. 66-75 ◽  
Author(s):  
Elizabeth K. Norton ◽  
Daniel G. Linzell ◽  
Jeffrey A. Laman
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Analytical Models ◽  
Levels Of Analysis ◽  
Steel Bridge ◽  
Bridge Superstructure ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Skewed Bridge

The response of a 74.45-m (244-ft 0-in.) skewed bridge to the placement of the concrete deck was monitored to compare measured and predicted behavior. This comparison was completed to ( a) determine theoretical deflections and rotations with analytical models for comparison to actual deformations monitored during construction; ( b) compare the results of various levels of analysis to determine the adequacy of the methods; and ( c) examine variations on the concrete placement sequence to determine the most efficient deck placement methods. Two levels of analysis were used to achieve the objectives. Level 1 was a two-dimensional finite element grillage model analyzed with STAAD/Pro. Level 2 was a three-dimensional finite element model analyzed with SAP2000. These studies are discussed and findings are presented.

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